Re: [pinhole-discussion] Westmark Industries/Raytex

[Guillermo]

Stewart,

You lost it by less than a buck, in cases like this I sometimes email to the
seller off eBay and ask him if he is willing to sell another one at the
closing bid price, sometimes they agree.

What about getting a body cap and making your own pinhole body cap.  I did a
google search and got few places in USA and UK that sell them.  There are
some being auctioned at eBay at the moment, is this  a cap for your camera?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2931931932&category=29965
it is just around $5, it closes in 2.5hrs, BTW.

Guillermo

- Original Message -
From: "Stewart C.Russell" 


> Does anyone use equipment made by Helmut Weber/Westmark Industries/Raytex,
from Perth, Western Australia?
>
> I notice he/they make an Leica screw pinhole body cap. I don't know about
pricing or availability -- I just got outbid for one on eBay
>
> Their website seems to be a little out of date:
<http://www.geocities.com/westmarkwa/wme1.htm>.
>
> It has the same angle of view as a 25mm lens, so if you've got the
Voigtlaender Snapshot Skopar 25/4, you've got the viewfinder for it.

Re: [pinhole-discussion] WPPD 2003

[Guillermo]

- Original Message -
From: "Richard Heather" 


> Actually it seems that there are 1159 submissions!

That is right Richard, but only 1082 "hang" in the gallery, the remainder 77
were rejected for not complying with the submission rules (i.e., only one
image per participant) or simply because there was no actual image in the
submission, in which case the participant was notified and invited to
re-submit the image.

Guillermo

Re: [pinhole-discussion] Pinhole tunnels (was Vegan pinhole)

[Guillermo]

- Original Message -
From: "Michael Healy" 
>
> I have tried using an old Cronos shutter on my 7x17" but it vignettes
> something fierce. Its diameter is about 18mm, but it's also about 15mm
deep.
> I think it was designed for a 110 camera on monorail. I have a bigger
> shutter on the way, so the problem is going away; but is there some
formula
> handy for figuring out how to anticipate the wall's thickness so it falls
> outside the pinhole's (120 degree?) sweeping view? I barely passed
geometry
> to begin with, and now that half the brain cells have been killed off over
> the years, there can't be any memory of it left anyway.
>
> Any thoughts?

There are many things to consider, one is: do you really need 120 degrees of
view (DV)?  the DV, BTW,  depends on the diagonal of the format and the
focal length of your camera.

Now, assuming you do need 120 DV, the formula to anticipate the "wall's
thickness" would depend on where inside the shutter you mount your pinhole.
There are 3 cases:

1- installing the pinhole right midway inside the shutter:  In this case the
"wall thickness" has to be smaller than 1.732 times the diameter of the
shutter's opening (in case you ask  1.732 = Tan[120/2]).  In your example,
with a shutter 18mm in diameter, the "wall thickness" should not be more
than  18 / 1.732 , in other words it can not be thicker than 10.39mm

2- installing the pinhole anywhere from flush with the rear of the shutter
to just before midway inside the it.  In this case, if we call "I" the
distance from the rear of the shutter to where the pinhole is installed and
"W" the diameter of the shutter, the "wall thickness" has to be less than:

[W / (2 * Tan(120/2))] + I

3- installing the pinhole anywhere from flush with the front of the shutter
to just before midway inside the it.  In this case, if we call "F" the
distance from the front of the shutter to where the pinhole is installed and
"W" the diameter of the shutter, the "wall thickness" has to be less than:

[W / (2 * Tan(120/2))] + F

Case 1 is a particular case of both Case 2 and 3.  The 3 Cases could
probably be combined into 1 single formula, but at this point of the night
my brain cells are not functioning quite well, so I better hit the pillow.

> Mike Healy
> Tempe (110 degrees in the shade), AZ

Guillermo
(my tomato plants almost die last nite when temp went around freezing mark)
(It will be warmer tonite 42F.life in the great white north  :-)

Re: [pinhole-discussion] Vegan pinhole

[Guillermo]

- Original Message -
From: "Michael Healy" 


> Say, Guillermo. The local supermarkets are packaging four bell peppers
> together now in special clear plastic bags. You get a green one, a yellow
> one, a red one, and an orange one. Think you could make a pinhole happen
> with this?

Sure, I'd take the red one, remove the seeds, mount a pinhole and load it
with MGIV.  The red would act as safelight.  I'd then grill the other ones,
peel the skin, julien them add some balsamic, olive oil, oregano
(you-know-what-I'm-saying).

> Also, have you seen the microwavable baking potatoes yet?

You don't expect a pinholer to use microwave, do you?
Actually, I do microwave, but only photo chems, pop-corn and water for tea

> It's an
> Idaho special, wrapped in plastic. You just nuke & eat. I'm thinking, if
you
> nuked one of these and carefully scooped out the innards (add butter
later,
> oops, that's a cow), you might be able to turn the carcass and the plastic
> wrap into a (you-know-what-I'm-saying).

Pin-tater camera..final answer.

> I'd be happy to mail you a few these
> if they haven't made their way north of the border yet.

Sure, but send me the butter and the cow also as I am not really a vegan.

> But a whiskey tube. Come on, how much more vegetarian are you going to
get?

You got that right.

> And the answer to that question is not "beer cans"

Answer is not "beer cans" eh?.can I ask the audience?
hold it.what about a wooden beer keg?  it'd make a nice big pinhole
camera, wouldn't it?

Sorry people, the list has been so quiet that this "semi OT" message could
not possible be considered wast of bandwidth...I hope.

Guillermo

Re: [pinhole-discussion] wish me luck!

[Guillermo]

- Original Message -
From: "Stewart C. Russell" 


> I've made three cameras (out of whisky bottle tubes),

We use to have very "regular" people by eating lots of oat meal to make
Quaker pinhole cameras, cool breathed people after eating lots of Altoid
mints, people became cigar smokers to use the nice cigar wooden boxes for
pinhole and now we have drunks, were will it end?  :-)   Myself, I am a
vegetarian fan so I am waiting till broccoli comes in nice sealed
containers, is there any side efect to broccoli?  :-)

> cut and measured
> my pinholes (using a modification of Guillermo's flatbed technique),

That reminds me of the update I made to this flatbed technique page that I
have not uploaded yet.  Just did, BTW, it is nothing to write home about, it
just mentions that people owning graphic programs with measuring
capabilities, like Photoshop "Measure Tool" can measure the pinhole directly
on the screen with that digital tool.
http://members.rogers.com/penate/diameter.htm

> and made three exposures. I'm just about to develop them ...

Let us know how they turned out.

Welcome to the list.

Guillermo

Re: [pinhole-discussion] enlarging paper negatives

[Guillermo]

- Original Message -
From: "Shannon Stoney" 


> Hi, just wondered if people ever put paper negatives in the enlarger.  If
> so, are there any problems with it?

If the question were: is it doable?  my answer is yes and I have done it
once, mainly out of curiosity.  I loaded a 35mm disposable camera with a
piece of MGIV and then enlarged the resulting paper negative to 6"x6" size.
You can see the result here: http://members.rogers.com/penate/doll6x6.jpg ,
BTW, the inset negative doesn't have the same proportions of the 6x6 print.

I personal don't see a reason to enlarge paper negatives (any size)
regularly, I'd rather shoot paper the size of the intended final print and
contact print them after.

Guillermo

Re: [pinhole-discussion] Finney Pinhole

[Guillermo]

- Original Message -
From: "Christian Harkness" 


> Well, no!!!??? You should not be getting a sharp image - isn't that one
> reason for using pinhole in the first place.  If you want that with your
> 35mm camera, you best use a Nikon lens.

Interesting, opinion.

Here is mine:

"You should not be getting a soft image from a glass lens, ins't that one
reason for using a glass lens in the first place?.  If you want that, you
are best using your pinhole camera."  For some reason I think it is less
easy to accept this statement.

In my case, I make images for my consumption alone, sometimes I feel like
sharp pinhole images sometime I feel like totally defocused ones, which is
the reason I want to know what's the so called optimum pinhole, this way I
know what size to avoid when I want them defocused and  what size to target
for when I want them sharp.  Nothing wrong, IMO, with wanting relatively
sharp images from pinholes, some times.

> >It's a very cool product.  However, all the pictures are soft (not always
> >cool).

"Not always cool" :  I agree with that, sometimes is good some degree of
sharpness, altho nothing is never really sharp with pinholes.

Guillermo

Re: Re[2]: [pinhole-discussion] Zone plates & pinhole sieves

[Guillermo]

- Original Message -
From: "Colin & Linda McKie" 
>
> You don't say anything about hardware, but I guess from the quality
> and square format you're using some kind of 6 x 6. We're trying to
> decide whether to get a zone plate and pinhole sieve for our P67 with
> a bodycap mount, or butcher an old TLR (Lubitel etc?) to get a good
> viewfinder without having to fit a lens for aiming. Comments welcome
> from anyone with experience in this line.

Colin+Linda,

I have 2 Lubitels fitted with ZP (one) and Pinhole Sieve (other one), if you
mount the ZP or Sieve in th eplace of the rear glass element, you'd get a
65mm focal length, they work very nice for me.  I have a third Lubitel that
I will turn into a 65mm Pinhole camera to complement my Agfa 6X6 converted
to 35mm pinhole.  For ZP and Sieve, a shutter is almost a must (it is for me
anyway) and you can still use the shutter of the Lubitel.  I haven't used a
P67.

Guillermo

Re: [pinhole-discussion] WPPD

[Guillermo]

- Original Message -
From: "Michael Healy" 


> WWPD is under the belt! And it has been a great experience. I spent about
5
> hours lugging around the 4x5, in the heat, I should say. We had ninety
four
> degree heat today. My film turned to jelly. My brain fried like bacon.
> Listen, it's been a load of fun! So -- I hate to sound like a whiner, but.
> What do you say we do next year's in January, when the weather is bit more
> civilized?

Michael,

Remember it is a global event, it may be "civilized" in January in your
region but it would be way bellow freezing in some other regions and
probably half way to boiling temperature in many parts of the southern
hemisphere.  End of April represent a compromise, when the northern
hemisphere is in spring and the southern one is in autumn.

Guillermo (speaking for myself)
Who can't plant flowers outside in the flower bed until 3rd week of May w/o
risking them to frost!!.

[pinhole-discussion] Re: Pinhole Joys

[Guillermo]

>From the desk of Tom Miller - WPPD Team leader

> Dear All,
>
> It may be more appropriate to say "Dear Wide World."  In any case, the
> Pinhole Day clock is telling me there is only five more hours until the
big
> event.  It is almost difficult to believe that it is at hand, although
> children feel this way even more at Christmas.
>
> From my heart and and on behalf of the entire Worldwide Pinhole
Photography
> Day coordinating committee: Have a wonderful, joyous, creative and
> productive Pinhole Day.  We're all looking forward to seeing your work in
> the exhibit.
>
> Tom Miller (USA)
> And Coordinating Team Members:
>  Zernike Au (Hong Kong)
>  Jean Daubas (France)
>  Bill Erickson (USA) in memoriam
>  Guy Glorieux (Canada)
>  Gregg Kemp (USA)
>  Edward Levinson (Japan)
>  Guillermo Penate (Canada)
>  Rosanne Stutts (USA)

Re: [pinhole-discussion] Zone plates & pinhole sieves

[Guillermo]

- Original Message - 
From: 
> 
> My zone plate photos:  http://www.ellingerphoto.com/

Chris,

Wow!!  those are outstanding images.

Guillermo

Re: [pinhole-discussion] Zone plates & pinhole sieves

[Guillermo]

- Original Message -
From: "Rauch, Shelley" 


> I'm probably getting too far ahead of myself, but I've come across
> some references to these items.  Anyone have any experience with
> either of these tools?  Pros/cons/general .02 cents?

Shelley,

Here is my unbiased opinion  ;-)

Due to the "ghostly/dreamy/creamy" effect they provide, in some situations
you may find them best suited to represent what you "see".
http://members.rogers.com/penate/ZP/zone1.jpg

A pinhole is "sharp" or unsharp, a ZP or Sieve can be relatively "sharp"
while still providing a soft focus feel to the image.
http://members.rogers.com/penate/ZP/tanks.jpg
http://members.rogers.com/penate/ZP/red_green.jpg  For a given focal length,
ZPs and Sieves can be made to be much more faster than the so called
"optimum pinhole", allowing you to shoot using faster exposure times
http://members.rogers.com/penate/ZP/sg1.jpg

The above can be thought to be advantages or disadvantages, depending what
you are trying to do, It is not a matter of "pros/cons", they are just
another tools in the "lensless" arsenal.

BTW, Sieves are very new and have not been explored exhaustively, again, you
can see this as pro or con!

Guillermo

Re: [pinhole-discussion] Magnificent Obsession

[Guillermo]

- Original Message -
From: "ethereal art" 
>
> Stage 1 of this Magnificent Obsession is seeing pinhole cameras in all
> containers.

I've never been able to "overcome" Stage 1, even my wife knows it;  if I
look at a container for 2 secs or more she ask: "another pinhole camera,
eh?"....Dr. Phil, what should I do?  :-)

Guillermo

Re: [pinhole-discussion] The panopin

[Guillermo]

- Original Message -
From: "CJ Rumpolo" 


> No I fully understand it would be unfair (if not illegal) to use someone
> elses ideas without consent. I really have no plans on stealing another
> person's hard work and design. I tend to look at things I like, then try
to
> make them myself. Call it a test of my thinking skills. My current design
is
> from another person's website but have run into a snag of film transport.
>  Today I pretty much considered on giving up the whole project and just
stay
> with the camera I have.

CJ,

Don't feel bad, do not give up in your project, firstly: you are trying to
make a camera for yourself, not to massively produce it, secondly: there
aren't too many manual ways you can turn the film cartridges inside a
camera, 120 roll like cameras have been manufactured since the end of 19th
century (I think) and those patents are now expired.  If you take a look to
early 20th century rolls film cameras winding mechanism you will find
similarities with current 120 cameras mechanisms.

> I figure if I am using a 4x5 camera and I make a
> mask to give me two images of 2 x 5 on one sheet of film then I can
enlarge
> the negative to pretty much panoramic scale.

That's a good way to make panoramics, you just need a dark slide cut like
this: http://www.benderphoto.com/2x5pa.htm

> The only thing I was thinking
> about was the curved film plane. I am guessing lenses use their curvature
to
> correct for this and pinholes need the curved film plane to make the image
> appear as seen.

Regular photo lenses don't use their curvature to correct what you think.
Curved film plane pinhole cameras help you lower the light fall off.

> I tried to email Kurt from his site, hoping to purchase a camera,
>Other plans I had were to purchase an old view camera and convert it to
> a really expensive pinhole camera.

If I remember correctly, Kurt's camera was priced at around $1000 and worth
every penny, do the math, you could buy several old view cameras with the
price of one of Kurt's camera.  So don't think that buying a old view camera
and using it as pinhole camera is a bad or expensive idea.

> Then again I should use Mr. Au's camera more often as well. Its really a
> nicely made device, though I think its focal length is a bit too wide to
my
> style of photography.

Then an old view camera may be good for you, perhaps a press camera or if I
you have the money, get a 4x5 Shen-Hao http://www.shen-hao.com  it sells for
$625 at http://www.badgergraphic.com/search_product2.asp?x=2594  (a steal at
that price) and if later you want to do glass lens 4x5 you just get the
lens.

Guillermo

Re: [pinhole-discussion] Pinhole Lens... ???

[Guillermo]

- Original Message -
From: "Guy Glorieux" 

> Has anybody ever heard of this: a Minolta Pinhole Lens?
> Seems like a contradiction in terms...
>
> But it's there, on eBay!

Guy,

I think it is nothing but a regular 50mm lens to which a pinhole has been
added, probably inside the lens itself and in between the front and rear
elements, by leaving a good portion of the lens uncovered you are assured to
be able to frame the shot using the viewfinder, then you close the aperture
until it covers the round black portion on which the pinhole is made or
mounted and make the exposure.  This lens will provide enormous DOF at
expenses of diffraction.  Not a pinhole lens in the sense we use them, but a
trick many model builders (trains, ships, etc) utilize to make images of
their creations and get a DOF that is close to what they would get if the
subject was life size.

Guillermo

Re: [pinhole-discussion] Happy Easter!

[Guillermo]

- Original Message -
From: "Guy Glorieux" 
>
> May this weekend bring happiness and quiet peace to you and those around
> you.  And many beautiful pinole photographs...!

And I say amen to happiness and peace for this weekend, as for the beautiful
pinhole photos, I wouldn't mind a delay of 1 week for that wish to come true
:-)

I am going to say it the way I'd say it in Spanish:

Happy Holy week, everybody.

Guillermo

Re: [pinhole-discussion] Angle of projection

[Guillermo]

- Original Message -
From: "p g" 


> Is there a simple formula, for the mathematically challenged, to calculate
the light's angle of projection relative to the plane of an orifice as
diagramed below?
> For the Lenox's Pinhole Competition, the camera is designed with multiple
adaptors to reposition the disc to other locations using 1/2" interior
diameter PVC fittings.
> I want to calculate how far below the 0.585 mm aperture the fitting can
extend without protruding into the image's projection. Using this hardware
the fittings will need to extend 10-12 mm below the disc. Will this work, or
do I need to change the design?

P.G:

Your pinhole, if it is mounted right at the center of the fitting and if the
fitting extend 12mm bellow the pinhole, will project an unobstructed cone of
light of about 90 degrees (93.246 to be more exact).  Will it work or do you
need to change the design?   It will as long as your camera is made with a
focal length not shorter than half the diagonal of the format you are using.
If you need shorter focal length than half the diagonal of the format, just
use a fitting with a larger I.D.

For math challenged, the best is to make a scale diagram on paper.

Forgot the formulas, tell me if you really need them.

Guillermo

Re: [pinhole-discussion] going in circles

[Guillermo]

- Original Message -
From: "Marcy Merrill" 


> Here's a question for you buncha geniuses.
> With my deadline being WWPD, I have gotten off my butt and made those
> Pintoid Sours pinhole cameras I've been thinking about. After a grueling
10
> minutes, they were completed. I want to pick some brains on how I might
cut
> round pieces of film? I'm using 8x10 sheets. A scalpel around a tin didn't
> work - especially in a completely dark darkroom. Here's a page where I've
> posted some photos of what I'm trying to do and the results I've received
> thus far. www.merrillphoto.com/pintoidsours.htm
> I did all of this stuff yesterday. So far, cutting around the tin with
> scissors has worked, but it isn't perfect. Any ideas would be appreciated!
> Thanks! -MM

The following doesn't answer your question, but here is anyway:

An easier method to get round images "in camera" would be to get a square or
rectangle footprinted box (like altoids, for instance) and cut a mask in
brass or matt board with a circle in the middle.  You then need to cut
rectangula pieces of film, which is easier than cutting circles.  The film
goes first and then the mask.

Guillermo

Re: [pinhole-discussion] Determining correct aperture (wasRE: pinhole photography)

[Guillermo]

Shelley,

First, pinhole photography's technical aspects are not different from those
of glass lens photography, and that includes f/stops.  So you can get/make
pinhole apertures that would give you f/stops that "CLOSE DOWN" in the same
sequence of full stops you are use to with glass lenses, i.e., closing down
from f/16 to f/22 to f/32, f/45...,f/128, f/180, etc.  that
unfortunately would require to make pinholes to the proper sizes that would
give you the above aperture numbers.  More often than not we end up with
f/stops that aren't full stops, like f/160.

As you can see, f/160 falls between f/128 and f/180, one could make the math
calculations and find that f/160 is just about equal to f/128 +2/3 stops.
Since pinhole is not an exact practice and since pinhole exposures tend to
be more underexposed than overexposed and since for practical reason is best
to use full stops rather than fractional, the wise thing to do is to
approximate f/160 to the next smallest full stop, f/180 in this case.

Guillermo

Re: [pinhole-discussion] WWPD III

[Guillermo]

Chris has coded the frames for no scrolling, not a good idea, obviously.

There are only 6 images per artist, so if you have 1024x768 resolution, the
last thumbnail (1/2  visible in IE6) is the last image of each artist.  When
using IE, pressing "F11" key will allow you to see all of the thumbnails.

Another way to see them all is to right click on the artist names, that will
give you a scrollable page with the thumbnails, then you drag and drop the
thumbnails, one by one, into another browser window, that'll open the full
size images. It shouldn't be this difficult, tho.

BTW Chris: that's a very ingenious camera you have made, if I were not an "I
gotta made or modify the pinhole cameras I use" kind of guy, I'd have placed
an order already.   I very much like the images, especially "Mia's House",
outstanding!!.

Guillermo

- Original Message -
From: "George L Smyth" 
To: 
Sent: Monday, April 07, 2003 5:44 PM
Subject: RE: [pinhole-discussion] WWPD III


>
> For some reason I do not get a scroll bar on the right, so I am not able
to get to all of the images in the left frame.
>
> Cheers -
>
> george
>
>

Re: [pinhole-discussion] disposable camera pinholes

[Guillermo]

That dremel drill bit is defenitely a good one to use, it is bit #125 and
you can make holes of up to 1/4" with it.

BTW, the secret to convert a disposable camera to a pinhole one is: Get 2
already used disposable cameras, dissasemble one, if you have to damage it,
so be it, that's the reason for having 2 of them, once open, study how the
different parts latch with each other, this will allow you to disassembly
the other camera safely.  Then study the film advancing mechanism, this will
teach you how to reload the camera and if the new film cassette has to
suffer any modification, remove the lens, install a pinhole, reload the
camera with the film, which has to be done under darkroom conditions.

Guillermo

- Original Message -
From: "D. Hill" 
>
> You do not need a special drill bit - just one that
> isn't too big, nor too small - anything 1/8 inch and
> smaller is a good starting point.  A useful bit is
> made for a Dremel Tool and is shaped like a cone.  If
> you drill from the front, it makes a nice beveled
> edge.
>
>
> --- sherry rea  wrote:
> > will someone please share the secret of making a
> > pinhole cmaera from disposable cameras and also is
> > there a special drill bit that should be used for
> > the
> > body cap pinhole?

Re: [pinhole-discussion] bodycaps.

[Guillermo]

- Original Message -
From: 

> I was asking on friday how to make a pinhole body cap.
> I was wondering, do all the mirrors and thing in my SLR make it not work
for pinhole.

Ben,

As long as a cameras has a setting that allows the shutter function to work,
that is: lift the mirror and open up the shutter when the shutter realease
is pressed, that camera is fit fit for pinhole practice.  I assume some
cameras' shutter function may not work if a "real" lens is not installed,
cameras with electronic links between the lens a the body may require to be
set for manual exposure and/or manual focusing.

Guillermo

Re: [pinhole-discussion] 6x22 pinhole camera coverage?!

[Guillermo]

- Original Message -
From: "Tom Miller" 
To: 

> I've read a rule
> of thumb that at 30 degrees the fall of is one stop and that at 45 degrees
> it is two stops.  It seems like there is a possibly handy formula in
there.

Tom,

Forgot answering this other question.

That rule of thumb is good, but to be precise, 1 stop is at 32.76 degrees.

A formula to find the angle at which a specific fall off is found would be:

If  S = stops of fall off

Angle = ArcCosine [(1 / 2^S)^0.25]  or for better clarity:
http://members.rogers.com/gpenate/angle.gif

for 1 stops it would be:

Angle = ArcCosine [(1 / 2^1)^0.25]
Angle = ArcCosine [(1 / 2)^0.25]
Angle = ArcCosine [0.5^0.25]
Angle = ArcCosine [0.840896]
Angle = 32.76 degrees

for 2 stops it would be:

Angle = ArcCosine [(1 / 2^2)^0.25]
Angle = ArcCosine [(1 / 4)^0.25]
Angle = ArcCosine [0.25^0.25]
Angle = ArcCosine [0.70710678]
Angle = 45 degrees

Guillermo

Re: [pinhole-discussion] 6x22 pinhole camera coverage?!

[Guillermo]

- Original Message -
From: "Tom Miller" 
To: 
>
> This put two questions in head.  First, would a concave film plane reduce
> the fall off ratio?  Optimally, the film plane could be curved in a way
that
> makes the entire film plane equally distant from the pinhole.  I looked at
> the 6x22 camera's photo on the silver-whatever web site and it looked like
> it could possibly have a curved film plane, although I couldn't tell if
> would be hemisperical like the Mottweiler Pinoramic.

Disclaimer, none of the these is needed to be known to practice extreme wide
angle pinholing, but if somebody ask this questions, I am happy to oblige.

Tom,

The camera in question looks very thin, so I am pretty sure it is a flat
film plane camera.
Yes, a concave film plane would reduce the fall off ratio.  Using a film
plane conforming to a half circle and positioning the pinhole at the center
of the circle would reduce the fall off by a very substantial amount.  In
math terms, it is reduced from being cosine^4, to just cosine of the off
axis angle.  There is a catch, tho, in the case of this camera (6x22), the
focal length has to be increased to allow the width of the film to fits in
the semi-circle.

> Second, what is the formula that you used to calculate the fall off?  I'm
> curious because I've been doing a fair bit of extreme wide-angle stuff
> lately and it doesn't seem like the light falls off as much as one would
> think.

I think that we expect pinhole images to have severe fall off, therefore the
actual fall off we get doesn't look to be that severe (am I making any
sense?), it is almost magical and even seemingly defying physic laws!  but I
am pretty sure is just subjective perception.

> It is a flat film plane camera with a 1:3.7 ratio.  I've read a rule
> of thumb that at 30 degrees the fall of is one stop and that at 45 degrees
> it is two stops.  It seems like there is a possibly handy formula in
there.

There is a law in optics called Cosine^4 law, all lenses, including glass
lenses are subjected to it.  It says that the intensity of light at a off
axis point will be reduced by a factor equal to cosine to the power of four
of the off axis angle.  In your camera with ratio 1:3.7 (I'll assume this
ratio is focal length : width of format), which BTW has very similar ratio
than the one we've been discussing 60mm/22cm, the sides of the film are 61.6
degrees off axis, hence, as per Cosine^4 law, the intensity of light at the
sides will be just:

Cosine(61.6) x Cosine(61.6) x Cosine(61.6) x Cosine(61.6) = 0.051174

In other words, if at the center we have an intensity of 100 units (whatever
units), at the sides, it'll be just 5.1174 units.   To find how many stops
that correspond to, we just multiply 0.05117 by 2 as many times as needed to
reach 1 , the number of times you multiply by 2 is the number of stops of
fall off.  A faster and precise way is using this formula:

Stops of fall off = 3.322  x  Log ( 1 / 0.051174 ) = 4.29 stops

If  W = width of camera in mm  and   F = focal length of the camera in mm, a
single formula to find the fall off at the sides of the film would be:
http://members.rogers.com/gpenate/stopsW.gif

If instead we want to find the fall off at the corners of the film, when H =
height of film, the formula becomes:
http://members.rogers.com/gpenate/stopsWH.gif

Correction welcomed.

Guillermo

Re: [pinhole-discussion] 6x22 pinhole camera coverage?!

[Guillermo]

> > My inquiry is regarding how an image would look from such a
> > long neg.?  The stated aperture size is f/360. Would the edges
> > suffer from extreme distortion? I'm surprised that the coverage
> > would even fill that length of 22cm!?

The aperture is irrelevant, the only thing that matters is the ratio width
of format to focal length (corner-corner distance to focal length if one
wants to be exact). The ratio of that camera is 3.6 which in theory will
have a 4.25 stops fall off at the sides with respect to the center, this
kind of fall off is horrendous for glass photography, but for pinhole
images, in practice, it doesn't  look as big as one may think, IMO.  As an
example, this image http://members.rogers.com/gpenate/greek.jpg is a portion
of a larger image made with a camera with ratio 3 width/focal length, that
should give a fall off of 3.4 stops at the top and bottom of the image with
respect to the center, and if you ask me, it doesn't look that big of a fall
off.

> > They share no images produced with said camera so I have
> > doubts, with my limited understanding of pinhole imagery, to
> > how good the detail would be at the extremes?

Again, their camera has a 3.6 ratio, my example image has a 3 ratio, that
tells me that if the conditions are favorable: clean pinhole, thin material,
good lighting of the extremes of the scene, etc., the detail should be
acceptableand if it not, I really like the heavy fall off to the edges
effect, too.

Having said all that, I wouldn't buy or use a camera from that company,
reasons are obvious.

Guillermo

Re: [pinhole-discussion] Agfa Multicontrast Premium ASA

[Guillermo]

Marcelo Mammana pinhole-discussion@p at ???
Thu Mar 13 10:12:43 2003

>Here is my problem:
>I use Agfa Multicontrast Premium,
>The manufacturers chart, for when using the paper
>under the enlarger light, says that the paper has an
>ASA of 400p ("p" meaning paper?) when is used without
>filters, ASA160p when using contrast filters from 00
>to 3.5, and ASA80p, when using with filters from 4 up.
>Now, when I use the first camera, I get the best
>exposures when calculate them as if the paper is
>ASA64, but this is variable depending on the day
>(always measuring something close to a medium gray).
>For the second camera (a plastic 35mm film canister),
>best ASA is 125.
>In many Internet sources I've found that some people
>uses ASA 6 for paper and a very simple chart for
>reciprocity (1'', 10'' and 100'', corrected opening up
>1,2 or 3 stops), but this definitely makes grossy
>underexposed photos in my cameras.

If I understand correctly, you are saying that when you use ISO-6 you get
UNDEREXPOSED images and when you use higher rating ISO-64 or ISO-125 your
exposures are OK.  That does not make sense.

BTW, collective experience tells me the "film speed" of B&W paper is just
about 1/100 the ISO "P" of the unfiltered paper, in the case of Ilford MGIV
with ISO-P=500, its speed would be ISO-5 or the more commonly used ISO-6, so
I'd expect the "film speed" of the Agfa multicontrast premium to be ISO-4.
IF in fact it is as fast as you say it is, it'd be the best paper to use for
pinhole purposes.

>2-Can, the same paper behave different just because
>the focal lenght differs

No.

Guillermo

Re: [pinhole-discussion] Willarney's BB Idea

[Guillermo]

Hey!!, may be we can find some sponsor for this experiments: Home Depot for
the nail gun version and the NRA for the other.


- Original Message -
From: "John Moore" 

>
> Okay- NOW YOU'RE TALKING!!!
>
> I have a pnuematic nail gun... now all I need to do is figure out how to
jam the safety (this is hard with only one eye).
>
>  --- On Fri 03/14, Thom Mitchell < tjmi...@ix.netcom.com > wrote:
>
> A slingshot may also work. I know once upon a time in my misspent youth I
owned a wrist-rocket slingshot. I know I was able to put 1/4 "; 1/2" and 1"
steel shot through multiple layers of cardboard and the hole were fairly
clear. Using a bb from about 1' -2' might be the perfect combo of power to
punch through cardboard creating a nice vignette from the thickness of the
material. I would use some 16x20 paper to overcome the size of the holes.
> Pinhole-Discussion mailing list
> Pinhole-Discussion@p at ???
> unsubscribe or change your account at
> http://www.???/discussion/

Re: [pinhole-discussion] Willarney's BB Idea

[Guillermo]

>- Original Message -
>From: 
>To: 
>Sent: Thursday, March 13, 2003 6:12 PM
>Subject: [pinhole-discussion] Willarney's BB Idea


>Philip Willarney, I salute your brilliantly nutty idea! (And am not
>surprised Ms. Merrill, our associate in wierdness, came out to
>comment!).  Now, given that an airgun bb has a diameter of .175",
>we'll need Guillermo to tell us how far apart the inner sides of the
>box need to be.

Without taking my trusty slide ruler out to make the calculation, I can tell
you it would need to be like the "mother of all pinhole cameras" (or not).

Guillermo

Re: [pinhole-discussion] 120 mm zone plate

[Guillermo]

- Original Message -
From: "Daniel Bouman" 
>
> have never used a zone plate before.  I've just received a 120 mm f/80
for
> use on a field camera and I have a few questions which I hope some one
will
> enjoy answering.  It seems to me that I should set the camera's front
> standard 120mm from the film plane.

Yes,  a 120mm lens, be it Schneider, Nikon, Canon, etc. or Zone plate, is
made to focus "sharply" subjects at infinity when the lens is placed 120mm
from the film plane.

> If so, what are the near and far
> limits of the field of "sharp" focus.

Those are subjective limits with glass lenses, more so with pinhole and even
more so with ZP or pinhole sieves.  Having focal length and f/stop you can
find those limits for your subjectivity by applying the lens formulas
available in the lens faq (google find the faq)

> I've read that zone plates don't have
> the universal field of focus that pinholes have and can be focused.

Yes, that's 'cause they do focus light.

> If I
> extend the bellows for a close in shot then I'm not using the zone plate
at
> the focal length it was designed for, right?

If you extend the bellows and your subject is not at infinity, you are not
using the lens at the focal length it was designed for, and it doesn't
matter if it is zoneplate or your expensive Rodenstock lens.  When you
extend the bellows, you are increasing the "effective" focal length of the
lens, therefore you have to reduce the distance lens to subject, they have a
reciprocal relationship, you increase one you'll have to decrease the other.
In short, it is OK to use the ZP for a distance lens to film longer than
120mm, provided your subject is closer to the camera.  Again, refer to the
lens faq to find out how much you should extend the bellows for a particular
distance lens to film.  Having said that, I wouldn't worry too much, I mount
my
zoneplates at the "calculated" distance and use them like that no matter
where the subject of my picture is.

> Or is it that the depth of
> field at f/80 is big enough to cover a subject at a foot or two from the
> camera?  Any takers?  Cheers, Daniel Bouman

In practical and for "lensless" imaging purposes the answer is yes.  In
mathematical terms, you would have to extend the bellows beyond the focal
length distance the lens was calculated for.

For instance:  for your 120mm ZP and a subject at 2 feet (609.6mm) from the
lens, the bellows should be extended

F=focal length the ZP was calculated for
S=distance lens to subject
I=bellows extension

I = (S x F) /  (S - F)
I = (609.6 x 120) / (609.6 - 120)

I = 149.4mm

Hope it helps,

Guillermo

Re: [pinhole-discussion] Howdy

[Guillermo]

- Original Message -
From: "Colleen Newquist/Michael Weiss" 
>
> Now the question. I'm starting to build my third pinhole camera an would
> like build a mechanical
> shutter that could be used with a cable release. Does anyone know of
> plans on the web or in publication? Thanks.

Take a look at this page, it has 2 or so images that may give you a very
good idea of what you want to achieve:
http://www.cyberbeach.net/~dbardell/pinhole.html

Guillermo

Re: [pinhole-discussion] F-stop question

[Guillermo]

Jason,

If what you need to know is how many stop there are between f/138 and f/176,
the answer is 0.7 stops. Having said that, you don't need to do any exposure
compensation.  If your 4x5 camera with 50mm has an aperture of f/138, it
really doesn't matter what the "appropriate f/stop for 50mm" is, the only
importante thing is the actual aperture of the camera, f/138 in your case.

BTW, if f/138 is "perfect" for 25mm, that would mean f/195 to be "perfect"
for 50mm, not f/176.

Calculation upon request.

Guillermo


- Original Message -
From: Jason Edleman
To: pinhole-discussion@p at ???

All,
I have a 50mm 4x5 pinhole camera with an f-stop of f/138 (perfect for focal
length of 25mm).  The appropriate f/stop for 50mm is f/176.  Does anyone
have a calculation for figuring out the exposure compensation?
Thanks in advance -
Jason
:...:
Jason
:...:

Re: [pinhole-discussion] resolution vs diffraction vs format question

[Guillermo]

- Original Message -
From: "Uptown Gallery" 
To: 
>
> Does anyone (Guillermo?) have this figured out?

Murray,

Richard gave you a good answer.

If I may add an example: Assuming and 8x10 final print from a 4x5  50mm
pinhole camera with an optimal pinhole size
0.259mm in diameter.  When you enlarge the 4x5 to 8x10, each "image point"
will become double in size.  If we say each image point is equal to the
diameter of the pinhole, they'd become 0.259 x 2 = 0.518mm in size.  If
instead you make an 8x10 camera 100mm focal length (to keep the same
perspective), this camera would require a pinhole diameter of just 0.366mm
which is much smaller and therefore would look sharper than the 0.518mm
image points obtained from our 4x5 camera.

BTW, the so called optimal pinholes sizes used above are product of the
formula I use, nevertheless, comparative results would be the same using
whatever of the many existing formulas to find pinhole sizes.

Guillermo

Re: [pinhole-discussion] freestyle cold-stored color film $ blowout

[Guillermo]

- Original Message -
From: "George" 
>
> Did they include a URL?  I didn't see anything on their site (I think I
was looking at their site).

http://www.freestylephoto.biz/clearance.php?wcat=99

Guillermo

Re: [pinhole-discussion] New find for paper negatives...

[Guillermo]

- Original Message -
From: "Michael Healy" 


> I imagine half a case of Home Depot toilet paper.
>
> Ow yes... Don't get Linagraph Direct paper... (Cat 198 6520) ... it
doesn't
> appear to be sensitive to White light at all...man do I have a bunch
too...
> it comes in 12"x400' rolls.

No comments..needed ;-)

Re: [pinhole-discussion] Re: Developing paper negatives

[Guillermo]

- Original Message -
From: "HypoBob" 
>
> As for exposure time, my f/360 camera with Ilford MGIV and a yellow filter
needs about 8 to 10 minutes in full sun.  On sunless days I do not use a
filter, but the lower light levels still demand about the same exposure
time, if not more.

MGIV behaves as ISO-3 for you, then.

According to "sunny16" rule, under sunny skies your exposure should be f/16
@ 1/3 seconds.  There are 9 full stops between f/16 and f/360, therefore
f/16 @ 1/3 seconds becomes f/360 @ 170 seconds.  A K8 filter has a factor of
2, that makes the exposure f/360 @ 340 seconds, reciprocity correction
factor would be around 1.5 (as per reciprocity correction table in my small
article http://members.rogers.com/penate/pinsize.htm ), that makes the
exposure f/360 @  510 seconds or  f/360 @ 8 minutes 30 seconds.

Guillermo

Re: [pinhole-discussion] Tin can hole punch

[Guillermo]

- Original Message -
From: "Guillermo" 

BTW, you don't need a hole 1/2" in diameter, 1/8" to 3/16" is more than
enough.  The smaller the hole the easier it is to drill it w/o tearing the
tin.  A dremel drill with a conical bit (#125) is perfect to do this.

Guillermo

Re: [pinhole-discussion] Tin can hole punch

[Guillermo]

- Original Message -
From: "Michael Heath" 

> I'm in the midst of making a camera out of a tea tin.  Is there an easy
way
> to punch a 1/2 inch hole in the tin where I can place the pinhole?  Or do
I
> have to break out the saw and cut an irregular shape?  I was wondering if
a
> heavy duty hole punch, or something similar, would do the trick.

Drill it.

Guillermo

Re: [pinhole-discussion] Resistance is futile...

[Guillermo]

- Original Message -
From: "Guy Glorieux" 

> In French, gender is identified immediately with the person:  e.g. "the"
> teacher is either "le" or "la" professeur.  Then "his" or "her" students
> are gender neutral as "ses" étudiants (unless, of course there was only
> one student, in which case the student's gender would be clearly
> identified in it's own right as "son étudiant" or "son étudiante" while
> the possessive would still remain gender neutral as "son").

Spanish as another of the romance languages, follows the same pattern: "el
profesor" or "la profesor" and "sus estudiantes"

> Now in English, things go exactly in the opposite:

Which makes it difficult to for new speakers"

"I drive on the parkway and park on the driveway"
"I seed a fruit to remove its seeds"
"an alarm goes OFF when its electric circuit goes ON"

And to keep it in topic:

"I call them pinholes but I actually make them with needles"  :)

Guillermo

Re: [pinhole-discussion] Coverage

[Guillermo]

- Original Message -
From: "Michael Healy" 
>
> By this logic, my 7x17 camera will require a focal length -- a bellows
> length, technically -- that exceeds the film diagonal of 18.4" divided by
> 3.5, or approximatley 4.85". In other words, if I build this camera with a
> body length of 6 inches, then I ought to receive adequate coverage on a
> 7x17" sheet of film.
>
> That's my logic. But is it sound? Are there other factors I have not
> accounted for?

Mike,

Reasoning is sound, all the factors are included in that 3.5X factor (for
flat film planes) you mentioned.  The factor, BTW, depends on whatever you
can live with, a pinhole would project a circular image and it is up to the
photographer to decide what level of fall-off is acceptable, Renner likes
3.5X, someothers may like 2X and sometimes even 5X.  Since you already
experimented with a 50mm focal length on a 4x5 format, which gives you a
"factor" of  3.25X and find that OK, then using 3.25X or smaller factor
would assure you equal or better coverage in your 7x17".

About the only flaw I found, well actually we should blame the calculator
not you, is the fact that 18.4" divided by 3.5 is not 4.85"  :-)

BTW, the angle of view of your camera, assuming 6" focal length, will
be -about- equivalent to the angle of view you'd get with a 14mm lens on
your 35mm SLR.  You'd have to sell your first born and mortgage your house
to buy such lens for a 7x17", if it existed.  That's another reason I love
pinhole!

Guillermo

Re: [pinhole-discussion] camera conversion question

[Guillermo]

Murray,

I hope I understood your description (sometimes my ESL comprehension fails
me miserably).

You are considering (first) the 4" side of the bellows frame opening: Since
the bellows do not end at the center of the lens (or pinhole for than
matter) but beside the shutter, the angle between them and a perpendicular
to either side of the 4" opening is irrelevant, the bellows will not
vignette your image unless they sag beyond a line from the end sides of the
4" opening and the pinhole.  If the aim is to get a 4x5"  image by building
an extension box, you should analyze the 3" size first, as the ratio 4"
intended image size to 3" opening is greater than 5" image side to 4"
opening.  If you lower a perpendicular from the pinhole to the film plane,
you'll have a triangle (let's call it "A") with corners at: "pinhole -
middle of the 3" opening - end side of the 3" opening", you also have
another triangle (let's call it "B") with corners at: "pinhole - middle of
the 4" image size - end side of the 4" image size",  since this 2 triangles
have equal angles, we can write that:

Base of "A" divided by Base of "B"  =  height of "A"  divided by height of
"B"

Base of "A" is half the 3" opening = 1.5" =  38.1mm
Base of "B" is half the image size width of 4" = 2" =  50.8mm
height of "A" = bellows extension = 130mm
height of "B" = height of "A" +  extension box deepness EBD = 130 + EBD

So you have:

Base of "A" / Base of "B"  =  height of "A" / height of "B"

38.1 / 50.8  =  130 / (130 + EBD)

EBD = (130 * 50.8 / 38.1) - 130

EBD = 43.33mm

An extension box of 43.33mm will give you an image width of just 4",  since
my skills and tools to make cameras or modifications to existing ones aren't
that great, I'd make it at least 46mm deep instead.

A similar analysis can be made for the other side and the result would be
1.28" (close to your finding of 1.25"), but since it this result is smaller,
you have to use the larger one of 43.33mm, which is equal to just above 1.7"

All the above could have been explained fast and nice with a simple drawing,
but this is just an ascii posts only list.

Guillermo





- Original Message -
From: "Uptown Gallery" 
>
> Gutted some Polaroid rollfilm cameras with 130 mm lens/bellows. Extends a
> little farther than that due to 3.5 feet to infinity focus adjustment.
>
> Pulled lens, kept shutter for experimentation on one.
>
> Rear opening of bellows frame is a hair larger that 4" x 3". I took some
> measurements along 4" axis and calculated a 22 degree angle for the
bellows.
> From this I figured I need a 1.25" entension box to get a 5" image. I
didn't
> calculate or measure the short side yet...might be different due to aspect
> ratio of 4:3 differing from 5:4.
>
> Gonna try ground acrylic instead of glass.
>
> Question is, with a pinhole I should have adequate coverage, but do you
> think my anticipation of angle will prevent 'vignetting' by the bellows or
> rear of the camera (existing opening?)
>
> Thanks
>
> Murray
>
>
> ___
> Post to the list as PLAIN TEXT only - no HTML
> Pinhole-Discussion mailing list
> Pinhole-Discussion@p at ???
> unsubscribe or change your account at
> http://www.???/discussion/

Re: [pinhole-discussion] Guillermo's 5 lp/mm optimum design

[Guillermo]

- Original Message -
From: "HypoBob" 

> Guillermo,
>
> In a posting on 13 December you stated that an 8x10 pinhole image rivaling
the resolution of a lens image (i.e., 5 lp/mm) could be obtained with a
> focal length of 120 mm or less and the optimum pinhole.

> Since one could place any size negative material in such an arrangement,
aren't you in effect saying that a 120 mm focal length is the maximum for
> obtaining 5 lp/mm resolution?

Yes, but those 5 lp/mm are on the film which is more often than not and
intermediate step to the final result, the latter being, more often that
not,  a positive print.  So although the resolution you may have on your
35mm format made with the optimum size pinhole 50mm body cap is better than
5 lp/mm when you enlarge it to 8x10 you will get a print with just about 1/8
the resolution on film. If you didn't have to enlarge and view the print at
the "normal distance of comfortable vision", then, the 5 lp/mm are enough.
Now, if you make a 16x20 pinhole camera and view that print at a distance
equal to twice the "normal distance of comfortable vision", you will then
only need 2.5 lp/mm on the print, in which case 480mm focal length would be
the maximum.

> Is there also a minimum focal length for this resolution?

Not mathematically, but practically there is.  For a given format, there is
a minimum limit of the focal length that would "acceptably" cover the film
format, as well as there are practical limits forced by how small a camera
we can make, a manufacturer of laser drilled pinholes once sent me a 0.001"
pinhole good for an "optimal" focal length of under 0.5mm!!  I couldn't
possible make a camera with such focal length.

> Do you have some equations you can share with us that give the
relationship between resolution, focal distance, and pinhole size?  I'm
guessing
> that this all may be based on the usual equations with a properly chosen
value for the circle of confusion.

Resolution = 1 / (1.22 * wavelength * fstop)

if you use wavelength = 0.00055mm, it becomes:

Resolution = 1490 / fstop

Assuming you know the resolution and want to know what fstop would give you
that resolution:

fstop = 1490 / resolution

but, fstop is also equal to:

fstop = Focal length / pinhole diameter

and:

pinhole diameter = 0.03679 * SQRT(Focal length) {units in mm}

therefore:

fstop = Focal length / (0.03679 * SQRT(Focal length)

or also written as:

fstop = 27.1813 * SQRT(Focal length)

therefore:

Focal length = ( fstop / 27.1813 )^2

How did I get 120mm as the maximum focal length I talked in my post?:

I started with the need of 5 lp/mm, therefore:

fstop = 1490 / resolution
fstop = 1490 / 5
fstop = 298

Focal length = ( fstop / 27.1813 )^2
Focal length = ( 298 / 27.1813 )^2
Focal length = 120mm   (aprox)

> In any event, it seems that the conditions will hold only 'near' the
center of the image because the corners and edges are beyond the optimum
focal
> distance.

That is true, but you could have a semicircular film plane with the pinhole
in the center of the semicircle, in which case the distance pinhole film
would be constant (in one axis, at least).  Make the film plane half an
sphere and you will get same distance everywhere on the film plane  :-)

>Also, I'm thinking that you may be assuming a certain viewing distance for
the observer since smaller images tend to be held closer to
> the eye than do larger ones.  That is, the 8x10 size may be necessary to
get the viewer to hold the 5 lp/mm print about 20 inches from his eyes
> rather than the 12 inches at which he may hold a smaller 5 lp/mm print.

That is correct.

> Thanks for getting me off onto this tangent.  I always enjoy your posts,

Thanks, I enjoy posting them, it keeps my brain from getting rustier.

BTW, corrections to the above are welcome.

Guillermo

Re: [pinhole-discussion] #80 drill bit

[Guillermo]

- Original Message -
From: "Traci Bunkers" 

> I also have a dremel with a flexshaft. I wondered about it, but thought it
> would pose the same issues as the drill.
>
> I thought about layering a bunch of pieces from aluminum cans and drilling
> through them all at once. Has anyone tried this? I guess there's only one
> way to find out if it will work!

Unless you have a way to clamp/compress securely all the layers, the drill
bit would likely brake.  What you need is a drill press like this one:
http://www.dremel.com/html/products/toolsacc_fr.html , I got one and
although I don't use it to make my pinholes, I have used it and works
beautifully for that purpose.

Guillermo

Re: [pinhole-discussion] The next Epson scanner after the 2450?

[Guillermo]

- Original Message -
From: "Richard Heather" 
To: 
Sent: Saturday, January 04, 2003 1:34 AM
Subject: Re: [pinhole-discussion] The next Epson scanner after the 2450?


> I have a 2450. The resolution at 2800 gets grain with most films. Unless
you
> shoot TechPan or Kodachrome 25 I doubt more rez will improve the image.
> Somehow TriX 5x7 (inches!) seems grainier than 35mm.
> Richard Heather

That actually is good, "the grainier the film looks" the better the scan is
(if that grain is the actual grain of the negative). Higher resolutions are
not used to "improve" the image but to capture the image the way it actually
is.  BTW, you also see the film grainier if you see it with a enlarger
focuser, it is the same thing.  Remember that when you scan at a resolution
of 2450 DPI, your monitor, assuming the resolution is 1024x768, can only
display a rectangle 0.3 by 0.4 inches of the total area of the film,   it is
the equivalent of enlarging your 5x7 to 80x114 inches size.

Guillermo

Re: [pinhole-discussion] Season's greetings to all!

[Guillermo]

- Original Message -
From: "Mike Vande Bunt" 


> Well said!  (You don't have to pay royalties to Mel Torme for the use of
> that line, do you?)  ;-)

What do you mean, Mike?

Last nite I was roasting some chestnuts on an open fire, when suddenly came
to me the fact that people try to say Merry Christmas in so many different
ways these days, some trying to be inclusive, some trying not to offend
others, some trying to offend others and  some trying to be just politically
correct.   In my city's City Hall, what always was known as a Christmas
tree, now it is called Holiday tree!.  Anyway, as I said, I was roasting
these chestnuts on an open fire, when the line just came to me!!  in part
for the above in part 'cause I thought I could used the shell of a chestnut
to make a pinhole camera.  :-)

Guillermo

Re: [pinhole-discussion] Season's greetings to all!

[Guillermo]

Though its been said many times, many ways Merry Christmas to (all of) you!

Guillermo

Re: [pinhole-discussion] Message from a non member

[Guillermo]

- Original Message -
From: "James Kellar" 

> I will be on sabbatical for several months, away from this email
> box.  Please mail submissions to Professor Tom Morrissey, PO Box 321,
> Lincoln, RI 02865.  If you want your materials returned a SASE is a
> must.

Well Professor Morrissey, you know what they say: "If it sounds too good to
be true, it probably is"?  The problem with your request is that it makes no
sound at all!!   So, here is my suggestion:  enjoy your sabbatical and when
you get back and are reachable  by other more real time means not just by
SNAIL mail to a PO.Box, send your request back to us with REAL and
MEANINGFUL details/information, then we (I, anyway) may consider it. In the
mean time,  Merry Christmas to you, too.

Guillermo

Re: [pinhole-discussion] more Sieve images

[Guillermo]

http://members.rogers.com/penate/sieve/comparison.html

Guillermo

Re: [pinhole-discussion] Pinhole Focus

[Guillermo]

- Original Message -
From: "Ian McKee" 


> I made two assertions; 1) that at a given extension you will get the same
> image regardless of pinhole size and 2) that the sharpness was the same
for
> each image.
> I will stuck to the first and admit I'm on shakier ground on the second.

You are absolutely right on the first assertion, for a given extension, no
matter the size of the aperture the resulting perspective is the same. The
same happens when mounting an SLR with a non-zoom lens on a tripod and
taking several exposures each one with a different aperture without moving
the camera or tripod, all images will be the same, all images will have the
same perspective.

> Regardless of the results, doing it is fun and enlightening!

That's the most important thing, good for you!

Next time you do the test, I suggest your subject is closer to the camera,
or maybe even have a near object and a far one and a subject in between.
You can go as close as 10 or 15 times the focal length distance if you
wanted, for the near object.  Let us know the results.

Merry Xmas to all.

Guillermo

Re: [pinhole-discussion] Yet another lensless technique !!

[Guillermo]

- Original Message -
From: "George L Smyth" 
>
> I like that very much.  Now it's a matter of either figuring out the
specifics
> of how to make one and/or waiting for someone to offer them commercially.

George,

Since I am offering zone plates already, I will add Photon Sieves and
Pinhole Sieves to the offering, wait for an announcement on this.

Guillermo

[pinhole-discussion] Yet another lensless technique !!

[Guillermo]

I just finished writing and web-publishing a small article about the newest
lensless technique.  Similar to zone plate, it used diffraction in order to
focus light, but instead of rings, it uses a large amount of pinholes
appropriately distributed, this technique is called PHOTON SIEVE imaging, I
invite you to take a look at:

http://members.rogers.com/penate/sieve/photonsieve.html

Guillermo

Re: [pinhole-discussion] Pinhole Focus

[Guillermo]

- Original Message -
From: "Ian McKee" 
>
> Hi !
> I'm Ian McKee and I've been following the discussion on focus of pinhole
> images and I think some of you are getting more complicated than
necessary.

I think you are mistaken, no one is getting or trying to get complicated in
the actual practice of pinhole imaging, all the thread was to answer Lisa's
inquiry about what diffraction was.  We all know any hole would produce an
image.  I actually have made demonstrations to show workshop participants
that pinhole is not an "esoteric" or difficult practice.  I just take a
nail, litterally stab a cardboard board with the nail and w/o cleaning the
hole make a pinhole image.   Some of us just need sometimes to understand
what is happening and why is happening.  Some others are just interested in
the results alone.  Nothing wrong with any ot the 2 groups, IMO.

> Calumet sells a set of twelve pinholes ranging from .0059" to .032". I
have
> mounted these on a 4" x 5" camera and shot the whole series at an
> arbitrarily selected bellows extension=focal length of 210 mm. With each
> pinhole I get the same image and the same degree of sharpness.
> rest of message was snipped

I could explain you that what you have observed, contradicts proven laws of
physic, and that if you are correct, there is a nobel prize winner that
literaly wasted 10 years of his life studying pinholes and related matters,
all in vain.

Guillermo
(who likes the science surrounding pinhole, but leave it home when he goes
out to make images)

Re: [pinhole-discussion] Polaroid pinhole

[Guillermo]

- Original Message -
From: 


> Hello
> Thanks for the responses, If I make a pinhole camera out of an old
polaroid will it still develop the pictures in camera?

Yes and no!   AFAIK, polaroid pictures are not developed in camera but
outside of it, having said that, some cameras eject the image automatically
after pressing the shutter and some need the photographer to pull a paper
tab.  If you modify a camera that auto ejects the image in such a way that
damage the electronics, the eject mechanism may no longer work. In that
sense, it'd be easier to modify a camera that uses film that needs to be
pulled out manually or build a camera around a polaroid holder, 405 for
instance.

Guillermo

Re: [pinhole-discussion] What is Diffraction?

[Guillermo]

- Original Message -
From: "Guillermo" 




> As we all know pinhole is not about sharpness, nor I am suggesting we
strive
> for it.  Having said that, it is actually possible to make poinhole images
> that under certain conditions could be undistinguishable from glass lens
> images. A good example is an image in the Renner's pinhole book.  Under
the
> assumption that we humans can discern more than 5 line pairs per
millimeter,

The last statement should have read: "Under the assumption that we humans
CAN NOT discern more than 5 line pairs per millimeter with the unaided eye"

Guillermo

Re: [pinhole-discussion] What is Diffraction?

[Guillermo]

- Original Message -
From: "Lisa Reddig" 

I thought I had commented on this Lisa's post, but I guess I didn't, here is
my admitely late comment:

> So what everyone is basically saying is that the reason my pinhole images
> are not precisely sharp is because it is in actuality impossible.  Even
with
> all the equations and formulas.  Correct?

As we all know pinhole is not about sharpness, nor I am suggesting we strive
for it.  Having said that, it is actually possible to make poinhole images
that under certain conditions could be undistinguishable from glass lens
images. A good example is an image in the Renner's pinhole book.  Under the
assumption that we humans can discern more than 5 line pairs per millimeter,
most of the 35mm format lenses (especially the Zoom variety) would be hard
pressed to produce enough resolution on film to give those 5 lp/mm when
enlarged 8 times for a print about 8x10" in size. The same 5 lp/mm could be
achieved if you make an 8x10" pinhole camera with a 120mm focal length or
under, using the so called optimum pinhole size.  Print should be viewed
with unaided eyes.

Guillermo

Re: [pinhole-discussion] polaroid pinhole.

[Guillermo]

- Original Message -
From: 


> Dear All
> I was wondering if could help me.
> I want to do polaroid transfers, and want to know if anyone knows a cheap
an effective way to make a polaroid pinhole camera that can do this.

Ben,
The easiest and cheapest would be to get yourself either a Polaroid
holder or camera that takes the film you want to use and then you build a
wooden box around the holder and or modify the camera to make it a pinhole
camera.  There are always holders and cameras being auctioned at eBay that
can serve the purposes mentioned, these are some currently being auctioned:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1944584085
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1944512695

The main thing is to make sure the holder or camera actually takes the film
you intend to use, as there are older Polaroid holder/cameras that may seem
to take modern film but they will not, so do your homework before bidding.

I bought an oscilloscope camera at eBay, from that purchase I have a shutter
like this http://tonopahpictures.0catch.com/G-Claron/Ilex75_4.jpg that I
could use for pinhole , a close up lens I use as paper weight and a holder
exactly like this one: http://tonopahpictures.0catch.com/021502/pinhole0.jpg
http://tonopahpictures.0catch.com/021502/pinhole2.jpg that I also converted
to pinhole camera.

Disclaimer: those auctions above are just to give you an idea, I do not know
the persons auctioning that stuff nor I have any interest in them selling
it.

Guillermo

Re: [pinhole-discussion] What is Diffraction?

[Guillermo]

- Original Message -
From: 
To: 
Sent: Wednesday, December 11, 2002 9:27 PM
Subject: Re: [pinhole-discussion] What is Diffraction?


> Here's a question that has troubled me for a long time, since we've gained
> the attention of the physicists among us. If the optimal image occurs when
> all light waves are 'in phase", which the Young article says occurs at the
> junction between the nearfield and farfield diffraction patterns (whatever
> that is), is there another point further on where the various waves again
> come into simultaneous phase sync, and thus optimal sharpness?
Theoretically
> there should be, but how far?

Physicists analyze diffraction using either near or far field methods.
Far-field means the source of light is far relative to the aperture size,
the wave front arriving at the aperture is assumed to be flat.  Near-field
is the apposite, wave front is assumed to arrive curve shaped.  This, I
believe, also affects or determines how far from the aperture the near-field
diffraction reaches and how far from the aperture the far field diffraction
starts.  There is a gray area in between, this area can be assumed to
separate near and far field diffractions voiding any "juncture" of them, and
as Young's article says: "here, the image is not amenable to description by
simple arguments".   When you talk about "in phase" you may be thinking
about how a zoneplate works, where the aim is carefully position the edges
of the clear rings so the diffractions caused by all of those edges
positively interfere at the focal point and therefore add up their
intensity. Pinhole does not work like that.

For my view of how zoneplates work, pls read:
http://members.rogers.com/penate/zoneplate.html
It talks a bit about the near and far field diffraction, also.

Don't quote me on all this pls, this is just a layman's view of the topic.

Guillermo

Re: [pinhole-discussion] What is Diffraction?

[Guillermo]

- Original Message -
From: "Lisa Reddig" 
>
> I've been hunting on the web for a good description of diffraction, but it
> all talks about physics and x-rays.  Could some one give a real simple,
> basic description of diffraction and how it shows itself in pinholes?  I
> would appreciate no equations if possible.  An example with a picture
would
> be cool.

You already got answers to your question, so I'll try to be as terse as
possible:

Diffraction is the bending light suffers when it "skims" an opaque object.
This java applet shows you exactly that:
http://micro.magnet.fsu.edu/primer/java/diffraction/index.html
By selecting (with the slider) different colors you can see how they are
diffracted.  Red diffracts more than violet.  Green/yellow in the middle of
the slider (550nm) is what represents the average of all colors, that's why
people using formulas to find the optimum pinhole size use that color
wavelength in their formulas.
By moving the size of the aperture you can see that the smaller the aperture
the more diffraction it causes.

In a perfect world, the image a pinhole would produce of a point source of
light would be a perfect dot the size of the pinhole, but because
diffraction, the image of that point source of light is a dot of light
surrounded by alternate dark and light concentric rings, very much like what
you see here:
http://www.microscopy.fsu.edu/primer/java/microscopy/airydiscs2/
BTW, the white rings represent the dark rings.

So we where expecting a dot of light and we have a "bulls eye" like dot
instead, as you can imaging this causes the image to be unsharp.

As for showing you a sample, it'd be very difficult with a pinhole image.
Fortunately, light doesn't care if you are using a pinhole or an expensive
lens, diffraction is always there.  So I'd suggest you do the comparison
yourself, take your SLR, an take an image using the widest aperture your
lens have, then place a pinhole in front of your glass lens and take an
image, compare the images, any difference you see will be due to the
diffraction smaller aperture is causing.

Guillermo

Re: [pinhole-discussion] I am so not done wondering!!!!

[Guillermo]

Ok, I get it, digital stuff is just another way of doing it,as for the
real question:  Is it art?

Just kidding people, just kidding   :-)

Re: [pinhole-discussion] wondering

[Guillermo]

- Original Message -
From: "Dan Gerber" 
>
> Seriously, I spent almost every waking hour of my 4 years of college in
the
> darkroom, and yet now, when I own a home with a lovely space for a
darkroom,
> and all of the equipment I need(x2!) I don't have a darkroom! Why? Because
I
> don't need one for the type of work I do, and my highly experimental
nature
> has led me to digital processes(it also doesn't help that I work for
Adobe!)

They offered me a job, but when I read the contract, the line where it says:
"Thou shall not do it in the dark", I declined to sign.  :-)

Re: [pinhole-discussion] New Camera from Joaquin Casado and prompt box

[Guillermo]

- Original Message -
From: "George L Smyth" 


> Hmmm, okay.  Very poor website design.  I would like to see more pictures,
get
> more details, maybe even find out how much it costs.  I have no desire to
send
> him an email.  Anyway, I do my email through Yahoo, so this doesn't do me
a
> whole lot of good.  Too bad that something that should be so simple
becomes
> impossible.  I wonder if the camera is similarly designed.

Common George, give Joaquin a break.  The 1000's words the pictures in his
site say speak very loud of his design and  craftmanship.

I said in my post that this was a PRE-ANNOUCEMENT.   Joaquin sent me and  a
couple of other persons an email for us to PRE-VIEW his new creation, the
site IS NOT meant as THE site from which he'll sell this camera, nor it is
intended to ANNOUNCE the camera to the world, it says in the home page that
there will be a web site coming soon.

I'll stop short of saying I made a mistake with my posting of Joaquin
pre-announcement to the list, Joaquin indicated to me, he was surpriced to
find this morning so many emails from people interested, so no question some
people were impressed with the beauty of the cameras and wanted to know
more.

Guillermo

Re: [pinhole-discussion] New Camera from Joaquin Casado

[Guillermo]

- Original Message -
From: "George L Smyth" 
>
> It does look pretty cool, though I wonder about the cost.  I clicked the
link
> for more information, but got a Prompt box that then got rather confused.
Oh
> well.  Usability is the most important thing on Web page.

My mistake, I should have pointed to the "HOME" page instead, in it Joaquin
mentions: "This is just an exerpt from
our new Website,which will be published soon".

About the cost, I wonder about that myself, I am pretty sure it'd be an as
handsome sum as the cameras themselves.

Guillermo

[pinhole-discussion] New Camera from Joaquin Casado

[Guillermo]

Joaquin Casado, maker of the handsome 4x5 Hal Camera has know pre-announced
the beautiful Curva120, as the name implies, it is a curved film plane
taking 120 film.  Incredible design.  Take a look:

http://usuarios.lycos.es/jsendec/curva_english.htm

Guillermo

[pinhole-discussion] Custom made Zone Plates

[Guillermo]

People,

Besides Pinhole and Slit photography, there is another of the so called
lensless techniques, that is: Zone Plate imaging, not quite popular because
making a Zone Plate lens is not as easy as making pinholes, and the zone
plates available (http://www.pinholeresource.com/products.html#zoneplates)
have focal length that may not match the cameras we are making or modifying.

If you are interested in giving Zone Plate a try, this shameless
announcement may be for you:

http://members.rogers.com/penate/customZP/customZP.html

Thanks,

Guillermo

Re: [pinhole-discussion] uploaded photo with "thing" in corner

[Guillermo]

- Original Message -
From: "Traci Bunkers" 


> I never thought about it being a light leak. Being that it is roundinsh,
any
> idea where it might be coming from?

Try the first link on this page:

http://www.theverb.com/holga/camera_links.htm

Re: [pinhole-discussion] uploaded photo with "thing" in corner

[Guillermo]

- Original Message - 
From: "Jeff Dilcher" 
> 
> Looks like a light leak.  I think Holga owners considers that a "feature"
> and not a problem!  There is a reason these cameras were (originally)
> inexpensive...

Some Holga aficionados would kill for a Holga with that "problem".

Re: [pinhole-discussion] ballpark pinhole exposures for a gift pinhole camera?

[Guillermo]

- Original Message -
From: "Philip willarney" 

snip
>the focal length is about 40 mm, and I
> haven't figured out an exact f-stop for the pinholes
> yet).
>
> Use ASA 100 film
> Bright sun: 2-4 seconds

Philip,

Usually it is the other way around, you figure out the times based on your
aperture, and you find the aperture either by: 1-shooting and taking notes
until you "know" your camera and based on that find the aperture, or 2-by
measuring the pinhole diameter
http://members.rogers.com/penate/diameter.htm

In any case, based on your Bright sun exposure of 2 - 4 secs, the camera(s)
should have an aperture of around f/180, that, in turn, dictates a pinhole
size very close to the so called "optimum size".

If I were you, I'd measure the pinholes, find the f/stop and then come up
with the exposure table. I find that the easiest way to maintain or creating
enthusiasm for something is by having success from the start and a good
exposures table is surely a way to help your relatives to succeed from the
beginning.

Guillermo

Re: [pinhole-discussion] [pinhole-dicussion] reciprocal failure

[Guillermo]

- Original Message -
From: "karol" 

> i've got an Zero Image pinhole camera
> and i've got a question concerning sth called 'reciprocal failure'.
> In a instruction added to a camera it's written
> that it means that i need to multiply the speed by 2 when it's 1-2seconds,
> by 4 when it's 2-4...by 12 when it's more then 10 or sth like this. anyway
> it's written in a very simplified way so i'd like to know some details.
the
> aperture in this camera is 138.

Karl,
 Exposure is given by a pair of parameter, they are: Time and
Aperture, there is a reciprocal relationship between them.  That means that
if you increase one of the values by a factor X and decrease the other by
the same factor X, the exposure will be the same.   An example: 20 times 40
is equal to 800, but if you halve 20 and double 40, their product will also
give you the same result  10 times 80 equal 800.   Another example: f/60 @
1/200 secs = f/90 @ 1/100 secs.

Unfortunately, when your exposure time gets (usually)  bellow 1 sec or
higher than (usually) 1/1000 sec, that reciprocity between Time and Aperture
fails, hence Reciprocity Failure.  The effect is that you will need to
expose for longer than what the reciprocal relationship is telling you.
Each film has its own characteristics, therefore, each film FAILS in a
different way.

Guillermo

[pinhole-discussion] way OT

[Guillermo]

Could someone possible help me to identify which city and perhaps area of
the city this image was taken at?

http://www.kamado.com/images/Balcany_Pictures/balc1.jpg

Sorry about the OT.

Guillermo

Re: [pinhole-discussion] RE: pinhole size

[Guillermo]

- Original Message -
From: "Paul Prober" 

The problem experimenting with different pinhole sizes is that unless we are
making exposures of resolution targets
http://www.???/resources/articles/Young/images/fig5.jpg the
results will be always subjective to each viewer, scene, image contrast,
whether subject is at close or far from the camera, angle of view, etc,
and/or a combination of the above.

>  I have not experimented to find the optimum pinhole size.  Chris Patton
> has, and his conclusion was that the Prober-Wellman Formula is a practical
> values to use for f/stop to pinhole size for reasonable Circles of
> Confusion.
>  See http://www.stanford.edu/~cpatton/phcalc3.htm  which uses the
> Prober-Wellman Formula.

Patton actually uses a different formula or maybe I should say different
"constant" as all formulas since Lord Rayleigh (1890's) are basically the
same.  Patton actually has found that bigger pinholes than what most of the
rest of us consider "optimum", gives him sharper images.  OTOH, you have
Larry Bullis  going the oposite way, that is, he finds that smaller pinholes
give him sharper results.  Myself, my eyes, rather, are more inclined to
align with Larry than with Patton.

>  or
>  http://www.huecandela.com/hue-x/pin-pdf/Prober-%20Wellman.pdf  for the
> white paper study.
> Also the formula can correct for pinhole to subject distances, for
Close-up
> and Micro pinhole pictures.

The Prober-Wellman Formula is exactly what science has been telling us the
optimal pinhole formula should be   D= SQRT (2.44 * Lambda * F) , the SQRT(1
/ M+1 ) factor is a sort of "bellows factor" as I explained it in a post
back in Oct last year:
http://www.pairlist.net/mailman/private/pinhole-discussion/2001-October/0042
23.html

Guillermo

Re: [pinhole-discussion] Question on image circle and medium format pinhole camera design

[Guillermo]

- Original Message -
From: "Philip willarney" 

> If the edge is a slow fade from picture to dim picture
> to black, then it's falloff.  Pinholes as such don't
> have an image coverage circle --

That is correct, the image circle is determined by how many stops at the
edges we are willing to tolerate.  Those 3X or 3.5X the focal length
coverage mentioned everwhere, have no meaning whatsoever, IMO.

Guillermo

Re: [pinhole-discussion] Question on image circle and medium format pinhole camera design

[Guillermo]

- Original Message -
From: "Fox, Robert" 

> I'm thrilled with the results! The proofs are properly exposed (surprise
> given I was using a flap for the shutter and counting the seconds) on
Ilford
> XP2 film (iso 400). I used f64 as the base exposure reading, then
multiplied
> by 6.3, which worked great.

Bear in mind that multiplying the f/64 by 6.3 or 6.48 (if you want to be
more exact) will give you a reciprocity uncorrected value for the f/stop of
your camera.  If by any chance you noticed that the longer the exposures the
thinner the negatives, that may indicate is time to correct for reciprocity
at those levels of long exposures. I'd suggest you take some notes when
shooting.  Proof print may or may not show up the underexposure, some may
even benefit from it!!

> Question:  my images are all circular, cutting off the corners cleanly of
> the square print. Is this because the image circle is too small for the
> film? I'm wondering if the circular edge of the front plate is being
picked
> up on film, since the edge sticks up about 1/4 inch.

Any time the corners are "cut" cleanly as you mention, it is probably
mechanical vignetting, the front plate is obviously in the way.  You could
check for mechanical vignetting by opening the rear and aiming the camera to
a bright light while having your eye, the corner of the opening (6x6) and
the pinhole line up, if you can't see light coming in thru the pinhole, then
you have vignetting.

Guillermo

Re: [pinhole-discussion] Does Pinhole-Discussion have an archive?

[Guillermo]

- Original Message -
From: "Andrew Amundsen" 

> ...how do we access the archives? Could someone post a link?

Andrew:

You will see a link to the DISCUSSION page, at the foot of each posting, go
there and 3/4 down the page there is a link to archives. There are 2
categories of archived messages: those posted previous to 08/22/2000 and
those posted after.  The former are easier to search than the latter,
unfortunately.

Guillermo

Re: [pinhole-discussion] SX-70

[Guillermo]

- Original Message - 
From: "MARK POWER" 

> Folks,
> I've tried to dissect a SX-70 for some pin hole fun, but to no avail
> i.e., I'm frightened of breaking it all together.  Any hints?

Mark, "The Hacker's Guide to SX-70" has the answer for you:

http://www.chemie.unibas.ch/~holder/SX70.html

Guillermo

Re: [pinhole-discussion] re pinhole size

[Guillermo]

- Original Message -
From: "Paul Prober" 
>
> A pinhole with the minimal thickness the expected at 120 degree [+/-60]
view
> angle 1 stop roll off at edge

Paul, I have visited your PinPlus site but couldn't see any picture of your
cameras.  Are your cameras curved film plane?  If the answer is not: I
always thought that the fall off or roll off (as you call it) at the edges
of a 120 degrees {+/- 60} would be 4 stops, but may be I have been mistaken.
Could you please explain, on or off the list, how you came up with just 1
stop fall off?

Many thanks,

Guillermo

Re: [pinhole-discussion] pinhole size

[Guillermo]

Michael,

Pinholes are "afocal", meaning: they don't have focal length, per se.  You
can use them to whatever distance pinhole-film you wish, knowing that if you
don't use them to their "optimum" distance, results will be "less-sharp",
which depending on the photographer intentions could be good or bad for your
resulting image.

Knowing that a pinhole can be used at any distance, again, they are afocal,
the fall-off is not caused by its size, but by 3 different factors: first:
light on the film plane decreases as the distance pinhole-film increases,
distance at the center is shorter than distance at the edges of the film,
therefore you'll have fall-off as you go off film center.  secondly: seen
from the center of the film the pinhole looks round (assuming you made it
round), but seen from the edges, it would look oval, that translate into
less area for light to go thru, that too causes fall-off.  Lastly: light
falling at the edges, falls at an angle on the film, therefore covers a
bigger area of the film, that too, causes fall off.  Geekly speaking :) the
fall off at the edges will be a factor of the function COSINE to the 4th
power of half the total angle of view of your camera, in your case that
translate to just over 3 stops.  BTW, glass lenses are not exempt of this
COSINE^4 condition, that is why for wide angle lenses manufacturers also
make special filters to go with them and that correct the fall off at the
edges by causing fall off at the center (forgot their name, center filters I
think).

If you were to use a pinhole optimum for 73mm, your fall off will be the
same, the fall off is only a function of the angle of view, in other words,
the wider the angle of your camera, the more fall off.  Your camera has 109
degrees angle of view, the format diagonal is just 2.8 times the distance
pinhole-film, BTW.

Optimum does not mean longest, it means "if you want the sharpest images
possible use this distance", longer or shorter that optimum and the
resolution suffers.

The only way to get less fall-off is to make the film or paper to conform to
a cylindrical shaped film plane and position the pinhole at the center of
the circle describing the half cylinder, there are some examples here:
http://www.cyberbeach.net/~dbardell/pinhole.html
The reason why such cameras have less fall off is that the distance
pinhole-film is the same from center to edge of film and also the light
always falls perpendicular to the film so it doesn't have to cover more area
(as explained above).

Something else that contributes to a fall-off is the thickness of the
material the pinhole is made of and whether it has burrs around its edges.

Guillermo

- Original Message -
From: "Michael Healy" 

> I bought the 12-"lens" set from Pinhole Resourses, and I've been using the
> .0102"/.259mm pinhole on my 4x5. This one's claimed optimal focal length
is
> supposed to be 48mm. I am using it with a recessed lensboard to a length
of
> about 50mm. That's the closest I can get even w/ a bag bellows.
>
> The results are fantastic. I love the focal length. Unfortunately, its
> fall-off is quite noticable. No vignetting, but the fall-off is about
1.5-2
> stops from center to edge. So I think I have to try the next one of the
> bunch, the one whose optimal focal length is reported to be 73mm. That
seems
> like quite a jump, though.
>
> Before I try this at a shorter bellows length than 73mm, has anybody done
> this? Will I have problems just shooting this at, say, my 50mm (w/ bellows
> compensation)? Does their "optimal" mean "longest"? That's what the 48mm
> seems to mean, that if you go even to 50mm, you'll have fall-off. Anybody
w/
> experience of this? If this works, should I consider ordering a 50-55mm
> pinhole to fit my 4x5? I really like the weird, extreme result from the
> short one -- it's just that the light fall-off makes cyanotypes very
> difficult to print. I'm anticipating that albumen won't work much better.
>
> Thoughts?
>
> Mike Healy

Re: [pinhole-discussion] holga source in Chicago?

[Guillermo]

- Original Message - 
From: "D. Hill" 

> Calumet stocks them, do they have a storefront?

Yes they do, as per their web site:

Manager:  Greg Hamlin
Address:   N Cherry St.  Chicago, IL 60622
Phone:  312-440-4920
Fax:  312-664-1736
Hours:  Monday-Friday 8:30 a.m.-5:30 p.m.

Guillermo

Re: [pinhole-discussion] Polaroid Reciprocity

[Guillermo]

- Original Message -
From: "ROBERTSON,TRAVIS J" 

> whatever geek

Travis,
   I admit to have had to recur to the dictionary and the web to
understand the meaning of geek, I am not really fluent in English, you know.
I found that originally, a geek was a carnival performer who bit the heads
off chickens (pre-1900's), during a good portion of the XX century it had a
despective connotation, but as the mainstream culture became more dependent
on technology and technical skill, mainstream attitudes have tended to shift
towards a meaning of "grudging respect".  So, I'd take your 2 words as a
compliment.

But please Travis, do no let my geeky answers to Jason Rusell's questions
prevent you from contributing your own and perhaps more understandable
answers to his questions.  After all, I too am in this list to learn from
what other have to contribute.

Guillermo

Re: [pinhole-discussion] Polaroid Reciprocity

[Guillermo]

- Original Message -
From: "Jason Russell" 
>
> The corrected time you gave me worked very well.   Thank you!
>
> However, I want to clarify one thing...
>
> Did you go to the Polaroid website to get the numbers to plug into the
> WinCurveFit program?  Did you just pull the numbers from the displayed
graph
> and plug them into the program and extend the curve?  Is that how that
> works.

Jason, altho I could have used the graph to get some "indicated versus
corrected" values, that graph is just too coarse and since some values are
already given in the "Reciprocity Performance" table, that's what I used.
Now, that table (or graph) gives you corrected values in terms of extra
stops of Exposure Adjustment,  so we need to translate the indicated
exposures to corrected exposures in seconds.  For full stops it is easy, you
double the indicated exposure for each stop of adjustment, but what about,
for instance, the corrected exposure for an indicated 16 secs and an
adjustment of  +1 2/3 stops?  To do it, you have to use the following
equation:

I = indicated time
T = corrected time
n = exposure correction in stops
^ = raised to the power of (need scientific calculator to do it, I use
CALC98, freeware program downloadble here
http://www.calculator.org/download.html)

T = I * (2 ^ n)

In the case of 16 secs and 1 2/3 stops adjustment, it would be:

T = 16 * (2 ^ 1 2/3)
T = 16 * (2 ^ 1.)
T = 16 * 3.17465
T = 50.79 secs

Once you have all the corrected values in seconds, feed the indicated and
corrected values to the WinCurveFit program.

I have to mention that I don't bring a calculator with me when I go out to
make exposures, I prefer to make a graph, very much like this one
http://www.kodak.com/global/en/professional/support/techPubs/f9/f002_0062gc.
gif  and use that to find corrected times.

Guillermo

Re: [pinhole-discussion] Polaroid Reciprocity

[Guillermo]

- Original Message -
From: "Jason Russell" 
>
> Will the equation change with different types of film?

The equation is just a math model of the reciprocity correction curve, the
latter is just a graphic representation of the discrete values, either given
by manufactures (like the ones given by Polaroid for the film in question -
Polapan type 72) or obtained by us thru experimentation.  Since each film
has its own reciprocity characteristics, each film would have its own
equation.

> Or do I just plug
> the indicated time into the equation to get a starting point?  If it does
> change, which numbers will be different and how do I figure them out

All the coefficients change.  You can find them by doing a Regression
analysis of the known reciprocity correction values, I use the Least Square
polynomial method, here is a hint on how to do that:
http://www.efunda.com/math/leastsquares/lstsqrmdcurve.cfm , for those of us
confused by the above, using a program like WinCurveFit
http://www.krs.com.au/wcf.html is "a good thing", that is what I used to
give you the answer BTW.

Guillermo

Re: [pinhole-discussion] re:pinhole nude

[Guillermo]

- Original Message -
From: "Paul Prober" 
>
> Note! By using flash there is no recopicity failure. The effect is the
same
> as opening the shutter for 1/1,000 of a second each time the flash is
fired.

Sure, there is a "reciprocity" like effect, its name is Intermittency
Effect.

Guillermo

Re: [pinhole-discussion] Polaroid Reciprocity

[Guillermo]

- Original Message -
From: "Jason Russell" 

> I was wondering if anyone could help me with Polaroid Reciprocity.  I just
> recently started shooting with a Santa Barbara (2 inch Super Wide) with a
> Polaroid back.  Right now I'm shooting with Polapan 400 B&W (72).  I've
done
> most of my shooting outside and the exposures have all been less than six
> seconds.  I wanted to try shooting inside under much lower light.  I'm
just
> not sure how much I need to compensate for reciprocity.  I checked out the
> info on Polaroid's site, but I'm still a unclear.
> Has anyone else shot with this film or a similar film that could give me
an
> idea of how much time to add.
> The shot I want to shoot right now, by my calculations is about 2 and a
half
> minutes without compensating for reciprocity.

Jason:

I have not used the film, nevertheless here is my suggestion:

Short answer: for indicated 2.5 minutes you should give 17 minutes 3 secs.

Long answer: As you can see on the Reciprocity Performance chart, the
effective film speed decreases (as expected) as the indicated exposure time
increases, the exposure adjustment column tells you how many stops you
should increase the indicated time.  For 4 secs, for instance, the exposure
adustment is 1 stop, that means you should double the time to 8secs.  I made
some math calculations (best curve fit) and they predict that when the
indicated exposure time is 150secs (2.5minutes), the effective film speed
will be  ISO-58.6, which in turn will need an exposure adjustment of 2.77
stops, for a total of 1023secs or 17 minutes 4 secs (150 x 2^2.77 = 1023).
If you want some other times, use the following formula:

T = corrected time
I = indicated time
* = multiplication sign

T = ( 0.021 * I * I ) + ( 3.708 * I ) - 4.89

CAVEAT: the above suggestion is just an educated starting point based on the
Polaroid published information, YMMV.

Guillermo

Re: [pinhole-discussion] zone plate

[Guillermo]

Stanford is incorrectly spelled, it should be STANFORD not STANDFORD.

Guillermo

- Original Message -
From: "John Fisher" 


> Would you check the URL? I have tried to open the site.But haven't had any
> luck. thank you
>
>
> >From: "Paul Prober" 
> >Reply-To: pinhole-discussion@p at ???
> >
> >  Chris Patton at Pinhole and beyond has a zone plate area. The site
> >address
> >is
> >www.standford.edu/~cpatton/zp.html  There is many zone plate "lens", plus
> >formulas for focusing the lens to subject.
> >Paul Prober

Re: [pinhole-discussion] Zone plates for a body cap

[Guillermo]

- Original Message -
From: "Guillermo" 
>
> I gather that by "aperture of the zone plate" you mean the size of each of
> the rings.  Mr.Pinhole formula is what the scientific community uses for
> their high-tech uses of zone plates and my non-scientific tests (focusing
> aerial images produced by zoneplates) have confirmed that.  Other use
> slightly different formulas.

I was reading my own post and it seems not to be too clear.

What I meant was that when I mount zone plates on my 4x5 view camera and
focus on the aerial image until it is a "sharp" as they would be, the
distance zone plate to film plane matches very closely with what the formula
Radius = SQRT(wave length x focal length x ring#) would predict.

Now, the formula can also be written as Diameter = 2 x SQRT(wave length x
focal length x ring#).  Some people use formulas slightly diferent, what
they change is that number "2", Patton for instance, uses 1.86
http://www.stanford.edu/~cpatton/zoneplatemath.htm

Guillermo

Re: [pinhole-discussion] Zone plates for a body cap

[Guillermo]

- Original Message -
From: "Beaker" 

> Guillermo- how do you figure out the aperture of a zone plate? Mr.
> Pinhole mentions this formula:focallength * ring)>. I was guessing that this would give a good number
> to start with. Is this a good guess?

I gather that by "aperture of the zone plate" you mean the size of each of
the rings.  Mr.Pinhole formula is what the scientific community uses for
their high-tech uses of zone plates and my non-scientific tests (focusing
aerial images produced by zoneplates) have confirmed that.  Other use
slightly different formulas.

> One last thing- I've never worked with zone plates before, or even have
> litho negatives made, so we will learn together what works, and what
> doesn't!

Just one more suggestion, try making zone plates whose number of clear rings
give you f/stops that are equal or slightly smaller (numerically) than a
full stop, this will facilitate exposure calculations.

Guillermo

Re: [pinhole-discussion] using filters

[Guillermo]

- Original Message -
From: "Jeremy Jeffs" 

> I've been shooting B+W landscapes on a pinhole camera.  To bring out
clouds
> I've been using a yellow filter behind the pinhole - in front would mean
> than every speck of dirt is in focus. My problem is that specks of dirt
cast
> a blur/shadow on the negs.  I've tried vigilant cleaning but can't seem to
> eradicate them. Any suggestions on keeping contrast in the sky without a
> filter? Or alternatively how to use a filter without rendering every speck
> of dirt?

Don't mount the filter on the camera, rather hold it in front of the pinhole
and keep moving it for the duration of the exposure.  The larger the filter
the easier this is done.

Guillermo

Re: [pinhole-discussion] Zone plates for a body cap

[Guillermo]

- Original Message -
From: "Beaker" 

> I'm thinking of getting a sheet of Zone Plates made for a Pentax K
> mount body cap (optimized for 43 mm). Would anyone be interested in
> buying any? The reason I ask, the negative will cost something like $50
> to $75, (the shop has a $50 minimum.) and I would like to spread the
> cost out a little. For a little more to cover the cost of a body cap, I
> could send out the finished article. The negative isn't made yet- I'm
> just trying to gauge the interest, so the price is still "to be
> determined".

A sheet made by an image setter can fit lots of ZPs, you don't have to have
the whole sheet full of 43mm ZPs, I would suggest you make some other focal
lengths as well. 65mm for instance is perfect for attaching it to the back
of the shutter of a Lubitel.  Another possibility, which is not mutually
exclusive with the one previously mentioned, is to make similar focal
lengths ZPs but with different number of rings, which will give you
different f/stops, I.E., a 43mm ZP with 9 total rings is f/64 (aprox) but a
19 rings one is f/45 and would probably have more of that ghostly effect.

I make my own ZPs using lith film, otherwise I'd be joining you,
nevertheless I recognize this as a good chance for those that have not
experimented zoneplate photography to try it with very minimum investment
and help you share the cost in the process, a win/win scenario if you ask
me.

Good luck.

Guillermo

Re: [pinhole-discussion] LARGE FORMAT f STOP QUESTIONS

[Guillermo]

- Original Message -
From: earthecho
Hello, Frazer Bryant here - New member from England.

Hello Frazer and welcome to the list.

>The sheet Film size is 8 and a 1/2 inch X 6 and a 1/2 inch.
>(I will be using paper negs.)

I have one of those, only mine is 6 1/2 X 8 1/2" !!!
Just kidding, Frazer.  :-)

>Q1  What Dia. pinholes should I use for a) wide angle, and super
>wide angle images, and, what would be their corresponding fstops ?.

>Q2  What would be the appropriate distances between negative and pinhole
>for the above pinholes ?.

The above question should probably be formulated in reversed order, in other
words, you first want to know what focal lengths constitute super wide and
wide, then what diameters "should" be used for them and finally what f/stops
would they be.

Wide: 120mm to 180mm
Super Wide: anything under 120
In general, you could multiply a 35mm format focal length times 6 and that
would be the equivalent to 6.5X8.5 format, I.E., 50mm is normal for 35mm
formt, the equivalent for your half plate camera would be 50x6 = 300mm
The so called "optimum" diameters would be given by:
diameter in mm = 0.03679 x SQRT ( focal length in mm)
SQRT stands for square root.
F/stops could be found by dividing the focal length by the diameter of the
pinhole you are using.
The appropriate distance distance between pinhole and film plane is the same
as the focal length.

Download David Balihar's PinholeDesigner at
http://www.pinhole.cz/en/pinholedesigner/ , excellent tool to help you with
diameters, focal lengths, angles of view, f/stops, etc.

Read my articles:
http://members.rogers.com/penate/pinsize.htm
http://members.rogers.com/penate/diameter.htm

Peruse the resources page at Pinhole Visions
http://www.???/resources/ and the one at the World Wide
Pinhole Photography Day http://www.pinholeday.org/

Guillermo

Re: [pinhole-discussion] www.pinhole.cz

[Guillermo]

David,
  Great site and above all, outstanding and functional tool you are
making available, I am talking about the PinholeDesigner, of course.  Later
I will pay your site a more thorough visit and let you know any other
comment I have.

Thanks.

Guillermo

- Original Message -
From: "David Balihar" 

> I'd like to invite you to have a look at my new Internet pages
> www.pinhole.cz
> Apart from examples of photographs and pinhole cameras, you will also find
> several texts, for example, about the curious Dirkon paper pinhole camera,
> or the PinholeDesigner program which simplifies various calculations and
> enables you to save the zone plate in PDF format.
>
> I look forward to hearing your views and comments
>
> David Balihar

Re: [pinhole-discussion] 4x5 back needed

[Guillermo]

- Original Message -
From: "D. Hill" 

> Does anyone have a spare 4x5 spring or grafloc back?
> I really need one, write me with what you want for it.

I'd suggest you check eBay, I just did that myself and saw couple of backs
or reducing backs that may be just what you want.

I bought a wooden homegrown 11x14" spring back with GG, but have not been
able to locate a holder for it, yet. I could let that spring back go for a
price but that back is a bit bigger! than what you are looking for.

Guillermo

Re: [pinhole-discussion] 4x5 film

[Guillermo]

> On Thu, 17 Oct 2002, George L Smyth wrote:

> > Not "one of" but "the" best book on the subject.   I've got a copy,
but was
> > suprised to hear that it was online (I wanted to do that long ago, but
couldn't
> > get permission).  The above link I see as dead.  Could you check it and
let me
> > know if the book is indeed online?

Longtime ago I downloaded the book (lots of htmls and gifs) and have it in
my disk drive, it is about 1.5MB ZIP compressed.  There is also a PDF
version here http://www.ushist.com/props/inc/albumen_salted_paper_reilly.pdf

Guillermo

Re: [pinhole-discussion] weddings

[Guillermo]

- Original Message -
From: 


> Thanks for all the info. I could not get to 'stanford' site and the 'Zero'
> site did not give enough details.
> But I think a zone plate seems to be similar to a Fresnal Lens.
> If not, then further enlightenment is needed.
> Ellis

Mark Iterrante mentioned my sites:

Images: http://members.rogers.com/penate/ZP120.html
Article on the subject: http://members.rogers.com/penate/zoneplate.html

If something in the above article you don't understand of if you have any
questions after having read it, pls post a question, either here or directly
to my email address  pen...@rogers.com

Guillermo

Re: [pinhole-discussion] Pinhole & enlarging

[Guillermo]

- Original Message -
From: 

> The issue is the degree of enlargement. Enlarging 35mm to 4x6 increases
the
> image area 16 times. Increasing a 4x5 to 16x20 increases the area only 4
> times.


4x5 to 16x20 is also a 16X increase in area.
You are right, the issue is the degree of enlargement and I'd add, the
resolution you start with.

Guillermo

Re: [pinhole-discussion] Pinhole & enlarging

[Guillermo]

- Original Message -
From: "Uptown Gallery" 
>
> If one did MF (4x5 or 5x7) or LF (8x10) sheet film pinhole (and had an
> enlarger large enough), what are the prospects for enlarging?

Murray,

4x5 & 5x7 were also LF last time a checked.

> I was very unhappy with 4x6 prints from 35mm pinhole.

Could we see some of those results?

Prospects of enlarging 4x5 and up, are excellent
Prospects of enlarging 35mm format to up to 8x10 are fair to good (at
least), but you have to shoot for the intended print size and  properties.
I wish I can show you some new results of enlarged 35mm negatives, but I
haven't done pinhole or any other type of photography in ages :-( , last
image I did was for a workshop I gave back in Nov/2001, the negative was a
35mm format size PAPER  NEGATIVE taped inside this ugly camera:
http://members.rogers.com/penate/cameras/14f.jpg (a disposable modified
camera) and then enlarged/cropped to 6x6", here is the result:
http://members.rogers.com/penate/doll6x6.jpg  (the negative is shown at a
greater magnification, than the 6x6" print itself).  I'd call that a fair
minus result, but bear in mind the original was a 35mm paper negative.  This
other example made back in 1996, is from a 35mm film negative using the same
ugly camera above and enlarging it to about 8x10":
http://members.rogers.com/penate/fire.html , I'd call that a fair plus to
good result, obviously I am not talking about artistic merits but whether
the image "falls apart" or not after enlarging it.  The pinhole size, btw,
was "optimum" for the focal length of that camera.

Guillermo

Re: [pinhole-discussion] Polaroid Pack Film Mechanics?

[Guillermo]

- Original Message -
From: "Gordon J. Holtslander" 

> Polaroid makes a pinhole camera kit - I wonder if your film would work
> with it?

Gordon: If I am not mistaken, the Pol-Pin takes 3.25x4.25 packs same as the
ones the holder 405 uses.  The famous pos-neg 665 is one example of those
kinds of films.

BTW, Michael, what about renting a Pol 550 back for a day and shooting away
as if there is no tomorrow, until all boxes are gone!!

Guillermo

Re: [pinhole-discussion] Polaroid Pack Film Mechanics?

[Guillermo]

Michael,
 This site may help you understand how a Polaroid pack works:

http://www.theskeltons.org/polaroids/film.htm

Guillermo


- Original Message -
From: 
>
> Anyone have any experience with the mechanics of Polaroid pack film?
>
=> So, here I am with many, many boxes of Polaroid 553, Polapan ASA100 4x5
pack
> film, and no way to use it (yet).  I can build a camera out of any damn
> thing, but a homemade Polaroid back presents a bit more of a challenge.

Re: [pinhole-discussion] Re: sheet film instead of photo paper

[Guillermo]

- Original Message -
From: "George L Smyth" 
> >
> > << There's nothing to stop you from using 4x5 sheets of paper with a 4x5
film
> > back right? >>
> >
> > No...and you can enlarge them in a 4" x 5" enlarger...and in color too.
> > leezy
>
> How would you enlarge paper via your enlarger?

I taught a pinhole workshop for a local camera club this past Thursday.  One
of the exposures I made was a paper negative 35mm format!!  which I then
proceeded to enlarge to 6"x6" size (a center portion of the negative) .  I
had no problem doing so and IMO it held up OK, even when using satin finish
B&W paper, glossy paper would give "better" results I'd assume.  BTW,
focusing on the grain of the photo paper was absolutely not a problem, it
was very much like focusing on film grain.

Never enlarged paper before, it is definitely doable.

Guillermo

Re: [pinhole-discussion] DIana Camera & Ebay

[Guillermo]

- Original Message -

> DIANA F Camera w/ lens cap
> http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1299031604
>
> Currently at $100USD.
> ?  ok I don't understand...

I know what you mean when you say "I don't understand".  And like you Andy,
I know they are CULT-llector cameras and very IN with the so called ART
communitynevertheless, I still is hard to understand that price for it!!

Guillermo

Re: [pinhole-discussion] zone plate question

[Guillermo]

- Original Message -
From: "Richard M. Koolish" 

> I'm not sure I would describe the workings of a zone plate this way.
It
> doesn't matter where in the zone plate (or pinhole) the light passes
> through.  It doesn't bend at one place and not in another.  The way
you
> think about a zone plate or pinhole is that every clear point acts
like a
> spherical wave is generated there.  Then from any point in the image
plane,
> you add up all the contributions to the intensity at that position
from all
> the individual contributing points of the zone plate or pinhole.  Some
> waves will be in phase and reinforce each other, and some waves will
be out
> of phase and destructively interfere.  In the "simple" case of a
pinhole,
> you discover, that a point source of light in a subject does not
generate a
> true point of light at the film or even a simple disk, as if a beam of
> light came through.  Instead, you get the clasic diffraction pattern
of a
> point, i.e. a central disk (the Airy disk) surrounded by diffraction
rings.
> Note that every aperture produces diffraction.  Even the most perfect
lens
> can't focus a point source into an image point.  Normally you don't
see
> this because the diffraction pattern is so small.  An f/10 lens
produces
> an Airy disk of only .0134 mm for green light.  On the other hand, if
you
> place a very small pinhole, say 50 microns (.05 mm) 100 mm away from
the
> film and shine a red laser pointer at it, you will get a diffraction
disk
> of about 3 mm in diameter.
>
> The zone plate has a lot of chromatic aberration.  That is, it can't
> focus different colors of light at the same place.  That's what causes
> the characteristic glow around bright objects in a zone plate
photograph.
> One color may get focussed sharply and the others will get spread out
> into disks of various sizes around the sharp point.  I can't speak to
the
> issue of how much this changes with the number of rings in the zone
plate
> since I haven't done any research on this.  It would be an interesting
> and fairly easy experiment to try.
>
> Dick Koolish  (kool...@bbn.com)
>
> ___
> Pinhole-Discussion mailing list
> Pinhole-Discussion@p at ???
> unsubscribe or change your account at
> http://www.???/discussion/
>

Re: [pinhole-discussion] zone plate question

[Guillermo]

- Original Message -
From: "Kate Hudec" 


> I was interested in Guillermo's recent post about the relationship
> between number of rings and zone plate image sharpness.  I have a
> converted Lubitel with 75mm focal length.  If I wanted a camera with
> MORE distortion (which I understand from Guillermo's post would also be
> a faster camera), would I need a camera with a longer or shorter focal
> length?  Thanks in advance.

Kate,   I don't think I mentioned distortion in my post.  A faster ZP has
more clear rings, but that causes no distortion, the ZP camera still is free
of linear distortion (at least).  The increased number of clear rings
increase the
ratio noise/signal, tho.  Noise is the light that reaches the film without
having suffered diffraction, therefore do not contribute to the "sharpness"
of the image, this is the light mostly responsible for the characteristic
"glow" of a ZP image.  Signal is the light that grazes the edges of the
rings, suffer diffraction and is "focused" on the film plane, this light is
the one resposible for the "sharpness" of the image.

As far as getting distortion using longer or shorter focal length: Very wide
angles of view are considered distorting because of the radically altered
perspective compared to what we are used to see with our own eyes.  If this
is the kind of distortion you refer to, then, with a 6x6 film format
Lubitel, you would need to have (IMO) the lens (pinhole or ZP) as least as
close as 30mm from the film plane (closer would be better).

I too have a modified Lubitel and I believe that even carving the front of
the camera and recessing the lens, it'd be impossible to install the lens
30mm or less from the film plane w/o having vignetting caused by the viewing
lens.  If you want to sacrifice the composing help the viewing lens afford,
then I think it may be doable but it'd easier if you get a cheaper 6x6
folder camera remove the bellows and modify it as pinhole/ZP. Something like
this one I made:
ftp://penate:athx2...@members.home.com/penate/cameras/12.jpg or this
ftp://penate:athx2...@members.home.com/penate/cameras/6x6.jpg

Hope it answers your questions.

Guillermo

Re: [pinhole-discussion] zoneplates

[Guillermo]

- Original Message -
From: "Gordon J. Holtslander" 
>
> some quick questions for the zone plate experts.

I am not an expert nor claim to be one, but your questions are right up my
alley!!

> tedious. 1/2 hour for somewhat under-exposed negatives in direct afternoon
> sun.  I want to speed this up somehow.
> How much faster does a zoneplate work than a pinhole on average?

They are as fast as you want/make them to be, at a price tho.  The more
clear rings they have the faster they are, but the larger the noise/signal
ratio.

> I want to try making a zone plate for this and other cameras.  I was going
> to make the zone-plate on ortho film.  I am wondering if its possible to
> make one master zone plate image and project from an enlarger, this image
> onto another sheet of ortho to scale it up or down make zoneplates for
> diffferent focal lengths.

I think is doable, but I rather take pictures of a "paper zoneplate" at
different distances with a 35mm SLR camera.

> I guess this depends upon whether or not the zoneplate for different focal
> lengths is proportional the same.  Is it?  Or is the ring relationship
> unique for each focal length?

They are proportional.  If "B" is the intended ZP focal length, "A" is the
master ZP focal length and "C" is given by  C = B/A  then the ring diameters
formula for Zoneplate B will be:

D = Da * SQRT(C)

where Da = ring diameter for master zoneplate.

(complete explanation upon request)

> Is the "sharpness" of the zoneplate image governed by the number of rings?
> How close can one get the resolution of an image created with an ideal
> pinole diameter?

Very close, just reduce the # of rings until you are satisfied with the
sharpness, but then you are trading off "fastness" for "sharpness"

> My other question is has anyone had success creating and outputing these
> completely digitally -Is there a printer that can create a fine enough
> resolution image to make good zoneplates?

I think Zernike makes his ZPs digitally, don't hold your breath waiting for
him to contribute to this or any other thread, though (hope he proves me
wrong!!).  If I were to speculate. he may have a comercial image setter shop
giving him a complete sheet of film with lots of ZPs of different focal
lengths as output from a digital file he may produce with Corel or similar
program. I never seen one (digitally produced ZP) but I guess they have
jagged edges compared with "analog" made ZPs, that may or may not have any
consecuences on the final image they produce.  And no, I don't think a
consumer or low end comercial printer would work. Should you find the
opposite, let us know, pls.

Guillermo