Re: [pinhole-discussion] f stops

2001-10-30 Thread Ricardo Wildberger Lisboa
Beware of virus !

Ricardo.


- Original Message -
From: Guillermo pen...@home.com
To: pinhole-discussion@p at ???
Sent: Tuesday, October 30, 2001 4:55 PM
Subject: Re: [pinhole-discussion] f stops



 - Original Message -
 From: Gregg Kemp gregg.k...@sas.com
 To: pinhole-discussion@p at ???
 Sent: Tuesday, October 30, 2001 1:02 PM
 Subject: RE: [pinhole-discussion] f stops


  I wrote to Philip asking if he was having a problem with his mail and if
I
 could help.  I haven't gotten a reply, but noticed he continues to send
 empty messages.

 He's also sending blank msgs to the cameramakers list, also

 and lots of them!

 Guillermo


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Re: [pinhole-discussion] f stops

2001-10-30 Thread Ricardo Wildberger Lisboa
Yes, all Philip messages are blank.

Ricardo.


- Original Message - 
From: Philip Arny philip.a...@tpl.org
To: pinhole-discussion@p at ???
Sent: Tuesday, October 30, 2001 3:58 PM
Subject: Re: [pinhole-discussion] f stops


 
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Re: [pinhole-discussion] f stops

2001-10-30 Thread John Yeo
 So, the ratio between the diameters of consecutive stops is the square
root
 of two.  Because in the F/stop formula, the diameter of the opening is in
 the denominator, the actual f number increases by a factor of two, as the
 diameter decreases by a factor of two.

oops.  factor of the square root of two.

John




Re: [pinhole-discussion] f stops

2001-10-30 Thread ragowaring
on 30/10/01 3:06 pm, Guillermo at pen...@home.com wrote:

 
 - Original Message -
 From: ragowaring ragowar...@btinternet.com
 
 Anyway, enough of an introduction; could anyone please tell me how to
 calculate the natural progression of f stops doubling exposure from one
 number to the next, or post a list of these.
 
 They follow a geometric progression that make the f/stops increase by a
 factor of square root of 2
 
 Need a more complete explanation?  let me know.
 
 Guillermo
 
 
 
 
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Wow!, is it really that simple. Of course, it all makes sense now and it
will be very helpful.  Thankyou for your replies.  If it is not too much
trouble a complete explanation would be very welcome Guillermo.  Thankyou
also to Murray for how you calculate the exposure for a given camera; this
method will help me relate one camera to another; also thanks to Bill
Erikson. 

I too don't know what happened to Philip Arny but he has sent me masses of
empty messages.  I guess if the cat continues on the keyboard this way it
may come up with one of Shakespear's plays orthe meaning of life, universe,
everything.

Alexis 










Re: [pinhole-discussion] Ilfochrome

2001-10-30 Thread Lusi
thanks for the comment


Re: [pinhole-discussion] f stops

2001-10-30 Thread Guillermo
- Original Message - 
From: TSHACK tsh...@silver-bayou.com
 
 How would I join the cameramakers list?  Is that a newsgroup, or an email
 list?

Email list, similar to our beloved pinhole list.

Here is some info on it:

 Cameramakers mailing list
 cameramak...@rmp.opusis.com
 http://rmp.opusis.com/mailman/listinfo/cameramakers

Guillermo




RE: [pinhole-discussion] Philip Arny

2001-10-30 Thread Gregg Kemp
I'm guessing first contact... either an alien life form or the first cries from 
an artificial intelligence.  Hold on, Philip - we are trying to reach you! 

Actually, I think he has an autoresponder set to reply to any message he 
receives.  I had to unsubscribe him.  Hopefully, he'll come home from work, 
find out what has happened, and be in touch.

Gregg

 He's also sending blank msgs to the cameramakers list, also
 
 and lots of them!
 
 Guillermo




Re: [pinhole-discussion] f stops

2001-10-30 Thread TSHACK
  I wrote to Philip asking if he was having a problem with his mail and if
I
 could help.  I haven't gotten a reply, but noticed he continues to send
 empty messages.

 He's also sending blank msgs to the cameramakers list, also

How would I join the cameramakers list?  Is that a newsgroup, or an email
list?






Re: [pinhole-discussion] f stops

2001-10-30 Thread Guillermo
- Original Message -
From: Gregg Kemp gregg.k...@sas.com
To: pinhole-discussion@p at ???
Sent: Tuesday, October 30, 2001 1:02 PM
Subject: RE: [pinhole-discussion] f stops


 I wrote to Philip asking if he was having a problem with his mail and if I
could help.  I haven't gotten a reply, but noticed he continues to send
empty messages.

He's also sending blank msgs to the cameramakers list, also

and lots of them!

Guillermo




[pinhole-discussion] cat on the keyboard?

2001-10-30 Thread Gregg Kemp
I've written him for more information, but in the meantime I've blocked him 
from posting to the list.  Pretty strange...

Gregg

 -Original Message-
 From: TSHACK [mailto:tsh...@silver-bayou.com]
 Sent: Tuesday, October 30, 2001 1:33 PM
 To: pinhole-discussion@p at ???
 Subject: Re: [pinhole-discussion] f stops
 
 
 His messages to me directly are blank also.
 
 
 - Original Message -
 From: Gregg Kemp gregg.k...@sas.com
 To: pinhole-discussion@p at ???
 Sent: Tuesday, October 30, 2001 10:02 AM
 Subject: RE: [pinhole-discussion] f stops
 
 
  I wrote to Philip asking if he was having a problem with 
 his mail and if I
 could help.  I haven't gotten a reply, but noticed he 
 continues to send
 empty messages.
 
  Maybe it's Philip's cat playing with the keyboard(?)



Re: [pinhole-discussion] f stops

2001-10-30 Thread TSHACK
His messages to me directly are blank also.


- Original Message -
From: Gregg Kemp gregg.k...@sas.com
To: pinhole-discussion@p at ???
Sent: Tuesday, October 30, 2001 10:02 AM
Subject: RE: [pinhole-discussion] f stops


 I wrote to Philip asking if he was having a problem with his mail and if I
could help.  I haven't gotten a reply, but noticed he continues to send
empty messages.

 Maybe it's Philip's cat playing with the keyboard(?)






Re: [pinhole-discussion] f stops

2001-10-30 Thread Philip Arny


[pinhole-discussion] Kudos and a Query

2001-10-30 Thread Howard Wells
I know I am not alone in my appreciation of the tremendous resources
available on this list, Guillermo being a prime example.  I always learn
something from his posts. Thank you Guillermo, thank you all for your
intelligence, artistry and civility. It is always an inspiration.

I've already altered an ancient Leonardo to be a close-up camera. I've
also been using a PhotoTechnicalGroup (f512) camera with good effect.
Well-built, easy to use, only lacks a graphloc back.

Does anyone have an email address for Dominique Stroobant? I had
communicated via his son Ishmael's hotmail account years ago but would
like to get in touch with him again. His 17mm pinhole for Leica thread
mount is still my most beloved pinhole, especially for hand-held work.
Thanks,

Howard Wells
http://home.earthlink.net/~sandwell/

Guillermo wrote:
 
 - Original Message -
 From: Gregg Kemp gregg.kemp@???
 
  Guillermo, I don't remember ever seeing your correction formula before.
 Is
  that theoretical, or have you tested it?
 
 Theoretical, Gregg, as I haven't done any close up work myself.
 
 For those (few) people interested in were that correction factor comes from,
 here it is:
 
 **
 Pinhole is in most ways, not different than glass lens photography.
 
 The lens conjugate equation is:
 
 1 / F = 1 / I + 1 / O
 
 where I = distance pinhole to Image plane;  F = Focal length  and   O =
 distance pinhole to Object being photographed.
 
 We can simplify that to:   F = I x O / I + O
 
 When the Object being photographed is at infinity ( O = infinity ):
 
 I + O = O
 
 therefore the formula  F = I x O / I + O  becomes:
 
 F = I x O / O  and that becomes
 
 F = I
 
 In other words, when the Object is far away (more than 10 times the distance
 pinhole to film, in practical terms), the Focal length of the camera is
 equal to the distance pinhole to film plane.
 
 Now, when the Object being photographed is close to the pinhole lens (less
 than 10 times the distance pinhole to film, in practical terms), the Focal
 length of the camera is given by (as I stated above):
 
 F = I x O / I + O
 
 For close up work, then, F has to be substituted (in any of the formulas
 for optimum pinhole size) by:
 
 I x O / I + O
 
 For instance, the formula I use is:
 
 D = 0.0073 x SQRT( F )
 
 where D = pinhole diameter in inches; F=pinhole camera focal length and SQRT
 stands for square root of
 
 For close up work that formula becomes:
 
 D = 0.0073 x  SQRT( I x O / I + O )
 
 As I said before, F = I  for infinity, therefore I can write the infinity
 formula as
 
 D = 0.0073 x SQRT( I )
 
 Base on that, I can also rewrite the close-up formula as:
 
 D = 0.0073 x  SQRT( I ) x  SQRT ( O / I + O )
 
 There you have the correction factor:
 
 SQRT ( O / I + O )
 
 BTW, there are many formulas for optimum pinhole size but all have within
 them SQRT(F), therefore, the above correction factor should apply fine to
 all of them.
 
 Let's see an example:
 
 Our pinhole camera has a distance pinhole to film  I = 8  and the Object
 being photographed is  O = 12 away from the pinhole, what size of pinhole
 is the optimum to use:
 
 The optimum pinhole size for infinity is:
 
 D = 0.0073 x SQRT ( 8 )
 D = 0.020 (aprox)
 
 Correction factor is: SQRT ( 12 / 8 + 12 )
 Correction factor is: 0.774
 
 Pinhole size for close up work (object 12 from pinhole lens)
 
 D = 0.020 * 0.774
 D = 0.0155
 
 BTW, all the above is nothing but a sort of bellows correction.
 
 For people with mathfobia but that have read this msg up to this point, here
 are some corrections factor based on how many times the camera
 pinhole-film distance the object is away from the pinhole lens:
 
 less than 10 times = correction factor =   0.95
 less than  9 times = correction factor =   0.94
 less than  8 times = correction factor =   0.94
 less than  7 times = correction factor =   0.93
 less than  6 times = correction factor =   0.92
 less than  5 times = correction factor =   0.91
 less than  4 times = correction factor =   0.89
 less than  3 times = correction factor =   0.86
 less than  2 times = correction factor =   0.81
 less than  1 times = correction factor =   0.70
 less than 0.5 times = correction factor = 0.57
 
 Another couple of formulas than may help the original's question poster are:
 
 Magnification   M = I / O
 
 Therefore the Correction factor can also be written as:
 
 Correction factor = SQRT [ 1 / (M+1) ]
 
 So for instance, if she wanted to photograph an object 2 tall  with a
 camera having 8 between pinhole and film and get a magnification of  2X,
 she will need to position the object at a distance:
 
 O = I / M = 8 / 2 = 4
 O = 4 inches
 
 and the pinhole size (diameter) should be:
 
 D = 0.0073 SQRT(8) *  SQRT[ 1 / (2+1)]
 D = 0.012
 
 The image size will be 4 and therefore the minimum format size needed is
 4x5 (portrait) or perhaps -better- 5x7 to allow for some cropping.
 
 Guillermo
 
 ___
 

RE: [pinhole-discussion] f stops

2001-10-30 Thread Gregg Kemp
I wrote to Philip asking if he was having a problem with his mail and if I 
could help.  I haven't gotten a reply, but noticed he continues to send empty 
messages.  

Maybe it's Philip's cat playing with the keyboard(?)

Gregg

 -Original Message-
 From: TSHACK [mailto:tsh...@silver-bayou.com]
 Sent: Tuesday, October 30, 2001 12:54 PM
 To: pinhole-discussion@p at ???
 Subject: Re: [pinhole-discussion] f stops
 
 
 All of Phil's messages are blank.  Just testing to see if 
 mine will be.
 
 
 - Original Message - 
 From: Philip Arny philip.a...@tpl.org
 To: pinhole-discussion@p at ???
 Sent: Tuesday, October 30, 2001 7:11 AM
 Subject: Re: [pinhole-discussion] f stops
 
 
  
  ___
  Pinhole-Discussion mailing list
  Pinhole-Discussion@p at ???
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  http://www.???/discussion/
  
 
 
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Re: [pinhole-discussion] f stops

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] f stops

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] f stops

2001-10-30 Thread TSHACK
All of Phil's messages are blank.  Just testing to see if mine will be.


- Original Message - 
From: Philip Arny philip.a...@tpl.org
To: pinhole-discussion@p at ???
Sent: Tuesday, October 30, 2001 7:11 AM
Subject: Re: [pinhole-discussion] f stops


 
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Re: [pinhole-discussion] Zone Plate Focus stringency

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] f stops

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] f stops

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] Ilfochrome

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] Zone Plate Focus stringency

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] f stops

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] f stops

2001-10-30 Thread Philip Arny


Re: [pinhole-discussion] f stops

2001-10-30 Thread Guillermo
 - Original Message -
 From: ragowaring ragowar...@btinternet.com

  Anyway, enough of an introduction; could anyone please tell me how to
  calculate the natural progression of f stops doubling exposure from one
  number to the next, or post a list of these.

They follow a geometric progression that make the f/stops increase by a
factor of square root of 2

Need a more complete explanation?  let me know.

Guillermo






Re: [pinhole-discussion] Zone Plate Focus stringency

2001-10-30 Thread TSHACK
 Just as a point of reference, if you're going for this look

Well, this is my first time attempting something like this.  I suspect they
will all look the same pretty quickly and get boring.  I can't see this one
hanging on the wall very long.  But, I'm usually heavy into composition, so
its nice to have something that took off on its own.  I'm trying to figure
out how to incorporate a mirror into the image plane to get the image into a
mirror-image Rorschach sort of format.

 you can also get it with a Lomo LC1 - it's a 35mm, with
 a lens with pinhole-like falloff, and it has an exposure meter
 that will keep the shutter open until it thinks it's received

I just ordered a couple of fully manual Lomos from Free Style Camera.  I'll
see what it takes to convert those.  $12 each, so not a huge investment.  I
did a search for the LC-1 online, but kept getting the LC-A.  Is that the
same?  Looks like the one Free Style sells for $149.

 enough light - I've had it stay open 5 minutes.  I have photos
 from halloween in Greenwich Village a few years ago that
 look very much like this one.

I would suspect there is not much variability between photos taken while
driving in traffic at night. ;-)

Thanks for the info.

Dwight




Re: [pinhole-discussion] Ilfochrome

2001-10-30 Thread Bill Erickson
Thanks for the help. I got chemistry from calumet.
- Original Message -
From: Andy Schmitt aschm...@warwick.net
To: pinhole-discussion@p at ???
Sent: Monday, October 29, 2001 3:55 PM
Subject: RE: [pinhole-discussion] Ilfochrome


 Dover Photo in Dover NJ has some stocks  can get it for youit isn't
 cheap...
 be careful of very out of date chemistry. We had a Ilfochrome course at PV
 this year that developed issues when we tried to use up some
chemistrywe
 bought new ( lost $$$ on the course).
 If you want I can check with them on stocks/price...contact me @
 aschm...@aandy.org
 good luck...it's a BEAUTIFUL process...
 andy

 -Original Message-
 From: pinhole-discussion-admin@p at ???
 [mailto:pinhole-discussion-admin@p at ???]On Behalf Of
 b2myo...@aol.com
 Sent: Sunday, October 28, 2001 7:52 AM
 To: pinhole-discussion@p at ???
 Subject: Re: [pinhole-discussion] Ilfochrome



 In a message dated 10/27/01 6:38:22 PM, erick...@hickorytech.net writes:

   I can't seem to find the processing chemicals for ilfochrome in any
sort
 of volumes practical for 'wet lab' home processing. It looks like the
 chemicals are only packaged in larger quantities designed for roller
 processers. Anybody with more information?

 I have a package of 2 one litre bottles (little plastic jars, A, B and C)
of
 Ilfochrome chemistry that I purchased from B  H some time ago...maybe a
 year
 or so. I would guess they still have it but not sure about the shipping
 issue. Let me know if you want me to give them a call to find out if they
 ship towhere are you?

 leezy

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Re: [pinhole-discussion] f stops

2001-10-30 Thread Bill Erickson
Each succeeding fstop is simply the diameter of the aperture divided into
the distance from pinhole to film. The specific numbers are traditional and
represent a set of diameters that yield aperture areas that are double or
half the adjacent one.
- Original Message -
From: ragowaring ragowar...@btinternet.com
To: Pinhole-Discussion@p at ???
Sent: Monday, October 29, 2001 3:57 PM
Subject: [pinhole-discussion] f stops


 Hello Everyone

 I have been following your conversations and have found them very
 interesting.   I am relatively new to pinhole, about two years now since I
 first saw what was going on the web.  I am a painter and find that
 photography makes an interesting a refreshing adjunct to my work.  Pinhole
 photography is a wonderful way to make images and use your imagination.

 Anyway, enough of an introduction; could anyone please tell me how to
 calculate the natural progression of f stops doubling exposure from one
 number to the next, or post a list of these.  I once saw a list on the web
 and have never been able to find it again.  I think you will all know what
I
 mean  5.6, 8, 11, 16, 22, 32 etc up to 1000 or whatever.

 I would find this immensely helpful when calculating exposures and
designing
 cameras.

 Alexis





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Re: [pinhole-discussion] Zone Plate Focus stringency

2001-10-30 Thread Gregory Parkinson

Just as a point of reference, if you're going for this look
you can also get it with a Lomo LC1 - it's a 35mm, with
a lens with pinhole-like falloff, and it has an exposure meter
that will keep the shutter open until it thinks it's received
enough light - I've had it stay open 5 minutes.  I have photos
from halloween in Greenwich Village a few years ago that
look very much like this one.

At 4:52 PM -0800 10/29/01, TSHACK wrote:

- Original Message -
From: Chris Peregoy pere...@gl.umbc.edu
To: pinhole-discussion@p at ???
Sent: Monday, October 29, 2001 4:19 PM
Subject: Re: [pinhole-discussion] Zone Plate Focus stringency

[...]





OK, I just got back a test roll from my hacked TLR zone plate camera.

This is the only one worth reporting on.  Its taken in traffic at night, but
I flipped the image because it works better like that.  Unfortunately, this
doesn't really showcase the zoneplate qualities, unless its to give the
lights a softer glow.  But it certainly has a lot more life than the other
shots on the roll.

http://groups.yahoo.com/group/pinholegallery/files/DSZP/zpdashboard.jpg

Focal length, 90mm, ASA 100, exposure 4 blocks at 25mph.

I'm about to build a rig to use as a mount for the cameras that will fit in
my moonroof opening and allow me to also reach up and trigger the shutter
open and closed.


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