[pinhole-discussion] zone plate
Hi, 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
- Original Message - From: Guillermo pen...@rogers.com 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
[pinhole-discussion] nitric acid
Dear Dennis, Just forget the nitric acid. This is so strong it fumes when you take the lid off the bottle and it is hard to get because it is so dangerous. If you do find some,, dilute it by adding it to water (it is heavy and will sink at first), not adding water to it, as the boil up will be dangerous. Also, do it outside with plenty of ventilation, and near water so you can wash the outside of the bottles off after putting the lids back on and can wash up any spills. IT IS DANGEROUS. Jean
Re: [pinhole-discussion] Zone plates for a body cap
- Original Message - From: Beaker mbea...@mac.com Guillermo- how do you figure out the aperture of a zone plate? Mr. Pinhole mentions this formula: radius = sqrt(wavelength * 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
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? I gave up on filters altogether, and just started shooting color film. This allows me to adjust contrast and convert to greyscale in PHotoshop. You have an astounding amount of contrast control- much better than filters could ever give. At least, that is my experience. This site appears to talk about it: http://www.bythom.com/bandw.htm
Re: [pinhole-discussion] using filters
- Original Message - From: Jeremy Jeffs jeremy.je...@virgin.net 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] using filters
Jeremy, What I do is I hold the filter with my had in front of the pinhole and keep moving through out the exposure. That way the dust is not in one place long enough to record on the film. James On Saturday, October 26, 2002, at 12:10 AM, Jeremy Jeffs wrote: 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? thanks, Jeremy. ___ 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/ James Kellar Co-manager of the Pinhole Discussion List http://www.???/discussion/ pinh...@jameskellar.com
[pinhole-discussion] using filters
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? thanks, Jeremy.
Re: [pinhole-discussion] Zone plates for a body cap
Didn't finish reading all the posts, I would be interested in a 7 ring and a 21 ring for 50 mm, say $10 each (negotiable of course), plus maybe one in the 75mm range for starters. Flexible, again let me know what you want because this sounds like a great way to get into zone for not a ton of money. Thanks again, Thom tjmi...@ix.netcom.com - Original Message - From: Beaker mbea...@mac.com To: pinhole-discussion@p at ??? Sent: Thursday, October 24, 2002 11:24 PM Subject: Re: [pinhole-discussion] Zone plates for a body cap On Thursday, October 24, 2002, at 10:28 PM, Guillermo wrote: - Original Message - From: Beaker mbea...@mac.com 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 All Good points- thanks! I was tinkering around with Mr. Pinhole's zone plate generator, and had already made up smallish group of 43 mm, 7 ring (I think) zone plates. That is what I had in mind with the first post. If there is any interest, I could just as well make up a group of custom zone plates. Guillermo- how do you figure out the aperture of a zone plate? Mr. Pinhole mentions this formula: radius = sqrt(wavelength * focallength * ring). I was guessing that this would give a good number to start with. Is this a good guess? 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! ___ 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] Pinhole of partial eclipse
Do you have a web address for this search? I have partial eclipse leaf pinhole shadow images. Richard Heather - Original Message - From: gregg b. mc neill gbmcne...@hotmail.com To: Pinhole-Discussion@p at ??? Sent: Thursday, October 24, 2002 10:43 AM Subject: [pinhole-discussion] Pinhole of partial eclipse hey pinholers, this is a post from the Cinematography mailing list I belong to. I thought some of you might be interested in this, particulaly in the submission of a photograph to be (potentially) included in this VERY well respected magazine. gb mcneill Very interesting, because I am looking for a particular photograph of a partial eclipse to illustrate a piece I have written for the 'From my Library' series I have been writing for The American Cinematographer Magazine. For those who may have seen the first one in the September issue (there are others upcoming in the November and January issues) the idea is to dip into old books that I have in my library and do 'book reviews of 100ish year old film books For a forthcoming piece on the History of Projection I start with a quote from Volume 1, No. 1 of the Journal of what is now the Royal Television Society, published in Sept 1938. (it is one of the real treasures of my library) The very first major article (believe it or not) is a history of optical projection which starts off (if the ACM will excuse me leaking a preview) In Volume 1, No. 1 of the Journal of the Television Society, published in September 1928, (the first ever monthly journal devoted to television) the first major article, by Professor Cheshire of the Imperial College, London, was devoted to Optical Projection: It began with the question: Why is it that during an eclipse of the sun the patches of light, which are found on the ground beneath a plane tree, and which are formed by rays which have passed through the spaces between the leaves, take the shape of the eclipsed sun? ... In these words did Aristotle, about 350 B. C. propound his famous problem concerning the optical projection of pictures. Nearly 2000 years elapsed before a satisfactory solution of this problem was given The answer, as we now know, was pinhole projection caused by gaps between leaves. Anyway, in the TV Journal there is an illustration of crescent shaped blobs of light beneath a tree taken on Bombay many years ago. Regrettably the quality if the image is not good enough to reproduce in a 2003 edition of the ACM so I have had to make do with a picture of every-day oval shape blobs I took beneath a tree in Hyde Park. So, I wonder if anyone in Australia who is in the eclipse zone on December 4th would be kind enough to take a copyright-free photograph for me, not of the eclipse but of the pinhole image of it on the street below a tree ... which is the way ancient astronomers used to study eclipses. If I get it in time I would like to use it as an illustration (with credit, of course!). For anyone interested in the subject of pinhole projection, during my researches I came across an interesting fairly new book on the subject, 'Pinhole Photography' by Eric Brenner, Published by Focal Press, 1999, ISBN 0-240-80350-7'. I thoroughly recommend it if for no other reason that it has in it one of the most interesting bits of useless information I have come across for a long time ... How it was that Pope Gregory XIII in 1580 was convinced that the calendar was ten days out of sync with the sun? ... 'Tell me more' do I hear you say? But that, dear CMLers is for another night (or subject heading?) Sincerely David Samuelson _ Get faster connections -- switch to MSN Internet Access! http://resourcecenter.msn.com/access/plans/default.asp ___ 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] Zone plates for a body cap
On Thursday, October 24, 2002, at 10:28 PM, Guillermo wrote: - Original Message - From: Beaker mbea...@mac.com 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 All Good points- thanks! I was tinkering around with Mr. Pinhole's zone plate generator, and had already made up smallish group of 43 mm, 7 ring (I think) zone plates. That is what I had in mind with the first post. If there is any interest, I could just as well make up a group of custom zone plates. Guillermo- how do you figure out the aperture of a zone plate? Mr. Pinhole mentions this formula: radius = sqrt(wavelength * focallength * ring). I was guessing that this would give a good number to start with. Is this a good guess? 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!
