ULF Pinhole?greenspun.com : LUSENET : Large format photography : One Thread
Every so often I start drooling over the prospect of shooting ULF, but fortunately I am in no danger of having enough disposable income in the foreseeable future to enable me to purchase a 12x20 and the requisite lens and holders. I was wondering if any of you knowledgeable people have ever tried building a 16x20 pinhole camera? There are lots of pinhole websites, and I found an excellent table at the Penultimate Pinhole Guide cross referencing film to plane distance, optimum pinhole size and f/no., but none of the sites I visited had any information on the image circle a given size pinhole would produce at a given distance. This seems like a cheap way to try ULF using 16x20 paper and a box. Does anyone out there know of a table for pinhole image circles or can give the specs for a 16x20 pinhole camera? Thank you!
-- John Kasaian (firstname.lastname@example.org), February 06, 2002
The actual image circle is somewhat (totally actually) dependent upon the thickness of the material used and the aperture cut (and how cleanly it is cut). Under ideal circumstances you may be looking at an acceptance angle of ~150 degrees. Just remember the Cosine law - things will get darker toward the edges the wider the angle that you use.
-- Wayne DeWitt (email@example.com), February 06, 2002.
I havn't seen any such table either, but judging from most cameras I've seen pictures from (in 4X5"), the shortest "focal length" seems to just shy of 2". For 16X20" that would be some 8". Now, you will probably have severe light falloff and possibly some vignetting as well, apart from the extreme wide-angle effect. Given that 25" is the "normal" focal length for that size, I'd start with a camera 12" deep. with a hole that is some 0.7 mm (slighty smaller than 1/32").
As you've probably already figured out, this camera would just be a box, which you can make as nice (or ugly) as you want, as long as it keeps stray light out. You can spend one hour or one week building it. (It will probably look much nicer in the one-week version.)
The main thing it that you have fun doing it! (People who pass when you take pictures with this beast will have fun looking at you. ;-)
-- Björn Nilsson (firstname.lastname@example.org), February 06, 2002.
John... If you are building your own camera for pinhole why not consider constructing a method to arc the filmplane around the hole... keeping the center & the edges of the filmplane equidistant from the hole. I would think that should produce a type of panoramic camera...??? -Dave
-- Dave Richhart (email@example.com), February 06, 2002.
hi john i am building a 8x20 pinhole camera for pretty much the same reasons you are...
from the research i have done - you can get laser cut pinholes of any minute aperature from pinhole resource or a place called "minute aperature" in wi. the thinner the shim is that the hole is cut into, the better chance of full coverage and the image circle is about 3x the focal lenght. good luck! - john
-- john nanian (firstname.lastname@example.org), February 06, 2002.
Thank you all for the great ideas! I think I'll try Bjorn's specs and I like the idea of an arc to hold the paper/film as Dave suggests.If I have trouble making my own pinhole, I'll contact Pinhole Resource as John suggests. Thank you all!
-- John Kasaian (email@example.com), February 06, 2002.
Could someone tell me how to contact "Minute Aperture" or "Pinhole Resource?"
Could you also suggest some of the best pinhole camera forum sites?
There is a book of Venice which has stricly pinhole images which has sparked my curiosity about the practical use of these cameras.
-- ARMANDO CONTI (BASISAUDIO@CS.COM), February 07, 2002.
Armando and all others
Pinhole resource is at http://www.pinholeresource.com and one of the users that have had his page up for a long time is Jon Grepstad at http://home.online.no/~gjon/ (where you find a pinhole link, with lots of info and links).
-- Björn Nilsson (firstname.lastname@example.org), February 07, 2002.
John, You have already been giving you good suggestions. Risking being redundant, allow me to add this: A flat film plane camera would be affected by the "full" COS^4 law. It is said that "acceptable" fall off (under pinhole imaging standards) is obtained with cameras whose focal length is no more than 3.5 times the diagonal of the film format, BTW, 3.5 times would give you a camera with an angle of view of about 120 degress, equivalent to 12mm lens on a 35mm format camera. If you really dislike fall off, use a focal length no more than 2 times the diagonal, which still would give you a wide angle of view (2 times would give you the equivalent to 21.5mm for 35mm format).
An ARChed film plane is a good way to reduce substancially the fall off, so that is a good suggestion, just wanted to add that if your camera is cylindrical, you would get distortion (something good if that is what you want). If you don't want distortion, make your camera a half cylinder and position the pinhole right in the center of the the half-circle describing your arched film plane.
Making pinholes is not that difficult, the difficulty most people have is in measuring them. A microscope with measuring capabilities is what I use, but also a scanner (flat bed or film scanner) could be used, I wrote a small article (nothing fancy) on how to do that, here is a link to a page that points to it:
-- Guillermo (email@example.com), February 07, 2002.
Thanks for all the advice!I"m getting the thinnest brass shimstock I can find for my pinhole and I've been trying to rig some kind of go no go guage, either that or take it to the local University. I've found that a box of Krispy Kremes on the desk of the right people are an excellent way of tapping the their resources and getting things done(like having a pinhole measured) I think following the directions I've seen on the web---making a dimple and sanding it down until it becomes a hole will be interesting. For a film/paper holder I think I will get some soft metal like brass or aluminium, bend it to form the semicircle and make a channel on each end to keep the paper from slipping. With the paper/film holder and the pinhole finished, I only need to find a box it will fit in to try my "proof of concept" before attempting to build a wood body. Hmmm...I've got some redwood from an old fence thats been replaced...Maybe I could take a picture of a redwood with a redwood camera?? Thank you all!
-- John Kasaian (firstname.lastname@example.org), February 07, 2002.