Stereoscopy and Pinhole cameras.

Dear list members,

It came to my mind the thought of doing a stereoscopic pinhole

camera, using 4x5 negs, for later contact printing to cyano,

saltprint, or VDB.

I´d like to be able to do stereos with the standard size of the old

stereo views (mounted in 18cmx10cm I think cardboards), to be able

to use them in the old "viewers" (sp?).

I´m building the camera, and some thoughts came to my mind. I woun´t

be able to do the same size of the standard old stereos, as they are

something like 7x8cm each view. As I´ll be using 4x5 negs, the

images will be 10cm x 6cm.

Did someone ever try this experiment?. Is there any problem I may be

aware of before finishing the camera?

I´ll do the pinholes at 6cm from each other. What distance should I

use when "focusing" closer?. Does this rule apply to pinhole anyway?.

 

Thanks for your comments and advices!!

 

Agustin

From my understanding, stereo lenses are set at the average interpupilary distance, and are fixed. The stereo effect is most pronounced at close distances, exaggerated in close-ups, and minimal at greater distances. Stereo stills of static scenes can be taken with a single camera by simply taking a shot, then moving the camera laterally the proper distance and taking another shot. There are many sites and books devoted to pinhole photography that go into ALL aspects it.

Seems to me that you are going to have a problem getting two pinholes at precisely the same size for equal exposure times. The precision needed at that size is more than I can achieve but maybe those laser cut pinholes you can buy would be good enough. The shift camera method Art mentioned has the drawback of things moving between each exposure but with a pinhole you are already dealing with long exposures so I would go that way.

 

An old article I have says 2.75" seperation for 8-9 feet and further. Use the "Rule of 40" for closer which says divide distance by 40 to get lens seperation. 5 feet or 60"/40 = 1.5" lens seperation. Never tried the formula myself but it was given by Rudy Bender in "Darkroom Photography" 11-83

 

How about a pair of Holgas? They would give much the same look.

Thanks Bob and Art for your suggestions!.

I´m planning to make some tests with the cardboard camera I made, and if I get good results, I´ll make it in wood. I got the size of the pinholes with a formula. They will be small 0,35mm pinholes.

As soon as I make tests I´ll post them here :).

 

Thanks once again.

 

Sincerely,

"They will be small 0,35mm pinholes."

 

As opposed to LARGE 0,35mm pinholes?

 

Use separate shutters to allow you to calibrate time differences between the two pinholes.

 

tim in san jose

Agustin, I'll weigh in on this one only because I've done a bit of pinhole work, but no stereo imaging.

 

Its difficult to make two homemade pinhole apertures with near-identical diameters. The obvious problems caused by disimilar pinholes are exposure issues; the less obvious are differences in softness of the images - though I'm not sure how the later would effect stereo imaging, per se. I'll violate my own do-it-yourself ethic here and recommend commercially made laser-drilled pinholes (one caveat: I haven't heard of these being tested for uniformity between samples, so I'm just assuming they're better than homemade).

 

One homemade alternative is to fashion the front of the camera so that the SAME pinhole aperture can be used, one at a time, for both exposures. This, of course, implies static subject matter.

 

Regarding close-focussing, if you intend on frequently getting REALLY close to the subject, I'd recommend a pinhole diameter slightly smaller than that recommended by the Raleigh criteria, which I feel is optimized for subject matter at infinity. While I don't have the formula in front of me, its easy to find on pinhole websites. It basically relates optimal pinhole diameter with the working focal length of your camera, for an assumed wavelength of light.

 

Finally, I'd also be concerned about registration throughout the process. Perhaps you can fit both images on the same sheet of film, or use 5x7 film. This would guarantee that the registration that the pinholes saw is the same as what the viewer sees.

 

It would be nice to see some stereo pairs posted on this site for our enjoyment. Good luck.

I've made a stereo 5x7 pinhole camera that is surprisingly sharp (at least when making van dyke brownprints on a rag paper). As others have indicated the tricky part is getting the pinholes the same size for equal exposures. Mine are pretty close although I'll probably adjust one slightly before the next use. I have a large, front-mounted, 8 1/2" removable Packard shutter that opens to expose through both pinholes simultaneously. An internal septum prevents exposures from overlapping. The camera body is made out of black foam core with a 5x7 back from an old Seneca view camera. The camera produces two vertical images approximately 3 1/4" x 4 3/4" on a single sheet of 5x7 film oriented horizontally in the camera. I found a nifty rabbet (sp?) cutter for foam core at a local art shop which makes the camera construction a bit sturdier and neat. It also uses epoxied 1/4 -20 T-nuts from the hardware store for tripod sockets.

 

I seem to recall the standard interocular distance for separating the pinholes is 62mm. That's a memory from long ago related to a college course I took involving interpreting stereo aerial photographs and mapping. In that course I also learned to view stereopairs without using a viewer. I once saw directions on how to do this on some online pinhole photography site. Googling might turn up the reference to it.

 

It's a fun thing.

 

Joe

Thanks guys for your advices!

I´m working hard on a project right now. Next week, I´ll have the free time I need to test the stereo camera I made.

 

I´ll post results here.

 

sincerely