Re: [photo-3d] Camera separation in stereo photography

[Brian Reynolds <reynolds@xxxxxxxxx>]

Dr. George A. Themelis wrote:
> In the MF list recently, one member, new to stereo
> photography, was wondering about the optimum stereo
> base and he shot a lot of pairs with mixed results
> (apparently, there was some problem with mounting
> that caused complications).  A lot of helpful
> discussions and formulas and spreadsheets were discussed
> in an effort to help this guy.  My approach to this
> would have been different.  I would say to the beginner:
> "What is the spacing of your eyes? 65mm?  OK, then
> use this as your stereo base".  If you clear objects
> within 7-10 feet from your camera, you should end
> up with perfectly acceptable stereo pictures and that's
> a good way to get started.
> 

While I agree that starting off with a camera separation of 65mm is a
good way to get started, in the case in question the cameras being
used (Mamiya 7 MF rangefinders) could not be placed that close
together.  The person who had the problem (I'm really bad with names)
had already done slide bar pairs with these cameras using 65mm
separation and gotten good results.  Based on what transpired on the
list, the major problem he was having with the twinned cameras was
mounting the pairs, not figuring out the camera spacing.
Unfortunately as a beginner with no one nearby to compare mounted
pairs with he couldn't differentiate between camera separation
problems and poor mounting.  When another list member was able to get
his actual mounted pairs the mounting problem became evident.

There is no general optimum camera separation.  It depends on what the
photographer wants to do with the image, and what equipment is
available.  My Lubitel images are all shot with separation more than
65mm because the cameras can't be placed any closer.  My Sputniks
images are all shot at 65mm because the camera isn't adjustable.  I
like to see depth in my stereo images so I use the Sputnik when things
are close and a slide bar when they are far away so that I can
exaggerate the depth.

Most of the time I just guess at camera separation.  I like playing
with the formulas, and occasionally precompute the separation, but
it's a pain to do it in the field.  Now that I have access to a good
color postscript printer at work I may go back and make a circular
camera separation calculator like the one I use for pinhole exposures.
If I do, I'll start paying attention to my separation more carefully.

-- 
Brian Reynolds                  | "Dee Dee!  Don't touch that button!"
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