[tech-3d] Re: Stereo Base Calculation With a $20.00 Handheld

["Abram Klooswyk" <abram.klooswyk@xxxxxx>]

Boris wrote:
> I have a question.  Why does a viewing device focal length (i.e. a 
> viewing geometry) even come into play?  On film deviation is the 
> product simply of camera optics, stereobase, and near and far
> point. 
> Why the viewer F.L.?
> Granted, the viewer optics affect the perceived depth, but it 
> certainly does not change OFD.
> (And for my application, in shooting for anaglyphs, there is no 
> viewer F.L. There may be a print size, and a viewer's naked eye 
> distance to print - that would form the equivalent to a viewer's 
> focal length.  But to shoot for a specific size anaglyph print, 
> and therein a specific deviation on paper, I want to predict and 
> set up a shot simply for a particular deviation on film.  
> Viewer optics are not otherwise considered.)

Boris, 
Since viewing is the aim of making stereopictures, wouldn't you 
agree that considering the final viewing situation should be done
before making the pictures?
In the text with the so-called Bercovitz-Spicer equation is said
that viewer focal length should always match camera focal length
("orthostereoscopy"), but that obviously leads into absurdities
when you consider very long camera focal length. 
(I have said this before. Where is John Bercovitz anyway?)

As a general remark: "camera" focal length as well as "viewer"
focal length should be taken in a broader sense, 
"camera" including virtual camera in computer graphics, 
electronic microscopes, pinhole camera, stereo drawing,
and "viewer" including size/distance relations in viewing
anaglyphs, computer screens, projection screens, freeviewing.

Abram Klooswyk


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