Re: requirements for a new camera

[Richard Twichell <73163.3423@xxxxxxxxxxxxxx>]

John B. writes:
> I would put the lenses 
>67 mm on center and the film gates 69.25 mm on center for a 1.5 m 
>built-in window ...

Piper writes in Installment #72, The Technical Page, "For the two most 
common stereo cameras, the Realist and the Kodak, the inward displacement 
of the lenses is:  Realist:  1.55mm, Kodak:  1.17mm, corresponding to a 
"basic camera window" at 62" and 83" respectively."  In a chart labelled 
"Mask Aperture Dimensions and Window Location" Piper shows that  due to 
differences in their "official" masks, a Realist slide in a Realist mask 
windows at 68", and a Kodak slide in a Kodak mask windows at 64".  However, 
a Kodak slide in a Realist mask windows at 92"!

A question:  with John B.'s suggested displacement of 2.25mm, would there 
be visible keystone distortion due to this offset?  An offset lens is, is 
it not, a PC lens on it's side?  And, would not this amount of offset 
display the type of keystone distortion which is sometimes seen, and 
objected to, in prismatic C/U lenses?

Or does the longer focal length suggested by JB compensate for this?  (At 
this point innumeracy raises its ugly head)  I am not sure if Piper means 
displacement for each lens off center, or the total of both.

Dick Twichell


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End of PHOTO-3D Digest 1233
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