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

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

don lopp:
>Back to basics 101 -- I believe that the 1:30 rule 
>only applies when using 35 mm lenses Don.

Greg Erker:
>I believe it applies any time the viewing FL matches the 
>taking FL.

I believe Greg is right, for the simple reason that the 1/30 
rule is a _viewing_ constraint, which aims at limiting the 
convergence difference in stereo viewing. 

The difference between looking at at 7 feet (about 2 meters) 
distance and looking at infinity (zero convergence) is about 
two degrees.
(Interpupillary 65 mm divided by distance 1950 mm is 1/30, 
and the tangent of an angle of 2 degrees is also about 1/30). 

>From experience is believed that two degrees is a safe limit
in viewing stereopictures. This holds for any type of stereo
photographs, and also for drawings, computer 3D etc.

It is easy however to give an example were two degrees is too 
much: a person at 7 feet before a distant mountain backdrop.
On the other hand, two degrees is too restricted for e.g. many
macro stereos. "Double depth" will do better.

Abram Klooswyk