P3D Re: slide bar

[fj834@xxxxxxxxxxxxxxxxxxxxx (Dr. George A. Themelis)]

Steve Berezin asked me to elaborate on this:

>Moderate hyperstereos (in the order of a few times the normal 65 mm) 
>in my opinion are pretty much useless.  

I know it sounds very provocative as a statement, but here is my
reasoning:  Our eyes are spaced on the average 65 mm apart.  
There are many situations where we would like to shift the camera
less than 65 mm.  Close-ups, macro stereo, excessive depth in the
scene, etc.  I cannot think of any practical situation where 120 mm
would do it, while 65 mm would not.  Can you?  If the subject is far
away and a hyperstereo is needed, usually this would be quite a few
times the average interocular and not just two. 

In the particular example of the Bogen slide bar, the maximum shift
of this bar is 80 mm.  If someone claims that this is not long enough
and they would like something that goes to, say 150 mm, I would question
how useful the shift from 80 to 150 mm is.  What is it that you are
photographing where 150 mm shift is desirable while 80 mm would not do
it?  If you want to record hyperstereos usually you want to go over
150 mm and a slide bar might not be the best way to shift the camera.
The Bogen slide bar is very compact.  Anything moderate longer would
result in something that trades convenience for questionable usefulness
in my opinion.

George Themelis


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