P3D Re: Curious Deep Math Tale

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Michael Georgoff noticed something curious:

>It appears that stereo base is dependent on f-stop.  That is all. 
>Stereo base in mm = 1200/f-stop.

You have just discovered that the formulas for the Depth of Field
and the Stereoscopic Deviation are very similar.  This is something
that I discovered myself while "playing" with formulas (as you did)
and then was happy to confirm that others knew (for example, see
Lenny Lipton's "Foundations of the Stereoscopic Cinema).  

Also, Charles Piper had taken advantage of these simiarities and 
worked out a method where you use your Depth of Field Scale on your 
stereo camera, to determine the stereo depth range.  For example,
in Intallment #1 of his Technical Page (a "must have" book, BTW)
Piper writes:

"Make sure that the near and far points will fit between the f/5.6
marks (he means the marks of the DOF scale).  For instance, you 
can take a projectable picture from 7 ft to INF, or from 5 ft to
20 ft."

So, he is using the DOF scale as a depth range scale.  He picks
f/5.6 as the aperture to give the maximum amount of deviation for
a projectable stereo.  You are seeing the same thing.

I have brought this "curiocity" up and discussed it a few times in 
photo-3d in the past (maybe 2 years ago was the last time).  If you 
do an archive search, look for depth range, etc.

Hope this helps (or puts you in the right track),

George Themelis





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