T3D Panum's limit

[john bercovitz <bercov@xxxxxxxxxxx>]

Panum's limit is around 10 or 20 minutes of arc per something 
Jim C wrote a few years back.  Beyond that, you get retinal 
rivalry due to parallax.  The 1 in 30 rule (on-film deviation 
shouldn't exceed 1/30th of the focal length) works out to about 
2 degrees.  This is a long way from 20 minutes.  I wonder if 1 
in 30 isn't an upper limit to a sort of "Panum's range" and 20 
minutes is the lower limit.  I'll bet when they tested and got 
the 20 minutes figure, they were using the starkest targets they 
could find.  No diffuse stuff, no stuff that is more typical of 
the average scene, which is bounded by a 2 degree limit.

John B


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