T3D Re: Panum's limit

[Peter Homer <P.J.Homer@xxxxxxxxxxxxx>]

>At 9:31 AM -0700 2/4/98, john bercovitz wrote:
>>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.

I have a photocopy from a book on pschology refering to the "Panum phenomena"
I an not sure whether this is the same as John Bercovitz was refering to as
there are some differences ." On a homogeneous background Panum (1858)
presented  a vertical line to one eye and two vertical lines to the other.
He found that if one of the double vertical lines is fused with the single
line in binocular presentation the subject percieves the unmatched line to
be further away than the fused line.(As exploited in stereo mounting grids
such as the one manafactured by Reel 3D to set the near and far points in a
slide?).This depth effect was found to occur only when the distances
between the double lines was very small(aproximately 6' of arc) ". Beyond
that is refered to as Panums limiting case.
 Julez (1968) had subjects look at one line with the right eye and another
with the left ."The two lines were seen as a single fused line when they
were registered within 6' of arc. If any greater two lines were seen. But
Julez found that once fusion occured the amount of area seperating the two
lines could be increased markedly without loss of fusion .In fact distances
of over 2 degrees (120' of arc) could be reached before fusion was lost.
Reducing the distance between the lines after loss of fusion did not
produce a single image untill Panums limits were reached again".
  There is a big difference between 10 or 20 and 6 minutes for Panums limit
but the work by Julez implies that 2 degrees would be possible provided
fusion was achieved at 6' first.      P.J.Homer



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