T3D Re: Panum's limit

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

 John Bercovitz wrote in reply to my post
>
>> They seem to me to be implying than 6' is the upper end for
>> stereo separation because after that the image doubles, unless
>> the separation is started at 6' and then increased up 120' or over.
>
>I am conflicted by this statement.  Are you saying you lose stereo
>above 6' or you start to see stereo above 6'?  If you lose it, how
>can you go to 120'?  Aha!  Is it like this?:

They are saying it not me and you seem to have answered your question
yourself based on what I said below.

>"They seem to me to be implying than 6' is the upper end for stereo
>separation because when disparities greater than that are presented,
>the image is seen doubled, unless the separation is started below 6'
>after which the sepration can actually be slowly increased up to 120'
>or more.

 What I think they are saying is that if you go straight in cold over 6'
you dont get stereo fusion but if you start at 6' or less then increase it
while viewing you can maintain fusion up to 120' or a little over.


>So this implies that when we view a stereo pair, we start by locating
>parallactic disparities under 6' and then we build on that right on
>up to 120' at which point things start to fall apart.  At least they
>do in stereo pairs.  In real life, we seem to be able to get around this.

Actualy I think I had assumed because the vertical lines on the stereo
mounting gauges seem to make use of the Panum phenomena that they must be
at 6' or less it was you yourself that pointed out in an earlier post that
they are at about 2 degrees "with the normal viewing lenses". Which
according to Julez is about the limit for fusion even if increased gradualy
from 6'. I will take your word for the 2 degres figure I have not measured
the angle myself or even shure how to do it I usualy think of the
seperation on these gauges in terms of the distance in millimetres that
they are marked with.
 It does seem to contradict Panums findings that his phenomena apears to
work with these 2 degree seperated lines. You mentioned the possible affect
of the lenses I use a Casssela viewer with adjustable interocular now but
then I started using a simple viewer with no adjustment. The lines still
fused correctly . Perhaps we fuse the near point line first then the far
point but there is still no continuos transition with a gauge alone that
Julez describes as neccessary. With an actual stereo pair its easier to
understand as we probably start with the foreground and move  to the far
point through the scene.

>> I realise this seems to be at odds with the technique of using
>> turntables to take stereo pairs
>
>I think we're still OK here.  The 2 degree angle I am talking about is
>the angular subtense of the on-film parallactic disparity and I don't
>believe (though I haven't checked) this has a 1:1 relationship with
>turntable angle.

Thanks for clearing that up for me I am going to be on holiday now from
tomorrow 9th April to the 16th I dont usualy bother to cancel tech-3d as
the traffic is fairly low (although quite busy at the moment) but I will be
able to reply to posts untill I get back.

     see you then P.J.Homer




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