T3D Re: Panum's limit

[john bercovitz <bercov@xxxxxxxxxxx>]

P.J.Homer wrote:

> 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 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 separation can actually be slowly increased up to 120' 
or more."

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.

> 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.

John B


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End of TECH-3D Digest 289
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