Re: Stereo Window - Poll time!

[P3D john bercovitz <bercov@xxxxxxxxxxx>]

John Bercovitz writes:
> Some things to keep in mind during your deliberations.
> Convergence is a weaker depth clue so don't think of the
> eyes as triangulating on something to find its distance
> unless it's very close.  (Extremes of convergence will 
> have an effect.)  The eyes/brain will establish their own 
> infinity from scene context.
 
Larry Berlin writes:
> This comment is interesting. I'm inclined to see convergence 
> as a rather strong clue in stereo images particularly. Perhaps 
> it is because a stereo image is in fact a close object, though 
> signifying a larger scene through relative interpretations? Or 
> is it because I have learned to use convergence to a greater 
> than normal degree? (in which case I urge anyone to develop that 
> greater sensitivity!)
> 
> The fact that the *eye/brain will establish their own infinity 
> from scene context* is the mechanism by which a base for detailed 
> relative triangulation is established. I have always felt that 
> even for persons who haven't developed this sense, that it was 
> there functioning on more subconscious levels. It's the fact of 
> its usually unacknowledged presence that makes it possible to 
> easily develop the sense to a finer degree.
 
I'm not sure I understand precisely what you're saying here, 
Larry.  I'm saying the map is built up by whatever means and 
convergence is a secondary and weaker clue.  I think you're 
saying convergence is the primary clue, the start of the map.  
Have I got that right?  If not, there's no point in reading 
further; let's discuss your thesis first.
 
*************************************************************
 
First, perhaps we stereo nuts are far from noble savages; our
eyes may not be quite right anymore, particularly in the 
area of convergence.  8-)  Be that as it may, I'll tell you what
I see when I freeview pairs in stereo magazines.  You can find
pairs with separation anywhere from 25 mm to 100 mm.  For ref-
erence, I freeview from 400 mm because that's where my glasses 
are set.  When I freeview a pair separated at 25 mm, I see 
infinity lying at infinity, not at 600 mm.  When I freeview a
100 mm pair, I see infinity at infinity, not 800 mm behind my
head.
 
If I crossview a 100 mm pair, I do see some changes, but you 
would have to expect even a weak clue to have some effect when 
that weak clue is screaming that the thing is only 160 mm away.
 
John B
 


------------------------------