Re: Nimslo Prints vs Slides

[bercov@xxxxxxxxxxx (John Bercovitz)]

>> So you need to enlarge only the middle of the Nimslo to 3" 
>> height to make the stereo card pair.  If you ignore this, 
>> you'll get a lot more stretch than you get viewing Realist
>> slides in a red button viewer.

> But don't forget the itty bitty baseline (well, smaller than a
> Realist, anyway).  I can't imagine stretch would be too much of
> a problem, perceptually speaking...

Ah, but apparent size changes due to changes in camera baseline are 
independent of apparent size changes due to changes in perspective 
(changes in distance of viewpoint from image), though these changes 
multiply.  

Changing baseline changes all three dimensions.  

Changing perspective only changes the third or depth dimension.  

To look at the present example, let's say we have only half the 
camera baseline we should have but we also view from twice the 
distance we should.  First, halving the camera baseline doubles 
the apparent size of all three dimensions (hypostereo).  Second, 
doubling the viewing distance doubles only the depth dimension.  
The net result is that height and width are doubled and the depth  
is quadrupled.

To see the geometry, go to:
 ftp://bobcat.etsu.edu/pub/photo/photo-3d/technical/
and get orthomag.gif and orthosep.gif.  They're little 10K pictures,
but they're a lot better than having me write about it.  8-)

John B


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