P3D Depth Range - Part I

["Dr. George A. Themelis" <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

We continue with our mid-week lectures on stereo photography,
courtesy of DrT.

The concept of "depth range" is very important in stereo photography. 
The "depth range" is defined by the distances of the closest and the 
furthest objects from the camera.  Our eyes are very flexible and can 
easily look at things from a few inches from our eyes, to infinity.  
In stereo photography however the depth range must be restricted.   
Why and how much?  To answer this question you must understand the 
concept of "stereoscopic deviation".  There is just no way around it. 
Here it my attempt for a simple explanation:

In a stereo pair the right and left images appear identical but they 
are not.  Foreground objects are shifted with respect to background 
objects by small amounts in the horizontal direction.  These shifts 
are known as stereoscopic deviation and they are responsible for the 
sense of depth when viewing the pair.  

No stereoscopic deviation = no depth.  Too much deviation = too much 
depth.  Too much depth will made the pair hard to fuse and will cause 
problems in projection.  

How much is "too much"?

To be continued... (tomorrow) -- George Themelis



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