P3D Cardboarding and telephoto lenses

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

>>>Attempting to compensate for cardboarding by extending the stereobase 
>>>will fail, as was discussed on P3D late last year.

I too, believe that this statement is incorrect.  Increasing the 
stereobase will indeed eliminage cardboarding.

>according to Herbert C. McKay.  I quote from his book (below)
>explaining things (I love this book). 

I love McKay and this book too, but this statement is questionable:

>If we maintain a proportional increase between base and magnification, 
>the type of reproduction closely approximates that of orthostereo. 

The question is "how closely"?

In this situation there is a distortion that can be noticeable:  The
objects further away appear larger.  For example, if you take a portrait
with 135 mm lenses and view it with the normal 45-50 mm viewing lenses
then the ears will appear to be disproportionate large, compared to the 
nose (or visa versa).  This makes sense if you think about it.

McKay was a practical man and he believed that if you don't see it, it
is not there.  I was not seeing this distortion untily it was pointed 
to me by Dr. Milligan and then I saw it and found it disturbing.

>>My working definition of "cardboarding" for some time now has been:
>>Lack of stereopsis *within* an object, while stereopsis is present 
>>*between* objects.

Is "stereopsis" the process though which the brain combines the two
images to result in one that has depth, or the experience of depth 
itself?  Even if these two things are the same still I'd rather replace
"stereopsis" with "depth" for the benifit of the "laymen".

But also the definition: "A condition where objects appear as if cut
out of cardboard and lack individual solidity" sounds good too.

-- George Themelis


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