P3D Re: wide, normal, and long lenses and views

[koganlee@xxxxxxxxxxxxx]

"Challenging question:  Would you say that our definitions of normal,
wide angle and telephoto lenses also depend on viewing conditions?

George Themelis"

        George, of course, already knows the answer to this question. The 
answer is that what makes an image normal, wide, or long depends solely on 
the viewing conditions. In 2D photography if you enlarge a wide angle image, 
for example, 8 times to make an 8x12 image and view the image from 8 times 
the focal length of the taking lens (say a 24mm (1 inch) x 8 = 8 inches) 
then you are at (what is know as in 2D photography as) the "proper viewing 
position" (same as "ortho" in stereo) and you have what is in effect a 
normal view. If, on the other hand, you were to view the image from 16 
inches (as one would be likely to do), then it would be a wide angle view.
        Conversely, with a long lens, if you look at it from farther back than 
you normally would (let's say it was a 100mm lens and you viewed the 8x10 
from 32") then it would also be a normal view, and the perspective would 
look perfectly normal. However, if you viewed it from 16" then it would be a 
"long" view and the perspective would be as we have come to expect a long 
lens to give.
        In addition, a normal view is only normal is it is looked at from the 
normal viewing position. If you are closer or farther from the image it then 
becomes a wide or long view.

David Lee


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