Re: [photo-3d] Re: Newbie question-near point distance

["Dr. George A. Themelis" <drt-3d@xxxxxxx>]

Hi Linda... It seems that you have discovered the PePax
principle for yourself :)

What I have found is that increasing the stereo base tends
to neutralize the cardboard cutout effect when using long
lenses.  

After showing some of my wild zoo animal pictures around
(taken with 135mm lenses) people usually ask how did I
get that close to the wild animal.  They are mislead to
believe that the pictures were taken with a Realist.  So I
fooled them!  Long lenses and larger base looks like
shorter lenses and shorter base.  McKay was right after
all!  But not 100% right, because....

If you have a very familiar subject (like a portrait) you
can see where this principle fails.  Things closer to the
camera (nose) appear smaller.  Things further from
the camera (ears) appear larger.  Here is why:  By
using long lenses, I fool my viewer into thinking that
I am closer than I really am.  If I were closer, the nose
should be bigger and the ears (being further from me)
smaller.  But because I am really far away, the size
does not change.  Hence they perceive the opposite 
effect (small nose, large ears).

BTW, I have explored the effects of 1) stereo base
(hyper, normal, hypo-stereo), 2) focal length of taking 
lenses, 3) focal length of viewing lenses (squash, stretch)
in a series of Tutorials for the Stereogram, which I offer
for sale.  The Tutorials are illustrated with stereo pairs
of tabletops that I took with a digital camera (psss...
don't tell Marshal! :))  Get your copy at the NSA 
convention!

George



 

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