Re: [photo-3d] Cardboard cutout effect?

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

>The pictures in question were taken with 60mm separation and with a  
>minimum distance from camera to subject of 6 feet.

What about the focal length of the recording lens?
The focal length of the viewing lens?  These two
are very important parameters, IMO.  

"Cardboard cutout effect" is the feeling that we
get when viewing stereo images, that instead of
real objects (especially people) we are looking
at cardboard cutouts, i.e. while we can see different
objects being at different depth levels, we do not 
see depth within the objects.

Several factors contribute to the cardboard cutout 
effect:

1. Long focal length of recording lens(es) (especially
if accompanied by a small stereo base).  A good live
demonstration of this is looking through binoculars (high
magnification, short stereo base).

2. Short focal length of viewing lens (in relation
to the focal length of the recording lens).  This
leads to what is known as "squash", a compression
in the third dimension.  Also, reduced resolution
or increased aberrations of the viewing medium.

3. Composition (as mentioned by Eddie).  The worse
situation is to have something in the foreground,
followed by the distant background, with no graduated 
depth in-between.

4. Unfamiliarity with stereo imaging and comparison
with reality.  This is a pure psychological/physiological
effect.  In real life we move around and motion parallax
contributes greatly to the sense of depth.  When viewing
a stereo image there is no motion parallax.  Furthermore,
we are comparing the image with reality.  The result is
a wax museum impression or, if combined with factors
1-3 above, a cardboard cutout feeling.  This explains
why comments about cardboard cutout effects come mainly
from beginners and not seasoned stereo photographers.
I think that complains for cardboard cutout impressions
are a sign of healthy stereoscopic vision/experience
by beginners.

I remember my very first Stereo Realist picture.
I asked my wife to pose in front of our apartment
building.  She stood looking straight ahead at
about 7 feet from the Realist.  I lowered the
camera angle and took a picture.  When I looked at
it with the Radex viewer I experienced a very
strong cardboard cutout effect.  This is the result
of factors 3 and 4 mainly.  Had I asked my wife
to turn her side to me, or had I used a higher
angle (which will have included the graduated
depth of the pavement) this effect would have
been minimized.  Also, it was my very first stereo 
picture.

George Themelis