[photo-3d] Lenticular depth resolution (was: Camera separation ...)

[Abram Klooswyk <abram.klooswyk@xxxxxx>]

This is just a minor point in the discussion between don lopp 
and Greg Erker, which I fear to enter because it generates so 
much quoted postings :-)

Greg Erker (6 Jul 2000):

>Lower resolution formats like lenticulars need more OFD or 
>more physical separation between objects to be able to 
>discern depth. If you try to take a smooth depth shot and 
>view it on a 3x4" lenticular photo you will be very 
>disappointed by the lack of depth. A row of flowers at 6', a 
>person at 10' and a far away scene (at infinity) will give a 
>much more satisfying lenticular (I'm sure an 8x10 lent would 
>work much better).

Resolution in the general photography sense is measured in 
line pairs per inch (or mm) on the film. 
With higher on film resolution (physical resolution) mostly 
also a higher stereoscopic depth resolution (perceptual 
resolution) is achieved, you can see more "steps in depth" 
(in the past I have written on this subject in "Stereoscopy").

However, lenticulars are different. The depth in lenticulars 
primarily depends on the size of the lenslets. The lenslets 
are small cylindric lenses, but they are _lenses_, to which 
optical laws apply. 

In a theoretical optical research Takanori Okoshi of Tokyo 
University has demonstrated that the best _possible_ depth 
resolution of lenticular systems generally lays between only 
3 and 10 "steps in depth" !
(He uses a slightly different terminology, see his book 
"Three-Dimensional Imaging Techniques", New York 1976, p.95)

It is likely that classical twin-view stereoslides can show 
some 40 steps in depth in projection, more in viewers, and
MF in handviewing probably reaches at least double that
figure.

Nimslo 3D prints have a fine lenticular grid, large "8x10 
lent"s mostly a much coarser, and this governs their depth 
resolution, not the resolution of the film used.
Improving their depth resolution is not possible beyond the 
limit set by the optical laws to which the lenslets obey.

Abram Klooswyk