Re: Hyperstereo applications of the 1/30 rule

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Tue, 5 Nov 1996 12:14:23 -0600
>From: "P3D Dr. George A. Themelis" <fj834@xxxxxxxxxxxxxxxxxxxxx>
>Subject: Hyperstereo applications of the 1/30 rule

>The 1/30 and similar rules aim in producing a stereo pair that has a
>certain amount of on-film deviation.  For hyperstereos, the 1/30 rule where
>the closest subject is at 30 times the interocular distance and there is
>also infinity present, will result in the same amount of on-film deviation
>as a regular stereo with the closest object at 7 feet and infinity present.

>If there is no infinity present, you will get less on-film deviation.

I agree with all of that, but would add that maximum deviation is not
always the most desirable goal. The first time I tried taking hyperstereos
of the Grand Canyon, I tried to use 1/30 to 1/50 interocular, and got such
extreme depthn that the pictures were very hard to look at. On a second
trip I greatly reduced the interocular, and the results were much better.
William Carter mentioned recreating depth so that the dimensions along
the Z-axis are proportional to the other two - I think that may have
something to do with it.

When taking macro photos I've also had better luck with less than 1/30
interocular. (If I were trying for a very flat subject such as the face
of a coin, I would want much more than that to exaggerate the depth.)

>Practical example:  Suppose you are shooting fireworks.  The 1/30 rule will
>make the firework burst separate from the background (stars?) but
>might not give you adequate depth in-between the burst or different bursts
>within a small area.

I've had a very pleasing amount of depth in fireworks photos using a 4-foot
interocular. (And I *know* the nearest parts of the fireballs were much
more than 120 feet away.) Before I built the 4' bar, I used a 2' bar,
and the pictures had significant depth, though they seemed a little
"flat" to me. I may get the 6' bar built one of these days, then I can
report on that. :-)

John R


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