P3D Re: Realist system flawed?

["Greg Wageman" <gjw@xxxxxxxxxx>]

From: Dr. George A. Themelis <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>


Boris Starosta wrote:
>>Remember, the full 35mm frames produced by my twin rig are some 50%
larger
>>than those coming out of a "standard" (5p? ANSI?) Realist.  Add the
>>relative "enlarging" effect of the proper focal length in the
inexpensive
>>"Pinsharp", and with 2x2 slide pairs you have a stereo view that is
>>practically double the size of a Realist slide viewed through the
>>inexpensive Radix viewer.
>
>I am sorry, I cannot follow these calcuations... For one thing, my 44
mm
>Realist red button viewer produces larger images than your 50 mm
Pinsharp.


Me neither.

The Realist chip is the same height as a full-frame 35mm chip.  However,
it is 5/8ths the width.  Or, put the other way, the full-frame chip is
36mm/22.5mm=1.6 times wider than the Realist chip.

Magnification of a simple lens is approximated as 250mm/f, where f is
the focal length in mm.  The 50mm Pinsharp lenses give a magnification
of 5x, whereas the slightly shorter Realist lenses give 5.682x.  (Think
of it this way.  The shorter the focal length, the closer the object is
to your eye, and the bigger it appears.)

So, your Pinsharp's magnification of 88% of the Realist's, of an image
that is 160% the width of a Realist's gives you an image which is 141%
the width of a Realist image in a Realist viewer, but only 88% as tall.
This is a long way from "practically double the size". :-)

If you've never done so, Boris, I strongly recommend remounting a few of
your images in full-frame RBT mounts, and view them in a Red Button
which has been modified for 8-perf.  You might be in for a rather
pleasant shock, if you have only the Pinsharp to compare against.

     -Greg W. (gjw@xxxxxxxxxx)



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