[photo-3d] Re: questions about formulas

["Abram Klooswyk" <abram.klooswyk@xxxxxx>]

David siggyblue wrote Jan 10, 2001:
> (...)I have a 35mm realist with which I like to make
> holmes type views.  My camera is 35mm f.l. and my
> holmes stereo viewers are of focal length many times
> longer, is there an adjustment I can make to
> compensate for this difference?

George A. Themelis  Jan 11, 2001:
> You have not taken into account the magnification
>              (enlargement) during printing... (...)
> Do you know what the FL of your viewer is?

Classical Holmes stereoscopes have mostly about 20 cm
(7  7/8") focal length, that equals 5 diopters. See
Allan Lewis post at:
http://www.pauck.de/archive/mailinglist/photo-3d/
mhonarc/msg04405.html
(URL should on one line for your browser)

So for an "orthostereoscopic" result your print 
magnification should be 200 mm / 35 mm or about
5 to 6 times. But then your vertical print size 
would be 12 to 14 cm (5 inch), which your stereoscope
wouldn't accept, and the separation of the views again
would get too large. You would have to trim off much.

When you insist on the Holmes stereoscope, I would
just accept its too long focal length, and enlarge to
standard stereoview size, or little over, and trim a 
little. Many stereoscopes have longer FL then the 
stereocamera, including 5P viewers and View-Master 
viewers. Tolerances in stereoscope viewing are large.

Abram Klooswyk