P3D RE: P3D focusing stereo cameras

["Greg Tank" <tanker@xxxxxxxxxxxx>]

Jacques Cornet wrote
>I inherited a Kodak stereo, used in the sixties to get the necessary images
>for "stereo chromos", small stereo pictures >packaged with chocolate bars.
>So a "professional" use.

>The photo-laboratory saw that there was a difference in focusing between
>left and right pictures. Contacted Kodak Brussels Belgium. Received the
>answer that it was voluntary and destined to better the impression of
depth,
>the brain mixing right and left pictures...An excuse, or a fact?

Weather Kodak did or did not actually set the camera up this way I would not
know. More on this later. One camera that I am aware of that did have each
lense focused at different distances was the Stereo Graphic. This type of
focus set up is called fusion focus and the reason was that it was a fixed
focus lens so the compramise was to have one lens focused to produce focus
close and one lens to produce focus at a futher distance. Then when viewing
a person fuses the two images to achieve a higher depth of field than the
camera actually has. Does it work? Welllll. sorta works sorta not. If you
want to read more on the Stereo Graphic and its fusion focus approach  - Gil
Van Horn wrote a nice piece in INSIDE 3D Vol. 3 No.2 Summer of 99. page 33

As for the Kodak, since the lenses have focusing capability I believe that
the ideal situation is to have both lenses focus at the same distance. This
is what I do when I perform a C.L.A. on a Kodaks, You could check your
camera using a ground glass on the film plan and us a 10X or 20X
magnification loupe to assess the cameras condition. Adjusting the focus on
a kodak is straight forward if you have a piece of ground glass or
equivalent, a small phillips head screw driver and a bent paper clip. If you
want to attempt it drop me an email off line.

gotta go,
tanker

Gregory A.Tank     "tanker@xxxxxxxxxxxx"