Interlens Separation and the Window

[P3D <LeRoyDDD@xxxxxxx>]

     Paul Boyer said, in the posting with his table for closeup and macro
variables:

"The values are very realistic: they assume that the target is right at the
window.  If one wishes to drop the target back from the window, one shoul[d]
reduce I slightly."

     My understanding is that interlens separation, "I," only affects the
amount of image point disparity recorded on the film, the amount of "depth"
if you will. This will affect the comfort in viewing or whether a scene will
"fit" within the range of a given mount/viewing system, but not the window,
which is determined by where the masking/mount apertures are placed in
relation to the taken image.

     The window is defined when the viewing/mount apertures each contain the
same amount of the image. The scene in front of or behind the window will
have less of image at the edges in each case.
     Another way of saying this is that the disparities between image points
and the edges of the viewing/mount aperture are zero at the window.

     Illustrative of the independence of taking variables on the window is
the fact that the "window" can have dimension and shape of its own. It can
slope into or out of the scene from any direction or bow in or out. This can
save "window violations" or be used for esthetic considerations(easily
overdone!).

     In camera "windows" formed by the film apertures are determined by
whether the lens axes are parallel, diverged or converged... respectively; at
infinity, beyond infinity, nearer than infinity. I seem to recall the Realist
lens shift gives a seven foot window and the Kodak gives an in-camera window
of five feet. Piper lists the in-camera windows for various cameras in his
Technical Pages, I think, which I don't have at hand. :=(

     I have no opinion on the correct use of the Five Dollar Trifecta Window,
however. :=)

LeRoy Barco
LeRoyDDD@xxxxxxx


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