P3D Window

[fj834@xxxxxxxxxxxxxxxxxxxxx (Dr. George A. Themelis)]

Great posting from Brenda Nowlan, the new PSSP projectionist :-)

>Bob Leonard said there is no difference between the
>various slide mounts, the windows are all in the same place for
>Realist.  Windows are all in the same place for Nimslo, just smaller
>windows.  But the spacing is the same.  

Approximately correct.  There are small variations between mounts as an
observant projectionist who has used Albion mounts and RBTs mixed in one
show, knows...

>I was a little confused by this
>because I thought I have heard reference to windows being different in
>relation to the stereo window, like close up, at the window, and
>distance.  What am I not understanding? 

The confusion comes from using the term "window" to mean both the openings
of a stereo mount and the impression of seeing a scene develop behind an
*imaginary* window in space.

The physical opening of the mounts should not be called "window", just
aperture size, opening, etc.  But it is the openings in the mount that
create the stereo window when the image is viewed in 3d either in a viewer
or in projection.  

The relationship of the scene with respect to the window is determined by
the position of the film chips with respect to the mount openings and not
by the size or opening of the mounts.

As Bob said, different mounts (should) have the same centers and it is only
the size of the openings that is different.  Smaller openings can be used
for cropping but also for correct placing of the stereo window.  The EMDE
mounts used to hold the mounts in a specific place and if you used a
close-up mount then the actual window, as seen in the scene, was placed at
4 ft. (or whatever).   But most mounts today do not  hold the chips in a
rigid way but allow you to slide them horizontally.  By sliding the chips
relative to each other you can determine where you want to place your
scene.  If the scene is a close-up taken with a Realist-format camera, then
you are forced to use a so-called "close-up" mount because you will run out
of mount opening space while adjusting the chips.  But you can use
different mounts just for cropping.  RBT is doing well by listing their
mounts according to the size of the openings and not using labels like
"Realist", "European", "Close-Up", etc.  These labels can supplement the
dimensions but the mounts have more use than what is indicated by the
labels.

>Mr. Duggin said that that is how properly
>mounted stereo slides show.  No adjustments and everything keeps
>moving.  I think he made his point to those that would listen.  He seems
>to really know alot about projection.

He is well-known to NSA and NSA.  He was the one involved in constructing
the large screens used in these projections.  He keeps the screens at his
house and brings them in for the shows. (His name though is Duggan :-))

Thanks for the exciting report!

George Themelis


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