P3D Re: Window for Projected 2x2 Slides

["Oleg Vorobyoff" <olegv@xxxxxxxxxxxxx>]

My question:

>> What is the recommended way to set the window for projecting 2x2
>> slides using dual projectors?
>> I take my slides with a single 35mm
>> camera mounted on a slide bar.  The slide bar by default puts the
>> window at infinity.  With the RBT 41x101 full frame mounts it is a
>> simple matter to diverge the chips to recede infinity behind the
>> window. Are there 2x2 mounts available with a 33mm aperture like
the
>> RBT mounts(instead of 35mm) that will allow the chips to be, in
>> effect, diverged?


Paul Talbot's answer began:
>
>You can come close.  Try Gepe slide mounts, available in a
>wide range of sizes.  Here are some options...
>
and ended:

>
>Boris Starosta of this list is known for advocating slight
>toe-in.  But he gets a fair amount of argument on that point.
>
>I hope this helps.
>


Thanks very much for your reply.  It was most helpful.  I think I will
continue to use the slide bar straight for most shots and remount the
slides if they are to be projected.  If there is time during the shot,
I will use toe-in.  Here's my procedure:

1. Determine nearest and farthest objects in picture.

2. Estimate the amount of slide bar shift (or tripod shift for a hyper
situation) that will give 2mm shift on film between nearest and
farthest objects.  For normal pictures the shift would be about 75mm.
With a little experience, one can estimate the right amount of shift
by gut feel.  If in doubt, I take several shots at different shifts.

3. Take first shot.

4. Note horizontal position of near object in frame of first shot.

5. Shift the amount estimated in step 2.

6. Toe in as necessary to put the nearest object in the same position
in the frame as it was on the first shot.  There are enough dust
specks in my viewfinder that I can usually find a suitable
constellation of them for positioning reference.

7. Make sure nothing has moved since first shot.  If some thing has,
waste no more film.  Otherwise...

8. Take second shot.

My feeling is that it is usually best to use as much of the z-axis as
available behind the window, that is, hypo or hyper as necessary to
give a full 2mm shift on film.  The projection viewing experience
seems so artificial to me that I don't expect that a true ortho
version of a slide would be any more compelling than an exaggerated
version.  I think it will usually be the other way around.  Since I am
relatively new at 3D, that opinion is subject to change.

Oleg Vorobyoff


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