Keystoning in Beam Splitter Images

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

>> When looking at beamsplitter-taken images (with
>> keystoning) in a Dr. T'd red-button viewer, there is "no
>> drastic discomfort".  No discomfort at all, actually. 
>> So "some keystoning" certainly is no problem at all.  At
>> least on the ones I tried.
>> 
>I've had the same experience. I know what Keystoning does in 2D, but 
>I'm unclear what it causes in 3D, because the pictures I've seen that 
>everyone says have it, display no distortions to me at all!
>
>So what _is_ the effect in 3D?

To see the effect you have to look towards the edges.  This manifests
itself as a vertical offset.  There is no offset along the vertical
line that passes through the center.  But there is an offset that
increases as you move away from the center.

I have seen at a beam splitter image mounted in a Realist format
frame (I think it was Greg Erker's wedding) and could see the
offset at the edges.  It appears as if there is a vertical 
misalignment that if you try to fix in right side, you make
it worse in the left side.

(I am sure someone can provide a nice ASCII diagram to demonstrate this)

The reason that perhaps you have not seen it is that you are looking
mainly at the center, where the area of interest usually is.

-- George Themelis


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