Re: Keystoning in Beam Splitter Images

[P3D Gregory J. Wageman <gjw@xxxxxxxxxx>]

George explained:

>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 feel compelled to point out that a stereo mirror attachment doesn't
HAVE to produce keystoning.  If the inside and outside mirrors are
kept parallel, the length of the optical path is the same across the
images, and there is no keystoning.  It's only when the outside
mirrors are pivoted away from parallel that the optical path becomes
uneven and distortion results.

So maybe the reason some people aren't seeing keystoning in all of
their beamsplitter images is because there isn't any, or isn't
enough to be obvious.

By the way, if the mirrors in the matching viewer are parallel,
then the viewer will NOT cancel out any keystoning in the slide.

	-Greg W.


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