Argh!!

[P3D John Bercovitz <bercov@xxxxxxxxxx>]

I said:

> The axes of the lenses themselves are parallel or you would 
> indeed get keystoning.

Now why'd I have to go and say _that_?  If you swing a lens axis, 
you swing the plane of best focus relative to the plane of the
film: the two planes are no longer parallel.  If you want to
get keystoning, you have to swing the film plane relative to
the direction the camera is looking in.  (And then you would
consequently very likely have to swing the lens to get a sharp 
image across the film plane.)  

So: To avoid keystone error in a 3D pair, keep the image planes 
parallel.  To make the planes of focus coincident, make sure the 
lens axes are parallel.

Sorry for sending out misinformation.
John B


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End of PHOTO-3D Digest 1377
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