Re: Converging lenses (was: Window reversal); D|s-TortiO|\|s

[P3D Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

Mike K. writes

>Hmmmmmm... okay you want a technical for-reality's-sake sort of reason for
>keystoning.

Mike, I think your missing the point. You should read my post in context
with all my other posts regarding this subject. It's not a matter of what
I want, but rather the impetus of the discussion. That is, is keystoning
is a valid effect?

But it looks like I'll have to summarize. First, the technical part
has nothing to do with reality. The reasons for avoiding keystoning
are valid for reality or anything created from your imagination.

>I can think of one.  If my goal is to take stereo photographs which are
>intended to be viewed using the type of viewer commonly used for 
>"beamsplitter" stereo attachments, then keystoning would *improve* the
>technical reality-simulating result.

This doesn't apply to the current discussion. We are talking
about breaking rules for achieving new effects, using a twin camera
setup. The implied viewer in this discussion IS NOT a beamsplitter
viewer, but rather a normal viewer that 99% of the public uses.
The impetus of this discussion is, if keystone distortion can be
used in the above case. So, still no valid reason has been given.

Second, in the case of beamsplitter setups, one is not *improving*,
but rather correcting for an inherit distortion fault by the viewer's
anti-keystoning.

>As I understand it, beamsplitter attachments produce keystoning, but
>it's "okay" because the matching viewer undoes it -- yielding an 
>undistorted image.
>
>So, when NOT using the beamsplitter (or even when doing so) keystoning
>is desireable in order to compensate for the viewer's anti-keystoning.

Yes in this case it is true and valid but (again) has nothing to do
with the discussion. I do understand your reason for stating but I
was not asking for ANY reason for using it but rather, why would
anyone want to introduce keystone distortion and look at it!

Third, why would you want to *improve* the image??? Don't you want
to keep the keystone distortion introduced by the beamsplitter or by
converging your camera!?! I thought, that the keystoning was a desired
effect!

Anyways, I was having exactly the same thoughts as Greg W. on this
whole matter, that, we can go on forever discussing this. So unless
someone can come up with valid reasons for wanting to achieve this
effect and KEEP it, I think we have exhausted the possiblities and
turn the floor to any other bright, open minded people. :-)

Gabriel, lo oking for new horizons.
           >
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