P3D Keystone distortion when projecting

[Ralph Johnston/Linda Sherman <copley@xxxxxxxxxxxxxxx>]

With short focal length projector lenses, one would tend to move the projector
closer to the screen and get keystone distortion.  (The left image is keystoned
differently than the right one).  This would be worse when using twin
Ektagraphics because the distance between the lenses would be greater.




>
> ------------------------------
>
> Date: Tue, 09 Mar 1999 22:41:50 -0700
> From: Rod Sage <rsage@xxxxxxxxxxxxxxxxxxxx>
> To: P3D <photo-3d@xxxxxxxxxxxxxxxxx>
> Subject: P3D Projection Lenses
> Message-ID: <36E605B2.5D8D@xxxxxxxxxxxxxxxxxxxx>
> MIME-Version: 1.0
> Content-Type: text/plain; charset=us-ascii
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>
> >I am, lonely projector guy way in the back...Ý Okay, so why not just quit
> >whining and get, say, 4-inch lenses?Ý Or, better yet, 3-inch lenses!Ý Well,
> >there were/are stock standard TDC manufactured 4-inch lenses given your
> >willingness to part with more hard earned cash.Ý There are not 3-inch lenses
> >and per my fooling around with the TDC it looks as though it will only
> >accept 3-inch lenses if you do some serious mods to the lens housing shell
> >whatever-you-call-it casting, like cut the back half of the damn thing off.
>
> Someone in our stereo club demonstrated his TDC projector into which he
> mounted a pair of 75mm (<3") Nikkor enlarging lenses. The image quality
> was amazing. Big, bright and clear! He had to machine the barrels to
> fit, which was quite a job. Cost of used Nikkor 75mm is not too cheap. I
> have 4" lenses on one of my TDC 116s and they work quite well. They can
> fill a 50" screen from about 12'.
> RDS


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