P3D Zoom lenses on Ektagraphics (hijacked from Sell 3D)

[Greg Dinkins <dinkins@xxxxxxxx>]

A discussion of lenses for Ektagraphic projectors on S3D:

From: Tom Deering 
>>I can get a used pair from B&H in New York for $255 each, which
>includes a zoom lens and a tray.  Is this a good price?

From: -Greg W. (gjw@xxxxxxxxxx)
>Yes, it is a decent price.  In Usenet groups, used Ektagraphics are
>often offered for $300 or more.  However, I'd stay away from the zoom
>lens; for stereo applications, it will cause you no end of grief in
>trying to match image sizes, and if the barrel rotates like I think it
>does it will also throw your polarizers out of alignment.

FWIW:
I have little experience with 2x2 projection, (like 6 times), but I'm
chipping into the discussion because all those experiences were in different
places and the zoom offered a nice accommodation for different screen sizes,
different throw, etc. in 4 of those cases. I had no problem setting the two
4-6 inch zoom lenses to match on 4 and 5 foot screens, viewed from about 10
feet away. Two times we were using a Wess alignment slide and that made
setup easier.  As far as the two polarizers' orientation, the zoom
magnification was set once as we set up for projection of the widest image,
then the polarizers were simply taped to the front of the lenses. Focusing
during projection did not affect orientation of the polarizers.  

The other two times I've been involved in setting up 2x2 projection were for
New York Stereocopic Society meetings. The museum AV technician offered
matched 7inch "auditorium" lenses which filled the 6 foot screen from the
back of the room. We gladly accepted. No fuss with zooms.

Greg, I wonder if you've personally had problems matching zoom sizes? Or are
you relying on good advice from AV professionals whose philosophy is to
eliminate variables in projection?

Tom, we could get together if you want to try out my setup, which is a
little sloppy due to being an agglomeration of hand-me-down projectors and
one of the (zoom) lenses being borrowed. But then you could get an idea of
which variables are important to you.

My summary: If you're installing a home or auditorium theater then fixed
focus lenses would be fine, and zooms will just add a chore. But if you take
your show on the road, the zooms can be nice. 

Greg Dinkins
dinkins@xxxxxxxx


------------------------------