P3D Best Polarizing Material?

[Bill Davis <bd3d@xxxxxxxxxxxxx>]

Greetings.

Time for me to pick the collective brains of Photo-3D again.

As some of you know, an ongoing project of mine for the past year or so has
been trying to find the best screen material for rear-projection stereo.
The main criterium is non-depolarization of the light, with secondary
criteria being minimal hot-spotting and minimal grain.

My method for testing non-depolarization has been projecting only one side
of a stereo pair onto the test screen and  viewing it through the opposite
lens of my glasses, basically seeing how much cross-imaging is visible. I
use a variety of slides, one of the toughest being an image of a floodlit
Chicago building against a night sky. With test materials set up in an
array, I can look from one to the other and select the best. My test
standard has been a Da-Lite V.I.P. silver lenticular screen.  When I find a
likely prospect, I switch on the other lamp and check the stereo image for
ghosting.

I found a material recently that looks promising, with apparently equal
performance to the silver screen, but now I want to know which is *better*.
 To really compare the two I need to eliminate as many losses as possible.
I should be using the best possible polarizers in the projector *and* in my
glasses.  For purposes of my testing, maximum polarization and minimal
scattered light would my main concerns.  The amount of light lost wouldn't
strictly be a concern for this testing, 'though I would probably leave the
good stuff in afterwards.     

I've got new Reel-3D material in my projector now, and have a variety of
glasses.  The projector material is better than that in the glasses, I can
tell.  Holding a peice in front of my eye and rotating it for maximum
extinction shows less ghosting than any of my glasses.

So..... what's the *absolute best* material to use for projection
polarizers? There has been talk over the years about the different options,
including Reel-3D, Edmunds and various camera polarizing filters, but has
anyone ever done a head to head test with names and numbers?  Bill Duggan,
maybe?

Someone (DrT?) had once talked about getting both grades of polarizing
material (Commercial grade w/25% transmission and Tech Spec w/38%
transmission) from Edmund Scientific and testing.  I don't recall reading
how that came out.


Best regards,
Bill Davis
mailto:bd3d@xxxxxxxxxxxxx



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