P3D 3D Video with rear projection

["Rafael Ramirez" <globalimages@xxxxxxxxxx>]

>From: Andrew Woods <andrew@xxxxxxxxxxxxxxxxxxxxx>
>Actually, I don't think the video was projected at 120Hz.
>Here's what the equipment was and what it did:
>The Titanic footage came as a pair of Betacam SP tapes (one left tape
>and one right tape).  The left and right video feed from the two
>Betacam SP machines went to a pair of QD7500 line doublers.
>The left and right line doubled signals were then sent to a pair of
>3 gun CRT projectors (with circular polarisers fitted to the output lenses)
>for projection onto the 3D Black Screen.

Do you know what type (brand) of polarized filters where used and how well
did they worked?  I did several tests with polaroid's cardboard glasses
(don't recall them being called Polaroid 2's, by the way) and polaroids
linear's+retarders and came to the conclusion that the extintion
ratio was slightly worse (compared to a "dificult in practice" perfectly
crossed linear polarizers).  Used a slide projector as light source and a
Minolta digital light meter, and different types of filters (HN35, 38, 38s,
42).  Never tested polaroids "all in one" circular polarizers, although
obtained a quote for their right/left products.  Anybody knows how well they
work for stereo?

I considered circular polarization for a permanent attraction in a zoo park
running off dual CRV laserdisks (a special component-format videodiscs made
by Sony), dual CRT projectors & front metalized screen, but the (higher)
cost of the glasses and my inability to obtain any better extition with them
led me to use linear instead.

Incidentally, anybody knows sources for circular glasses (polaroid still
sells them?, Stereographics?, Vrex?, 3DTV? any comments as to which are
best?)

I'm also interested in details about the QD screen itself.  Can you
elaborate
(was it foldable, "plastic"-like?, rigid? Lenticular? etc?  Do you know how
large in size can it be made?)  I tested Polacoat rear screen material and
found it usable (it depolarises only slightly, it's foldable & washable).
Also tested some "shower curtain" materials, with similar results. Any
experiences as to which rear material depolarizes the least?

Actually I run a mini film festival in the Canary Islands several years ago
using a Vrex projector and a Polacoat screen.  I also run another festival
(this time in 35mm film), but had to use video for the first one due to the
inability to obtain movies dubbed in Spanish in film format.

By the way, be warned that the Vrex projectors, at least mine, had its
micropol filter fade (=lose polarizing efficiency) *tremendously* after just
little use, and to the point of becoming unusable for stereo in just 8
months (too much crosstalk).  Obiously the polarizing properties of filters
made through this "iodine printing" process are not that stable.  Polarizing
efficiency was never too great, although certainly good enough, if it would
only last at least a couple of years...  This makes me wonder if anybody
knows the expected lifespan of transparencies made by the Rowland institute
printer inks.




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

wil be greatly appreciated.
>
>Regards, Robert
>rodeck@xxxxxxxxxx
> Thanks. 

Hi Robert (and others) - the relatively recent (within the past year and a half
or so) archives are keyword searchable and can also be browsed if
you have www access. If not, you can ftp into the archives and
look at them that way (but without the search feature, of course).

In both cases, point your query towards

bobcat.etsu.edu

For ftp, use the userid of "anonymous"
(use your e-mail address as password) 

or for the web

http://bobcat.etsu.edu

if using a web browser and follow the links.

The current version of the search engine (glimpse) is remarkably
fast, and also allows regular expression searches and "fuzzy" matching,
which allows for mis-spellings (ie, in case you are searching for
"Sputnik" and spell it "Sputnek"). With web access, it shows you the
matched word in context, and also allows position dependent searching
(ie, you can look for "medium format" but exclude "format medium" if you
wish).

For example, searching for the keywords anagl and glass with case insensitivity,
and substring matching yielded the following (this is a partial listing)...

==========

File /bobcat.etsu.edu/ftpdir/photo/photo-3d/digests/PHOTO-3D_digest_0878.txt

       line 367: red and blue filters (from a pair of Anaglyph glasses) over 

File /bobcat.etsu.edu/ftpdir/photo/photo-3d/digests/PHOTO-3D_digest_0895.txt

       line 711: 1.Does anyone know the best place to buy anaglyph paper glasses? 

File /bobcat.etsu.edu/ftpdir/photo/photo-3d/digests/PHOTO-3D_digest_0896.txt

       line 612: >1.Does anyone know the best place to buy anaglyph paper glasses? 
       line 841: To continue the anaglyph glasses question, can someone provide 
       line 853: > To continue the anaglyph glasses question, can someone provide 

File /bobcat.etsu.edu/ftpdir/photo/photo-3d/digests/PHOTO-3D_digest_0899.txt

       line 502: anaglyph, pulfrich, polarized and fireworks glasses. Apparently an offer too 

File /bobcat.etsu.edu/ftpdir/photo/photo-3d/digests/PHOTO-3D_digest_0939.txt

       line 497: (Where did you put those anaglyph glasses, anyway

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Digest #896 looks promising, so you can click on that and find Marvin's posting from 
last June...

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