P3D 3D Screens & NSA Richmond 8/6-10

[WDuggan3D <WDuggan3D@xxxxxxx>]

Attention Lawrence Haines and Joe Feldman:

Yes, a sliver screen is a must to reflect polarized light
back to the viewers without depolarising the light, but
all silver screens are not equal.

Flat silver screens hotspot in the center, and are bright
about 15 degrees to the right and left of the center axis
of projection for a total of no more than 30 degrees of
coverage, and are therefore suitable only for narrow 
rooms, as anyone sitting more than 15 degrees from 
the center axis of projection will see a dimmer image.

Silver lenticular screens have vertical ribs, ridges, or 
lenses which spread the light out up to 45 degrees to 
the right and left of the center axis of projection, thus
providing up to 90 degrees of even brightness.  The 
flat or ovals (different brands have different configurations) 
along the top of the ribs and the flat areas in the valleys 
between the ribs reflect light back as with a flat screen, 
and the sloping sides of each rib reflects light back at 
a 45 degree angle, but all silver lenticular screens are not 
the same.

Three times the Potomac Society of Stereo Photographers
(PSSP), of which I am currently president for the fourth term, 
has tested all available 3d screen material, including the new 
flat Spectra material made by Da-Lite for video projection.  
In all three tests the Da-Lite WONDER-LITE and Da-Lite 
SUPER-WONDER-LITE and long discontinued RADIANT
LENTICULAR OPTIGLOW seemed the brightest over a 90 
degree range and depolarized the least.  KNOX silver lenticular
 and Spectra (flat)  slightly depolarized light, creating double images
 of white objects.  If you attended ISU 1993 Eastbourne, England, 
you may have noted that the large SPECTRA 2000 screen
slightly depolarized light and was dim to viewers more than 15
 degrees to the right and left of the center axix of projection.

Tripod silver lenticular screens often show up at yard or garage 
sales, flea markets, photo swap meets, auctions, estate sales,etc. 
at much lower prices than when new, and may be good buys if not 
damaged, but check carefully to make sure that the silver surface is 
not damaged.  Silver lenticular surfaces may be permanently damaged
by the acid oil on human skin, if touched, or by storage or transport
at temperatures higher or lower than normal room temperatures.
The silver can separate from the backing in bubbles so that the
surface looks like a bad case of measals,  Therefore do not store 
in an unheated garage or attic or leave in a parked car in the sun 
or in  cold weather, and store as near vertical as possible rather
than horizontal to minimize flatspotting.  When you erect a tripod
silver lenticular screen, you must tension it but pushing down and
 locking the mechanism so the horizontal ladder marks will disappear.

As to size, project your image on any surface, such as the wall, 
where you plan to use your project-or-view, and measure the size 
of the image, and purchase a larger size screen.  They come in 40"
x 40", 50" x 50",  60" x 60", 72" x 72", and during the mid-1980's
Da-Lite made a few 72" high x 96" wide, which I would like to 
purchase if any of you locate one that size.

KODAK recommends that the best viewing area starts at 2 x screen 
height for the front row of seats to 8 x screen height for the last row 
of seats,  within the bright angle of view, with the bottom of the screen
at least 4 1/2 feet from the floor so that those seated in the rear can 
see  the bottom of the images over the heads of viewers in front of them.

At NSA Richmond August 6-10, 1998, we will have a seamless 
Da-Lite Super-Wonder-Lite Silver Screen 7' high by 21' wide able to
show anamorphic (wide screen), two 7 or 8 perf (full-frame) side by
side, three  5 perf (Realist format) slides side by side, or four 4 perf
half-frame slides side by side 52' from the main projection platform.

Please advise me as soon as possible if you can produce a 10 to 
30-minute show, title, subject description, format, audio, etc., and 
I will snell mail the application forms to you.  We have the best 
facilities ever in the downtown Mariott with many museums, historic 
sites, statues, sculptures, cafes, shops, stores, waterfront, etc, 
within walking distance of the hotel.  Let me hear from you.

Season's Greetings!  William A. DUGGAN, APSA, NSA Projection
Consultant and PROGRAM COORDINATOR for NSA '98 Richmond. 




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