Newsgroups: rec.video
Subject: Re: Sony Projctr Questions
From: michael@sunbeam.ksc.nasa.gov (Michael D. Myjak x7-3286)
Date: 11 Nov 92 10:19:22
 m><MICHAEL.92Nov5104813@sunbeam.ksc.nasa.gov> <20850@fritz.filenet.com>
Organization: NASA, Kennedy Space Center, FL.
In-reply-to: daver@felix.filenet.com's message of 11 Nov 92 02:34:17 GMTLines: 57


   (Michael D. Myjak x7-3286) writes:
   >  As for the screen... don't get a glass bead screen.
   >There are much better products out now and Glass is not the most
   >efficient one.  One manufacturer has a screen material that has a
   >cooef. of reflectivity in the neighborhood of 4. Glass beaded screens
   >are in the neighborhood of 1. That translates to a picture that
   >appears to be 4 times brighter. 

   There is a direct tradeoff between the gain of the screen and viewing
   angle.  Currently, screens being installed in higher-end home theatre
   applications have a gain of about 1.5.  There is some pressure to reduce
   that even more.  Joe Kane prefers a screen gain of 1.3.  The room has 
   to be a little darker, but it's worth it unless you only ever want to
   view the picture from one chair.  From what I've heard, the best screens
   are from Stewart Filmscreen Corp (800) 762-4999.

   Dave

Who makes the "best" screens is a matter of opinion. Yes, there is a
direct correlation between reflectivity and apparent brightness... and
this are inversely proportional to the usable viewing angle. Perhaps I
wasn't too clear in my first post. So to put this in perspective, a
matte white screen with a gain of 1 will permit a 45-degree viewing
angle left & right of the centerline. Yes, a picture can be seen in a
region wider then that, but the quality and "viewability" is poor at
best.

 Screens with the highest gain (4, like the Silver Satin I mentioned
above) provide a viewing angle that is about half of that [of a matte
white] or about 22.5 degrees to either side of centerline.  Yes, this
45-degree viewing angle *is* a reduced angle for viewing but it
quadruples the brightness!

Most of my clients [which] have [a projection system] complained about
the picture's [lack of] apparent brightness more then any other
"defect" with this technology... including convergence, motion
artifacts and fringe-viewing problems.  This is probably due to the
fact that most people are familiar with direct-view CRTs and attempt
to equate their apparent brightness level to that of a projection
system. In all honesty, there really is no comparison... unless your
talking about the GE light valve... but then thats priced at $100,000
and above.

IMHO, when designing a room [be it media, theater, or board room] the
layout [obviously] determines the seating arrangement (with respect to
the projector.) This in turn determines the minimum and maximum
necessary viewing angle and given this maximum viewing angle, the
screen selection should be based on providing highest gain possible.
--
- Michael D. Myjak			
  Senior Technical Specialist, Systems Analyst
  McDonnell Douglas Space Systems Company
  Kennedy Space Center, Fl., 32815
  MYJAK@TITAN.KSC.NASA.GOV

Gravity. It's not just a good idea. Its the LAW!
Newsgroups: rec.video