Grey screen with gain? - AVS Forum
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post #1 of 8 Old 11-14-2001, 06:32 AM - Thread Starter
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Is it possible to have the advantages of a grey screen with a moderate gain? Seems this would work well with DLP's.
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post #2 of 8 Old 11-14-2001, 07:36 AM
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I am far from expert on this subject, so if I'm grossly incorrect, I imagine someone like Don Stewart will straighten me out ;)

I don't see having a +gain grey screen as being possible.

You're getting some absorption of light, so I don't know how you could get a + gain out of that.

Come to think of it, how does a screen get a + gain to begin with?

Don? Bueller? Anyone?

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post #3 of 8 Old 11-14-2001, 08:30 AM
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I personally think that a Gain >1 and gray screen is absoulte nonsense.

What do you want? Gain > 1 or gain < 1? :confused:

Gain=1 is a plain white wall, for gain > 1 you have to make some coating, for gain < 1 you paint it gray. But why BOTH? Cool, you get a gain of 1 AND hotspotting :D
so the only reason for building such a screen woul be: You like the hotspotting and reduced viewing angle effect but not the gain you will get. :)

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post #4 of 8 Old 11-14-2001, 11:30 AM
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The Greyhawk does just what you guys are saying. There are real benefits to it as well. There are two way to get an effective 1.0 gain screen. Either have a screen that is painted white with a flat surface coating or have a screen that is grey .8 and then put a glossy coating on it to bring it back to 1.0 (this is similar to what the greyhawk does)

The benefits all come down to room interaction. If you were projecting in outerspace or in black room that had no lights, there would be no difference between a "flat" 1.0 screen and a "glossy" 1.0 screen other than a very mild hot-spot that the glossy screen would have. That's the disadvantage.

The advantages are when a non-ideal room is used:

1. The glossy screen can help divert any light that is hitting the screen to the other side of the screen instead of saturating the screen.

2. The gloss also improves ANSI-type contrast ratios even if there are no lights on. This is a little difficult to explain but if the room is small relative to the screen and or has a light color to it, the overall grey nature of the screen will help reduce the impact of reaborbed light from the image that is being projected. To say it differently, the bright areas of the image illuminated the room. The room then emitts some of this light back to the screen which will effect the dark regions of the image. The gray screen helps this process.

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post #5 of 8 Old 11-14-2001, 01:49 PM
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Mr. Wiggles,

Ok, I'm still not getting the gain issue. The projector emits a certain number of photons X.

To go positive on gain,wouldn't you need to emit a certain larger number of photons (X + N)? If this is the case, where are they coming from?

I must not be connecting things correctly together in my brain.


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post #6 of 8 Old 11-14-2001, 06:53 PM
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Hi John,

You can find a pretty good explanation of screen gain and its characteristics here:

http://www.da-lite.com/educational_m...ils&issueid=48

I hope this helps :)
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post #7 of 8 Old 11-14-2001, 09:26 PM
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Bob,

Thanks -- it was my literal brain in action, associating + gain in an absolute sense, instead of how its really derived.

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post #8 of 8 Old 11-16-2001, 08:48 AM
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:) John, (Brightstar!)
now that was fun at CEDIA.As Jason Turk said-"star of the show!"
It makes lampliters ...........tremble!
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