Grayhawk or ND filter? - AVS Forum
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post #1 of 4 Old 06-04-2001, 01:09 PM - Thread Starter
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I have a general question with regard to the new low gain screens such as the Grayhawk. Suppose that I own a high light output (> 1000 L) DLP or LCD projector and a screen with a gain of 1.3. This may be an ideal situation for a low gain screen. My question is wouldn't I get the same result by putting an ND filter in front of the projector and keeping the 1.3 gain screen?

If the answer is no, then the screen must have some kind of nonlinear relationship between the incoming intensity and reflected intensity. Comments.

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John Moschella

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post #2 of 4 Old 06-04-2001, 05:48 PM
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If your room is perfectly dark and your walls are perfectly nonreflective, the answer is yes. Otherwise the answer is no. A Greyhawk will attenuate the ambient light along with the projector, the ND filter will only attenuate the light from the projector.


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post #3 of 4 Old 06-04-2001, 07:42 PM
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If it were truely that easy, I don't think there would be any enthusiasm for the Greyhawk. The ND filter won't do anything to improve the contrast ratio of the image, but the Greyhawk seems to dramatically increase it by making the blacks darker and keeping the whites bright.
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post #4 of 4 Old 06-06-2001, 07:22 AM - Thread Starter
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Quote:
Originally posted by rbmartin:
If your room is perfectly dark and your walls are perfectly nonreflective, the answer is yes.
Richard
I want to consider the case with a perfectly dark room to remove the abient light issue pointed out by Richard. Reflections off walls will certainly be a second order effect, but for the sake of argument lets also say the walls are nonreflective. Then, it all boils down to the issue of the screen reflectance having a linear relationship to the incident light intensity.

Jonmx,
Is the contrast ratio actually improved in a totally dark room? Are there measurements of this? This could just be a perception that the contrast ratio is greater and you could get the same perception with an ND filter and a higher gain screen.

John

[This message has been edited by John Moschella (edited 06-06-2001).]

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