Firehawk - Black Level real or perceived? - AVS Forum
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post #1 of 7 Old 01-19-2002, 10:29 AM - Thread Starter
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I have a question for those knowledgeable in screen technology (Hopefully Don Stewart).

Is the enhanced black level on the Grayhawk and Blackhawk materials really in increase in measured contrast ratio over a Studiotec 1.3? Would a light meter actually give a numerically larger ratio?

I suspect that it won't and that what we percieve as improved black level is just that - perception. Now, I have no problem with being fooled into believing I am seeing more contrast. As long as the picture looks great, I'm happy. This is just a question for my own knowledge base.

I cannot see a way for the screen to differentiate between low level signals and high level signals without being a non-linear device. It would have to reflect a higher pecentage of high level brightness than that of low level brightness in order to change the actual measured contrast level.

The only other thought I have is that the screen could be pattern dependent. High intensity light would be sent back over a smaller viewing angle than low intensity light. This would also increase the measured contrast ratio on axis. I just don't lknow if either of these are realistic possibilities.

In any event, I am just looking for a scientific answer so my brian doesn't hurt when I try to figure it out by myself. I'm perfectly happy with being fooled, and in fact, I am planning to order a Firehawk for my soon to be purchased Marantz.

Greg
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post #2 of 7 Old 01-21-2002, 03:36 AM
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I think there are both real and percieved advantages. If there is any ambiant light present in the room at all, the screen will reject ambient light that is off axis from the viewer and give a truer black than a normal low gain screen. I think the advantage of the grey material is mostly perception, but I think there actually have been some measured improvement in contrast going to a grey screen. I'd like to see some data on this though too.


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post #3 of 7 Old 01-21-2002, 09:43 AM
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I just received some information on the new Da-Lite High Contrast Cinema Vision (gain 1.1) grey material and it is suppose to result in an increase in measured contrast of approximately 10% over the standard Cinema Vision white material.
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post #4 of 7 Old 01-22-2002, 01:13 PM - Thread Starter
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Would someone from Stewart like to comment? I'm sure you guys know the real scoop.

Greg
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post #5 of 7 Old 01-22-2002, 08:31 PM
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Ok here's the real scoop. :D Look back into the archives for the Greyhawk testing thread, if it's still available.

At that time Don Stewart posted test results from the original Greyhawk beta screens. As you may expect on-off contrast ratio was virtually the same. The black level gets lower, but the white is propotionall less. Where the contrast ratio increased was in ANSI contrast measurements where that was a significant increase (I remember 10+%). This will be visible as an increase in contrast in any scene that is not completely black. This is in addition to any gains in ANSI contrast you get from the grey screen absorbing backsplash from the room. The increases appear to primarly come from the optical gain coating which rejects off-axis light.

Anyways, in almost all cases if you have a digital projector and light to spare you will benefit to some degree from a greyscreen of any kind and more so from screens of a certain kind (i.e. the ones with an optical coating).

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Kam Fung
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post #6 of 7 Old 01-23-2002, 02:20 PM
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Kam,

Is the optical coating on the firehawk similar to those used on other retro-reflective screens - which 'virtually' eliminates off axis light and help light to return on its same path?

Just curious, because I'm currently using a DaLite Highpower (retroreflective) screen and I'm interested in seeing the results of a Gray/Fire Hawk. I would be willing to give up brightness if the image didn't have any uneven brightness issues. My highpower doesn't have hot spot issues, but it does get brighter when in the absolute center and it tends to fade as you look toward the corners.

I guess why I'm asking is because I'm looking to avoid the light scatter type screens. I might as well use paint in that case if I wanted the projector light to scatter and be absorbed thru-out the room. Obviously all screens do this for the most part, but the retro-reflective designs definitely seem to help give a more visible gain. Add that to the benefit of a gray material and I think I would be a happy camper.

Brian

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post #7 of 7 Old 01-24-2002, 09:32 PM
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Brian,

So far as I know the coating is not retro-reflective. You only get that on glass bead type screens.

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Kam Fung
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