Grayhawk vs. Dalite HC "Color Temperature" - AVS Forum
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post #1 of 14 Old 06-24-2001, 08:48 PM - Thread Starter
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Hi All,

Just trying to decide on a Stewart Grayhawk or Dalite High Contrast gray screen and an interesting difference has come up. I have screen samples from both companies and have been comparing them side by side.

From what I've read in this forum everyone seems to agree that the Stewart Grayhawk is a lighter shade of gray than the Dalite and I can confirm this. However, it also seems like the two have different color temperatures. The Dalite HC material seems to me to have a lower color temperature, whereas the Stewart seems to he higher. To put it in relative terms, if the Dalite is close to 6500K, the Grayhawk seems to be closer to 10,000K. The fact that the Stewart looks slightly blue in direct comparison to the Dalite, seems to confirm this.

Am I nuts? Can screen material exhibit a color temperature similar to display devices?

If I am correct and screens can affect the color temperature, it seems like the display device would need to compensate for the screen if one is trying to reach a specific color temp like 6500K.

Chris
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post #2 of 14 Old 06-25-2001, 12:32 PM
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You're not nuts, if your "white" screen has a red-tint it will definitely affect your image! Check out the Stewart website, I believe they test the spectral response of their screens vs. an established standard. The results should be available on their site in the screen material section. I don't know if Da-Lite publishes their test results (or if they test at that level...), so it would appear that the Greyhawk would probably give you the most accurate colour balance. Of course, if your projector runs "cool," as most projectors do out of the box, the Da-Lite's lower colour temperature might provide a nice complement. Obviously the ideal solution is to have your projector calibrated to 6500k on your screen.

Regards,

Kam Fung
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post #3 of 14 Old 06-25-2001, 11:50 PM
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Kam,
More variables due to screens.Most I have tried mute colors and add grey to whites.And those are so called white screens.Kodaks screencheck program and paper is pointing the way(brightness as shot not too low,not too high)
Ok I admit it-I need help here!
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post #4 of 14 Old 06-26-2001, 09:29 AM
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Cris,
Hope you will post all the details of your comparison!
Thanks.

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Here's to deeper black and higher contrast on a 120" HP screen.
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post #5 of 14 Old 06-26-2001, 02:54 PM
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I took measurements on a Stewart Ultramatte 150 and a Greyhawk under natural (mostly sunlight) light. The Greyhawk was .01 lower in x and y, yielding 500 deg higher color temperature. Statistically significant, but not all that noticeable. Certainly not enough to explain Chris' observation.



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post #6 of 14 Old 06-26-2001, 10:19 PM
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<FONT face="Arial">Text</FONT f>
I saw this topic and thought I might try to add some hard numbers to performance of Da-Lite's HC Da-Mat fabric. Here is what an independent source found as a result of testing for color shift and luminance values. The method for testing was to try a recreate a real live scenario. This is what was determined.

"First, we took readings from the projection system using a 1.0 gain white screen as our base.

With a 100 IRE Window being projected, we had 9.46 foot lamberts and an X value of 334 and a Y value of 351 (color coordinates).

With a 40 IRE window projected, the values were: 1.39 foot lamberts, an X value of 317 and a Y value of 323.

We then took the 0.8 gain HC Da-Mat and put it into the exact same configuration (nothing was changed).

With a 100 IRE window projected we had 6.13 foot lamberts, an X value of 338 and a Y value of 353.

With the 40 IRE window, we had 0.88 foot lamberts, a X value of 322 and a Y value of 323."

So as you can see from this small test, the HC Da-Mat has very little color shift. What we intended for this fabric to do is to lower black levels and shift the grey scale of the image. We did not want to affect the colors.

Thanks,

Blake


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post #7 of 14 Old 06-27-2001, 12:18 AM - Thread Starter
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Hi All,

I will try to post some images of the screen materials I have. My first impression is that the difference seems to be more than 500K, but I realize that the eye is often decieved.

In fact, it seems more fair to compare the backside (the uncoated side) of the Stewart Grayhawk to the Dalite HC since the Stewart's optical coating is what causes the *very* slight shift to blue (a "cooler" color temp). When I compare the back of Grayhawk sample to the Dalite HC sample, indeed the difference is only in the level of gray and there does not appear to be a differnece in color "temperature".

Again, I have found that both products work well with my Sanyo PLV-60. Aside from the differences in color temp that I seem to be seeing, each has its strong points. The Dalite seems to provide more improvement in black level. Since the Stewart has more gain, the Grayhawk works better in my room when I have some ambient light. Then there's also a difference in price, but not enough to make price the deciding factor.

I try to post some pictures over the weekend to show some of the differences.

Chris
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post #8 of 14 Old 07-02-2001, 10:00 PM
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I strongly disagree that the difference in price is not a deciding factor. The Stewart screens are a lot more that the Da-lite high contrast. I purchased an electric tensioned Dalite screen cheaper than a Lexus commuincator which is a pull down Stewart model. Hell, you can buy a fixed wall high contrast from Cousinsvideo for 500.00 delivered. I do not think you can buy any Stewart Grayhawks for anywhere near that.

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post #9 of 14 Old 07-03-2001, 09:20 AM
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Bulldogger,

I think he was talking about *his* particular situation... http://www.avsforum.com/ubb/smile.gif I'd have to agree with you that price *is* an issue in most cases.

&lt;soapbox&gt;
However, when you're talking about fixed screens the additional cost for getting a more expensive screen is actually a small part of the total system cost. Don't let the price dictate your buying decision completely, there are differences between screen fabrics and different brands of screens. Take a look and let your eyes decide which is the best value, don't buy the most afforable screen you can find without seeing it first. After spending so much time researching projectors and finding the best deal, I think sometimes we forget the other part of the equation, the projection surface.
&lt;/soapbox&gt;

Regards,

Kam Fung
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post #10 of 14 Old 07-05-2001, 06:10 PM
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Chris,

Can't really help ya' with the DaLite vs the Stewart, but there is something I heard that I thought I'd pass on to ya'. http://www.avsforum.com/ubb/wink.gif

Back at Infocomm JVC had a booth setup with the Grayhawk, promo-ing' it all over the place. Well... Vutec has a new screen coming out that is basically a black screen, has a 60:1 contrast ratio for the screen alone, yet does excellent white levels. They ended up putting the Vutec screen in the JVC booth! http://www.avsforum.com/ubb/rolleyes.gif http://www.avsforum.com/ubb/biggrin.gif

For now though the new Vutec isn't out yet, but I'm being told that they may call it the "Blackstar". As soon as I find out though, or get my hands on one... I'll post here in the forum.

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post #11 of 14 Old 07-06-2001, 03:54 PM
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Eh?

Which INFOCOMM are you talking about? I didn't notice anything like that at the JVC booth. I did see the screen I think you are talking about at the Vutec booth, though. It definitely exhibited some interesting characteristics. It was very dark, but it had a pretty pronounced gain characteristic so it was watchable under bright light. It also had some kind of ridged texture that may help with off-axis light rejection. The fall-off was pretty extreme once you got off-axis though, however within a certain angle it is pretty good.

Definitely an interesting new development, I don't know if it will scale to home theatre screen sizes, it seemed like it was a rigid material and the ridges lead me to speculate that it might be molded.

Regards,

Kam Fung
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post #12 of 14 Old 07-07-2001, 09:19 PM
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Kam,

I have confirmed with more than one source at Vutec that they did show the new screen material in the JVC booth. (although I'm not sure when, and for how long) Also from what I'm told JVC is VERY interested in this new screen from Vutec. http://www.avsforum.com/ubb/wink.gif They will also be showing it at the CEDIA show in September.

I have found out that for now though it's still in the prototype stage but the feedback is very positive indeed. One thing though that they need to work on is the gain. Right now I'm told it has a gain of 2.5! Yikes! http://www.avsforum.com/ubb/rolleyes.gif I would think that once they get the gain down to 1.5 or so then the contrast will be simply amazing! http://www.avsforum.com/ubb/smile.gif

You are right though, in that it is a rigid screen so for those that need a roll-up model it isn't an option. Although Vutec does have nice multi-masking wall mount screens that would be perfect however.

Hopefully I'll get to see it at CEDIA and we'll have more info on it by then.

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post #13 of 14 Old 07-09-2001, 09:54 AM
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Should be interesting, I'd like to get a close look at it. I didn't have much time at INFOCOMM. That screen was *black* off axis, pretty interesting if they can expand the viewing angle and scale up the size. The sample they were showing at INFOCOMM was on a pretty small screen, I'll be interested to see it on a larger one.

Regards,

Kam Fung

[This message has been edited by KFung (edited 07-09-2001).]
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post #14 of 14 Old 07-09-2001, 05:06 PM
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Who cares about tests! lets focus in consumer that purchased
the thing. I have a Da-Mat HC wich I use with my Mitsubishi X400. it is just fenomenal, and the price is graet
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