Gray Screen test help - AVS Forum
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post #1 of 4 Old 11-07-2000, 06:16 PM - Thread Starter
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Ok, I have 2 4x8 sheets of plywood. I divided them in half. One half is white, and the other three are each a different shade of gray. My question is: What should I project onto them. A test pattern or a movie or what? I am a total novice and I am learning a lot from the vast amount of knowledge that flows around hear. Thanks...

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post #2 of 4 Old 11-08-2000, 02:25 AM
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Hi,

I think it is a very bad idea to do a direct comparison, at least not for white. The reason is that your eye adapts to the greatest brightness and white on a gray sample near to a white sample will just look grey.

Beside projecting white and black onto your sample it may be a good idea to project a move which contains high contrast images and images which are overall dark (space scences) and overall bright (outdoor natur in bright sunlight). You may also look only on one of the sample and mask the others black to give the eye time to adapt to this environment. Another problem may be that you probably have to calibrate contrast and brightness for each of the samples separately.

Anyway, you have a lot of testing to do to come to a conclusion.

Emil

[This message has been edited by Emil Naepflein (edited 11-10-2000).]
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post #3 of 4 Old 11-09-2000, 04:30 AM - Thread Starter
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I did the test last night. I kept in mind that the eye "and mind" would always like the lighter brighter picture. I used the Matrix and Total Recall. The first thing that I noticed was at the beginning of Total Recall when they roll the trademark. The background is black with a blue pyramid. It was a great eye opener. The blacks got better the darker the screen. I had an 8x8 screen made up of 4 4x4 test screens. I have it narrowed down to 2 colors. It was the middle hues. About a Dove gray and the other one is a little darker. It really helped the reds and flesh tones. Now my next question is...... I am going to use black and burgundy in my HT, with black around my screen. Considering that black and white levels a perceived. Will a black curtain change the effect? Now I need to go to the fabric store and get some cheep black fabric and check it out... I hope to get some pictures out on my web site soon.

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post #4 of 4 Old 11-09-2000, 08:21 AM
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If you wish to REALLY DO A SERVICE FOR THE FORUM MEMBERS, what you need to do is go to a photo shop, and buy the 20- level grey scale card that is availible from KODAK. it will cst about $12 or so. it breaks up the white-to-black greyscale inot 20 different levels. I think it may be done at 5% increments, but there is no indication of such. I suspect that it would take $30 of long distance calls to Kodak to find that out. There is probablility that no one there will know the answer to that question,as they have been publishing that card for years for photographic use, when developing B&W photos. All the photographer requires is a understanding of the desired results, not a % number. So, no such calibrated scale emerged. I am quite sure that the exact % values a re known by SOMEONE at Kodak, but who really knows.

ALSO, it is critical to state what projector you are using with your particular 'grey' choice. The absolute black level of the projector in question is the reallly important fact here.

Trust me, manufacturers are paying attention, screen and projector, both. What paints you used to get to the Grey you have chosen, and the method of putting it down as well. The fabric you used and/or the base material. This allows one to compensate to get equivalent results.

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