Ambient light rejecting screens and projector lens shift. - AVS Forum
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post #1 of 4 Old 08-30-2014, 12:15 PM - Thread Starter
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Question Ambient light rejecting screens and projector lens shift.

Hello:

I'm considering to buy a fixed screen with the EliteScreen's CineGrey 5D material. However, I've read that if you have done a lens shift in your projector it may result in a lose of the screen uniformity, becoming a part of the screen darker than the other. Is it right?

Thank you.
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post #2 of 4 Old 09-04-2014, 01:37 AM - Thread Starter
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GranceShin: thank you for your prompt answer .

I found this thread, right in this forum: Has ANYONE tried the Elite Cinegrey 5D screen yet? . I've read that some people feel very happy with this model. However, I don't remember where, I also read that the screen shows some artifacts if you don't set the projector right in front of the screen, in (almost) a perfect perpendicularity.

How did you set up yours? Have you done a lens shift? If so, Was it vertical or horizontal?

Cheers.
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post #3 of 4 Old 09-04-2014, 07:16 PM
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You will get the best performance from the screen by not using any horizontal lens-shift (if you even have it) which means your projector lens SHOULD be centered between the left and right side of the screen. You will also get the best performance if your projector is mounted as far back as possible while still filling the screen (basically the projector is zoomed-out for the smallest possible image and then moved backwards until it fills the screen).

The last part is the vertical lens-shift or offset. If possible you should try to position the projector height so the lens is below the screen's top. Assuming the screen is flat against a wall, the perfect height will have the projector lens roughly 12-18" below the top of the screen and your seated eyes roughly 12-18" above the bottom of the screen.

Doing all this will make sure the brightest part of the screen is the center and not one side. Mounting the projector far back as possible (using zoom to keep the screen-size small) will make the brightness its most uniform. The closer you need to mount the projector the brighter the center will get in relation to the sides and top/bottom..This is a big part of why short-throw projectors and light-rejecting screens don't mix well.
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Simple <$250 dedicated black-fabric theater room, build in a day, takedown in an hour.
Easy $25-40 DIY black/dark-grey ambient-light rejecting screen, grab two things from a local store..mix..roll..done.

Last edited by Ftoast; 09-04-2014 at 07:20 PM.
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post #4 of 4 Old 09-05-2014, 08:44 AM - Thread Starter
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Ftoast: Thank you for sharing that information with me. Taking your advices into account, I guess that choosing a low-profile support for the projector was an horrible decision. Because I needed to do both horizontal and vertical lens shift in order to centre the image :/ . This support doesn't give me much freedom to adjust the projector in the right position really.

With my current 100" screen, made with EliteScreen's MaxWhite material, projecting 14.76 feet away (4.5 meters), I've not noticed that the brightness isn't uniform. Just the contrary. But I guess that if I used that ambient light rejecting screens, the result would be very different. The vertical shift, for example, is very long right now .

GranceShin: Also thank you for your formula. I'm going to note it down, for future reference. Although right now it's impossible for me to apply it, because I've a low-profile support that doesn't allow to lower the projector more. The ceiling in my sitting room is high and the projector is set very close to it. I'll have to consider buying a new support.
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