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Thread: Projector "glow" while black?

  1. #1
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    Default Projector "glow" while black?

    I plan on having a projector in my display this year aimed at the inside of a window. I purchased a cheap one, but it had a severe issue. On a totally black screen, tons of light still bled through the LCD and it made my window glow quite a bit. It literally just looked like lights were on. While playing actual video, it's good enough, but I plan on actually having it off for 90% of the show and using it only for specific effects.

    What have you guys done to combat this? Also, could anyone recommend an affordable projector based on first hand experience for our application?

    Thanks!

  2. #2
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    Default Re: Projector "glow" while black?

    My understanding of that problem is the only good solution is to go to a black screen to project onto. I have seen demonstrations of this in home theaters for example showing how a 'white' screen reflects the light that is still coming through a projector.

  3. #3
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    Default Re: Projector "glow" while black?

    Solution 1, buy a better projector. Youíll need a 3 chip dip projector to not have that problem. But those are very expensive and power hungry. So donít even bother down that path.
    Solution 2: mechanical shutter. Search for a mechanical dmx shutter online. I canít recall the name, but thereís a little company that makes these for exactly this purpose. Itís a little metal flag on a motor that literally covers the lens when triggered by a dmx signal. It should be easy to DIY but look for the product online first so you can get ideas.


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  4. #4
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    Default Re: Projector "glow" while black?

    Engineering Solutions Inc. makes several shutters with varying features and prices. They are aimed at the live production industry so priced higher than DIY solutions but they are solid. I use one of their Decabox units to tame some DMX fixtures with non-compliant timings and also used it to send RS232 to a projector based on DMX values (in the days before FPP). Their website is: http://response-box.com
    Last edited by smccoy; 11-03-2017 at 11:06 PM.

  5. #5
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    Default Re: Projector "glow" while black?

    That's the one I was thinking of. It's one of those small companies that makes some specialty gadgets that everyone has. But it's such a generic name you can't remember it.

    I also use their RS232-DMX box when I need to control DMX lights from a room automation system. It's rock solid.

  6. #6
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    Default Re: Projector "glow" while black?

    Iíd invest in a higher end projector. My Nec V260X looks perfect on the windows (but donít buy that model, itís outdated).


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  7. #7
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    Default Re: Projector "glow" while black?

    the NEC NP-V260X is still only a single chip DLP projector. It only has a contrast ratio of 2000:1 It's still going to have a lot of that light spill while it's black. I'm not saying it's not acceptable for many cases. But if that "light in the darkness" is a problem, you need to get into a whole different realm to get rid of it. That's not just the jump from a base level consumer projector to a entry level business model. You'd need to get into the pro realm to get to that point. Here's a search that shows the least expensive projectors currently in this category. I've got some of these and their bigger cousins in my inventory and use them on shows all the time. They'll definitely do the job. But even I wouldn't set one of these in my front yard for a month.

    Since not too many DIYers are going to drop 15k for a projector on their lawn, you're best off either hiding that light spill when you're not using it with a shutter. Or finding ways to mask that spill with other light.

    In my show, I don't project onto things, I project thru them. (not technically, but it's easier to understand that way) For example, I've got tree cutouts with screen material stretched across a frame. The extra light that doesn't hit the tree "screen" buries itself into the ground from an angle that the audience can't see. I always make sure to cast that waste light into the sky, or onto the ground in a way it's not noticeable. I don't allow it to draw a box on a surface in front of the audience.

    Another way to deal with it is to make sure your projector is projecting large enough to fill the whole surface that it's lighting up. If you're projecting onto your house. Make sure it fills that whole elevation of the house, and the other matching elevations have the same ambient light level. That way it's there, but it doesn't stand out because the whole house looks the same. This may require a brighter projector than you have. But those are a lot cheaper than the ones in the link above.

    If you must have that box of light showing, try masking the edges with floods or other lights so that the box border doesn't show as obviously.

    I use Panasonic D series projectors in my display. I've got some PT-D4000s, one DW5100 and a few DW6300 units. I got them all used with lots of hours on them. They have a built in mechanical shutter so you only see any light at all when I want you to. They also have a bunch of other features that make them particularly nice for creative architectural projection such as edge blending and geometry correction and interchangeable optional lenses.

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