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Discussion Starter · #1 ·
Last night I borrowed a CTX DLP projector from a friend who works at a school district. I can't remember the exact model number at the moment though, I'll look when I get home if that's important.


The picture on the projector was very nice, I had it running through my Athlon with dscaler at 1024x768 native resolution on a 60" wide 4:3 screen. I had some "jerkiness" but I think that was being caused by the PC not by the projector. I could see the rainbows, but it was mostly when I would move my head, or if I was walking through the room while the projector was going. In any case, they didn't bother me or my wife which is the important part.


The biggest problem I noticed with the projector was that it threw out a lot of extraneous light. there are 2 vents on the sides of the projector throwing light out into the room, in addition to extra light being thrown out towards the screen.. there was a border around the main viewing area about 6 inches wide that was just white light.. .I think this also affected my black level on the screen as night scenes (we watched the Tombstone Directors Cut) seemed very washed out. I haven't calibrated the HTPC or the projector with Avia yet though, but I'm usually pretty good at "eyeballing" the picture to get it good enough.


Anyway, I was wonder if this extraneous light coming from the DLP was a symptom of this particular projector, or is it something to worry about on ALL DLPs? If it's all DLPs, I may end up looking at a used CRT projector instead of DLP when my big purchase comes :)
 

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The border around the image is one of the faults with DLP (halo). Usually resolved by masking either at the lens with borders or at the screen. As far as light leakage goes, the is a design flaw of the projector. Some projectors are better than others.
 

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Discussion Starter · #3 ·
Is it possible to mask this at the lens optical layer? with a small square metal mask inserted in front of the lens for instance? (old 16mm projectors use a metal mask for the film frame in a similar fashoin, but behind the lens)


is it also possible to put some sort of cloth over the light emmitting grills in the projector that would allow airflow but not allow light (not sure what kind of cloth might do that)


Can anyone recommend a DLP projector that doesn't do this very badly?
 

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Wouldn't a hushbox provide some assistance in preventing light from the air vents from escaping forward towards the screen?
 

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The light leakage you encounter is not a DLP phenomenum, it is common with projectors designed for the business rather than the HT market. My Marantz DLP has virtually no light leakage.
 

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xeyes,


Oops, I forgot, "Welcome to the forum!".


Masking at the lens will not work with the results that you desire. Reason being that light at the lens it not focused and will produce a haze around your resulting image at the screen. Just put your finger in front of the lens and you will see what I mean. To some extent it works, but not with the best results. It really is best to mask and frame your image at the screen. The only other option is to open your projector and mask right at the DLP chip. Keep in mind that you will need accuracy to the smallest fraction of a millimeter for perfect results.


I don't see rainbows, so the halo was my biggest beef with DLP. Again, no projector is perfect. But now that I have masked my screen, I really don't even notice the halo anymore. Check out my 66" DYI screen: http://www.jcgamebooks.com/theater.htm. And if you are curious, the reason for the halo is that it is an unused portion of the DLP chip.


I have owned two projectors thus far. The LP340 and the LT150. The LT150 is really good at not allowing light spill. There is a ring the shoots out from the top (bottom in ceiling mount position), but it is so far from the projected image that it really isn't noticable. Projectors that don't have front mounted grills are usually good at preventing light spill. My LP340 was not good at this.
 

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Discussion Starter · #7 ·
Ah, okay, I understand. Well, masking at the screen isn't really an option as I have a pull down screen. (It's a Bretford Monitor Series I got from the school district, but hey, it was FREE! so I'm not complaining)


Unless someone has ideas on how to do masking on a pulldown screen.
 

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I have two pulldown screens - one is 4:3, one is 16:9. Both are Dalite Model B's. I have them hanging from the ceiling about 1 foot from the wall, and the wall happens to be a dark color. So most of the light leakage I have is diffused by the time it hits the wall, and it's not really noticeable. When I ordered my 16:9 model B, I also had them add an extra 8-9" of blackout material to the top and bottom, which is basically built in masking. Looks great!
 

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I built a wood frame and stapled black velvet that hangs in front of my screen to mask 2.35:1 material. I hang it behind the screen for 1.85:1 and it works perfectly.
 
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