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70" XBR2 Screen issue: light Oval Shape around Dark Rectangle

1301 Views 8 Replies 3 Participants Last post by  RobbinMerritt
The attached image is a multi-second exposure so you can see the effect I am discussing on the totally dark screen. It's hard to see normally but I did notice it the first time while watching a movie.

I wonder what this is and will it get worse?

The iris is set to low. Adjusting the iris changes the screen brightness uniformly. The rectangle brightness changes with the rest of the screen. I don't see any color in the shape and I can't see it on any color field besides black or gray (10 IRE).

What within the TV would be this shape? The mirror and the frame of the panels come to mind. What else? I assume this isn't related to the panels themselves as a single panel issue would cause a color blob and it wouldn't be a perfect rectangle.

I also see a bright "race track" shape around the rectangle.

Any ideas what might cause this?
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I saw on owen's posts about dismantling his 70" (to paint the interior) that the lens is masked horizontally with some thick black tape, presumably to reduce light leakage a little. It's not masked vertically.

I'm looking at your image and seeing that the top and bottom edges of the dark area are nice and sharp and straight. The left and right edges are fuzzy and *could* be a little convex, hard to tell.

Of course, then the question is: Why would it be *darker* inside of your shape that mimics the masked opening on the lens? I don't know. It's just a correlation, not a conclusion.

Perhaps it's some sort of secondary reflection inside the lens? The top edge of the rectangle may actually be an artifact caused by the bottom mask, for instance. The lighter area above the rectangle could actually be light that's bounced around inside the lens to the point that it exits from the bottom, is partially blocked by the tape at the bottom, and strikes your screen at the top. Dang, I should just draw this or something. I'm not explaining it very well. Let's see...

Okay, a very craptacular diagram should be attached. Sorry it's so bad, I only have mspaint available to me at the moment.

Note that extra light could be coming from something other than internal reflections in the lens. It could be leaking around the side of the LCoS panels, or around some other element of the optical block. This is just a general idea of something that could satisfy my theory...
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You actually draw a diagram for me and apologize for the quality. I have to chuckle. I appreciate the thought you put into this!

Your theory seems sound to me.

For me, the exact rectangle shape is the interesting part. I assume that the "effect" is actually the oval shape. For the most part, the middle rectangle is the same level of black as areas outside the oval (except for the very top of the screen, which has always been a bit lighter). Since the effect is dimmed by the iris, I have to assume the light output of the OB is the source -- whether its generated inside the OB or reflection from light once it leaves the lens (as you suggest) is unknown.

After the light level gets high enough, I can't see it. So any color field besides 10-15 IRE gray doesn't show it.

I assume you don't see anything like this on your XBR2?
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I haven't looked. I'm not sure I want to know if it does it.
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I wonder if this isn't caused by the lamp and/or the lamp reflector. The TV has always had a hot spot in the middle:

But when I edit the dark and gray screens together, I can see that the rectangle is visible in the bright middle of the gray screen (the camera turned it a bit blue).

It is visible in all color fields, if I reduce the picture level low enough.

Maybe this has always been present and I simply never noticed it before. Or perhaps as the lamp has aged the effect is more visible (whether it's the lamp or a reflection, different output levels from the lamp could still change the visbility of the effect).
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It must be leakage from the lamp, because blocking more light with the lcos panels (a.k.a. displaying a darker image) doesn't seem to affect the intensity of the artifact. If you have auto iris on, that ought to affect it as well, but it doesn't look that way to me. It just looks like a constant amount of extra light overlaid on whatever the image is.

Maybe you need to go to the extra lengths owen went to to block the leakage in the floor of the rear projection area.
I agree that the panels don't seem to affect the level of the effect. However, the iris does affect it. So does power saving mode. And it's not caused by the lamp or the lamp reflector, clearly.

I also find that the oval shape is visible in any color field, provided I lower the picture setting low enough (around 5). And the oval is always a slightly brighter version of the same color. When I raise the picture level enough, the image light masks the effect. That suggests that all three light paths are equally affected.

I wonder if it might be a weakness in the polarizing filter. Or some light is by-passing it. Un-polarized light would pass through the LCoS panels unblocked.

I'm going to watch the effect and see if it gets worse. I know for sure it was present 6 months ago (I saw part of the oval on a star field but thought it was a part of the image) and maybe longer.

I find it hard to believe that I'm the only user on this forum who has noticed this (or has the problem).
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didn't you have your set calibrated by umr? may want to contact him to get jeff's thoughts

Originally Posted by mr. wally /forum/post/12909688

didn't you have your set calibrated by umr? may want to contact him to get jeff's thoughts

Good memory! Yes Jeff did my set -- his first XBR2. I did contact him but he didn't have any suggestions.
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