effect of bright corners on contrast - AVS Forum
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post #1 of 20 Old 12-22-2012, 08:46 AM - Thread Starter
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Hey everyone,

I am pretty happy with my new RS4810 but have one question. The unit I have has uniformly bright corners. I do not notice them when viewing most content, only on black or mostly black screens. The only time I have noticed it while watching content is when there is an intro or credits that are white in the middle of the screen. I do not seem to notice on dark screens with other stuff going on. Using the search function here only showed a few examples and the ones posted looked worse than what I have.

My concern is that I wonder if the bright corners reduce the contrast that I could be getting on the screen if they were not present.

Has anyone else thought this through?

AVS is willing to try to work with their supplier to exchange this unit if I can get some good documentation pictures to them but my camera and camera skills don't seem to be up to the task in my opinion. I think I can live with this (and some focus uniformity problems I have) if it isn't a really big problem. My calibrator has recommended I exchange it (of course he wants the best unit to work with), but I don't know if I want to hassle with it. He has not seen the pj in person, only going off of my description.

If the bright corners significantly reduce contrast I would probably go thru the hassle of exchanging it. If it is only an annoyance, I want to just let it go and enjoy the projector.

thanks for any and all opinions.

ed
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post #2 of 20 Old 12-22-2012, 09:45 AM
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Is your projector's placement such that you are zoomed to make the image as large as possible? If so, and if the projector can be relocated such that it is further from the screen--- then the passage of image rays through the lens would be more centered (this might be the root issue) while the smaller aperture might increase contrast as well. Overall luminosity would take a hit. The effect will be diminished as the lamp ages I suspect. Hardly solace.

Sony G90-->D-ILA--> LCD-->Vango LED DLP
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post #3 of 20 Old 12-22-2012, 10:16 AM - Thread Starter
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the lens is located at the farthest point of the sweet spot for a 480 (17'6")

almost minimum zoom
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post #4 of 20 Old 12-22-2012, 10:36 AM
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Quote:
Originally Posted by edfowler View Post

Hey everyone,
I am pretty happy with my new RS4810 but have one question. The unit I have has uniformly bright corners. I do not notice them when viewing most content, only on black or mostly black screens. The only time I have noticed it while watching content is when there is an intro or credits that are white in the middle of the screen. I do not seem to notice on dark screens with other stuff going on. Using the search function here only showed a few examples and the ones posted looked worse than what I have.
My concern is that I wonder if the bright corners reduce the contrast that I could be getting on the screen if they were not present.
Has anyone else thought this through?
AVS is willing to try to work with their supplier to exchange this unit if I can get some good documentation pictures to them but my camera and camera skills don't seem to be up to the task in my opinion. I think I can live with this (and some focus uniformity problems I have) if it isn't a really big problem. My calibrator has recommended I exchange it (of course he wants the best unit to work with), but I don't know if I want to hassle with it. He has not seen the pj in person, only going off of my description.
If the bright corners significantly reduce contrast I would probably go thru the hassle of exchanging it. If it is only an annoyance, I want to just let it go and enjoy the projector.
thanks for any and all opinions.
ed


Ed,


You may also want to consider how good your current convergence is! eek.gif

If you got real lucky with your current sample and your current convergence is considered golden compared to most, you might want to consider living with the bright corners and enjoy the possible great convergence benefits.

It is all about compromise at times and you never know what the next replacement sample may be like! If on the other hand, your current convergence is not so great, it might make even more sense to swap out.... Just some food for thought!


...Glenn smile.gif
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post #5 of 20 Old 12-22-2012, 10:39 AM - Thread Starter
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convergence was off 4 to 6 clicks on the red all over the screen, some places worse than others. blue was spot on
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post #6 of 20 Old 12-22-2012, 11:56 AM
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How much vertical lens shift are you using. Were the red errors vertical or horizontal, that it is up down or left right? See my post in the 4810 thread re my general comments and recommendations.

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post #7 of 20 Old 12-22-2012, 01:22 PM - Thread Starter
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the pj is mounted even with the top of the screen , so about a half a screen's height worth of lens shift. the red errors were 99 % too high in the vertical plane.
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post #8 of 20 Old 12-22-2012, 01:44 PM
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So it looks like CA is a contributng factor. Try as a verifiication using less lens shift which of course will shift part of the image off scrren and see how the portion projected from lens center looks. CA is not a luck of the draw thing. The bigger the lens diameter, the less CA occurs. Its a get what you pay for with less than world class lenses on $3K machines.

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post #9 of 20 Old 12-22-2012, 09:05 PM - Thread Starter
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so I guess I was just spoiled by the lens on my Samsung SP-A800B.
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post #10 of 20 Old 12-22-2012, 09:22 PM
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yea me too but I got a better lens than even that on my 1000ES. remember Joe K on the 800 and 900 provided vertical lens shift but no horizontal lens shift saving customers from horizontal CA. Forced them to mount it in the screen center horizontally. vertical lens shift and its associated CA is a necessary evil for most mounting situations. Also Ed you have no misconvergence with the Samsung because it is a one chipper. smile.gif

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post #11 of 20 Old 12-23-2012, 07:00 AM - Thread Starter
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hmm.... I wonder if I can take the lens off of my 800 and swap it out with the one on my 4810?...



















just kidding cool.gif
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post #12 of 20 Old 12-23-2012, 08:57 AM
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You had me scared there for a moment. It would be nice if projectors all cam with lens mounts and one could buy as good or as poor a lens as one wanted ala a camera with interchangeable lenses. The good lenses are expensive. On bif boy projectors lens are often interchangeable but the choices are not quality based but throw and width based. Of course we know that certain of thodses lenses are better than others.

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post #13 of 20 Old 12-25-2012, 09:45 PM - Thread Starter
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here's what I'm talking about:

DSC00469.JPG 1038k .JPG file
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post #14 of 20 Old 12-25-2012, 09:46 PM - Thread Starter
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Here's what I'm talking about:

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post #15 of 20 Old 12-26-2012, 05:53 AM
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What is that? A black 0% window or perhaps a 20% window? If you aren't joking, I would return the projector. You would have to inject LSD into the projector to get colors like that on a gray window.

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post #16 of 20 Old 12-26-2012, 06:03 AM - Thread Starter
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That is the hide function sp I guess it must be a black window. I have been noticing the bright corners on dark scenes and credits more now that I have watched a couple of movies with it. Either I am noticing it more or it is getting worse. I am not joking
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post #17 of 20 Old 12-26-2012, 06:21 AM
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I do not know what the hide function is. But I have never seen colors like that on a black scrren.

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post #18 of 20 Old 12-26-2012, 06:43 AM
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Welcome to LCOS and SXRD. I have described this at length in previous generations, spoke with JVC engineers about it back then, guess nothing has changed on this front.

What you are seeing is normal, no such thing as bright corners, just bad color uniformity. Some units are better, some worse. It's why I sold my original RS1 way back.

How long did you run exposure on the camera? If you can see this type of discoloration on your screen with hide option (O IRE window) I would try to get it exchanged if you can for a better unit.

Run through grey windows up to 50 IRE and look at color uniformity there, it usually changes at different IRE levels.

Now, if you want pure black at 0 IRE DLP is the only option.
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post #19 of 20 Old 12-26-2012, 11:38 AM
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Quote:
Originally Posted by mbonikow View Post

Welcome to LCOS and SXRD. I have described this at length in previous generations, spoke with JVC engineers about it back then, guess nothing has changed on this front.
What you are seeing is normal, no such thing as bright corners, just bad color uniformity. Some units are better, some worse. It's why I sold my original RS1 way back.
How long did you run exposure on the camera? If you can see this type of discoloration on your screen with hide option (O IRE window) I would try to get it exchanged if you can for a better unit.
Run through grey windows up to 50 IRE and look at color uniformity there, it usually changes at different IRE levels.
Now, if you want pure black at 0 IRE DLP is the only option.

This is bull, if your last LCOS was the RS1 back in the day things have changes since then. And the top LCOS/SXRD beats any DLP in almost every aspect.

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post #20 of 20 Old 12-26-2012, 01:31 PM
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There is no pure black at 0 IRE with any digital projector.

There is absolutely no one beats the other when money is not an bject. There are very nice three chip DC4 machines out there with very good lenses and at the commercial end with enough light to blind you so to speak. LCD no matter the variant, reflective or transmissive, does some things worse and somethings better. Happy Holidays Andreas. Nice to see you posting.

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