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LCoS dis-uniformity- Is this variable with use and conditions?

post #1 of 14
1/9/07 at 7:34am
Thread Starter 
I've heard the terms white field uniformity and color uniformity and not sure if they are interchangeable or not.
In any case, I mean the presence of faint clouds of certain colors, usually green or pink/magenta, most noticeable when viewing B&W content.

I'm curious if the noticeability of this condition is affected by things like operational temperature, room temperature, bulb aging- or any other variable.
I've got about 140 hrs on my Pearl now, and it seems that if I run the unit about 2-4 hours before I try watching any B&W content, then the appearance of the greenish cast I was getting in one quadrent of the screen seems to be greatly diminished.
In fact, I had finished up a color feature one night, and was going thru the discs special features and after about 5 or 10 minutes I realized that I was looking at primarily B&W content (a doc using a lot of B&W pictures) and yet it never dawned on me that I wasn't seeing any uniformity issues until it was almost over. I was wrapped up in the content that I didn't even notice to look for a problem, and then after I realized this and did try to look, it seemed like I had to strain to see it (truly pathetic I know...going looking for trouble).

I don't want to jinx myself, but is this something that actually can improve with use- and if so - can it also get worse?
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post #2 of 14
1/9/07 at 8:37am
I talked about this with Joseph Chen of Cinetron after I saw the CEDIA demo Pearl's nonuniformity that seemed to be more marked after hours of use. He said heat does have a role.

I've seen my Pearl's nonuniformity problems become less severe over a viewing session, becoming less noticeable, after an hour or so. (I've spent hours doing the 3D Gamma adjustments and the nonuniformity is much less apparent.)

Dan
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post #3 of 14
1/9/07 at 9:12pm
I am surprised that more people don't see this. Maybe it's like rainbow effect, some see it and some don't. I had an SXRD rear projection many months ago that had this non uniformity so bad that black and white was unwatchable. A repair [new light block] left the set worst than before the repair. Sony was very cool and offered full credit toward something else. I went with the Pearl. I love the PJ, it is much sharper than the RPTV and feels much more like a real home theater.

I have about 75 hours on the bulb and have always seen about the same amount of lavender discoloration in the center of my picture, especially noticeable in gray scale. It's much less of a problem than with the XBR. I really hope that some callibration down the road will make B & W [much of my collection] more watchable. Until then I watch color in amazement at the quality of the image for the price.
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post #4 of 14
1/13/07 at 1:43pm
Quote:
Originally Posted by sayitisntsony View Post

I am surprised that more people don't see this. Maybe it's like rainbow effect, some see it and some don't. I had an SXRD rear projection many months ago that had this non uniformity so bad that black and white was unwatchable. A repair [new light block] left the set worst than before the repair. Sony was very cool and offered full credit toward something else. I went with the Pearl. I love the PJ, it is much sharper than the RPTV and feels much more like a real home theater.

I have about 75 hours on the bulb and have always seen about the same amount of lavender discoloration in the center of my picture, especially noticeable in gray scale. It's much less of a problem than with the XBR. I really hope that some callibration down the road will make B & W [much of my collection] more watchable. Until then I watch color in amazement at the quality of the image for the price.

Color and brightness non-uniformities in 3x LCD and 3x LCoS projection systems are a known problem. Silicon Optix has just launched a chip called the Geo (Geometry Processor) that will correct for these effects as well as several others. Here's a link to the press release:
http://www.siliconoptix.com/chipProd...09D6E6F457D6FF

The chip was demo'ed at CES last week. I took pictures of the simulated color non-uniformities that were generated by the chip on a white field at 1080p resolution. They look remarkably like what I've seen on many production projection systems. The idea is that if the chip can generate the non-uniformity, it can also generate the correction for an existing non-uniformity.
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post #5 of 14
1/13/07 at 4:28pm
This is definitely NOT like rainbows. Everyone can see it (unless you are color blind), but not all displays, even those of the same make and manufacturer, have it to the same degree. The LCoS and LCD projectors seem particularly prone to this, and I don't know why.

Sony's custom gamma tool allows you to correct a lack of color uniformity, though it's a severe pain to use.
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post #6 of 14
1/13/07 at 9:08pm
LCOS panels are non uniform. I'm told this is mostly due to varying thickness.

Sony's custom gamma tool does *not* allow you to adjust this. Perhaps you were thinking of the service menu?

There are 2 issues to uniformity - light output and color. Non-uniformity in either gives our brain clues that the image is being projected on a screen, rather than real. Color non-uniformity would seem to be worse for this. Like everything else, some people are more sensitive to this than others. Color non-uniformity is obviously much more visible with black and white content.

I have developed a tool which adjusts the uniformity tables accurately, using a 16 bit astronomical CCD camera. I've been working on porting it over to the Pearl and it is close to being ready.

Apparently, from what I've seen in several Pearl's now, Sony has decided to do their factory calibration by adjusting red and blue only. The uniformity data for green is all zeros at all levels in every Pearl I have checked so far. So that means they are calibrating for uniform color but not for uniform light output. I guess Sony decided that's all you get at this price.

William
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post #7 of 14
1/13/07 at 9:17pm
Hi William. I was wondering if the JVC HD1 sample you had (was this a pre-production unit?) showed the brighter corners on an all black screen similar to what the Pearl/Ruby show on an all black screen? Apparently a few people noticed this on the RS1 demo at CES, but it was not at all present on the HD1 downstairs. Any idea why this would be, or do you happen to have any info on this?

Thanks
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post #8 of 14
1/13/07 at 9:47pm
Thread Starter 
Toe,
at least as far as the Pearls that I have seen, the issues of brighter corner visibility is the same as uniformity and convergence- it varies from unit to unit.
The Pearl I ended up keeping does not have an issue with corner brightness-believe it or not.

I will be very impressed if the JVC, at these similar price points, are varying substantially less from unit to unit.
I guess we will just have to wait and watch thru March to see what kind of feedback is coming in from the hundreds of users with unique units, and not just hundreds of spectators watching the same units.

For the people so inclined, I'm glad that Mr Phelps will be able to offer some kind of solution to this, but for me (and my budget) it seems like an awful big hassle and inconvience. Probably more of an inconvience than just having to wait till the second or third hour of a marathon viewing session to watch any B&W content.

Also, I would be very concerned as to how long these adjustments would hold- hence my original query in the first post. Is this a problem that is going to change over time? Is there drift possible in the location, intensity, or mass of the discoloration?
The Pearl is my first experience with LCoS- whether I keep it or upgrade to the JVC these are still concerns that I will have with this technology.
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post #9 of 14
1/13/07 at 10:11pm
It's too soon to tell if the new JVC's will have this issue. I have only tested one sample. At full black, once one gets dark adapted, it does appear to have some brightening in the corners, but it does not look to my eyes to be anything like what I've seen in Ruby's. I did not have to wait for dark adaption to see it on the Ruby.

As far as I know this is primarliy an optical issue, and not one that can be corrected by any adjustments in the projector.

Uniformity on the recent JVC projectors, especially the HD10K, has been very stable, even with lamp changes. However, it is important to realize that the HD1/RS1 is a very different design, so we do not know how stable it will be.

William
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post #10 of 14
1/13/07 at 11:13pm
Thanks for the response. IF it does have it, atleast it sounds like there is a good possibility that it will be better than it is on the Pearl/Ruby.
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post #11 of 14
1/13/07 at 11:23pm
Quote:


Sony's custom gamma tool does *not* allow you to adjust this. Perhaps you were thinking of the service menu?

Yes, the special gamma adjustment in the service menu allows for RGB adjustments for over 200 points at several levels of brightness.
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post #12 of 14
1/13/07 at 11:26pm
Quote:
Originally Posted by TomHuffman View Post

Yes, the special gamma adjustment in the service menu allows for RGB adjustments for over 200 points at several levels of brightness.

Right, but you said "Sony's custom gamma tool", which is called Image Director, and that does not allow adjusting of the "3D Gamma" tables. They can be accessed via RS232, and on the Ruby via TCPIP.
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post #13 of 14
1/14/07 at 12:47am
Thanks for the info Paulidan. I was not aware that the corner brightness issue varied from unit to unit like conv and uniformity. I guess we will just have to wait and see how the JVC does.



Quote:
Originally Posted by Paulidan View Post

Toe,
at least as far as the Pearls that I have seen, the issues of brighter corner visibility is the same as uniformity and convergence- it varies from unit to unit.
The Pearl I ended up keeping does not have an issue with corner brightness-believe it or not.

I will be very impressed if the JVC, at these similar price points, are varying substantially less from unit to unit.
I guess we will just have to wait and watch thru March to see what kind of feedback is coming in from the hundreds of users with unique units, and not just hundreds of spectators watching the same units.

For the people so inclined, I'm glad that Mr Phelps will be able to offer some kind of solution to this, but for me (and my budget) it seems like an awful big hassle and inconvience. Probably more of an inconvience than just having to wait till the second or third hour of a marathon viewing session to watch any B&W content.

Also, I would be very concerned as to how long these adjustments would hold- hence my original query in the first post. Is this a problem that is going to change over time? Is there drift possible in the location, intensity, or mass of the discoloration?
The Pearl is my first experience with LCoS- whether I keep it or upgrade to the JVC these are still concerns that I will have with this technology.
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post #14 of 14
1/14/07 at 8:43am
WM-

If you're keeping a list of Pearl owners that want uniformity adjustments when your tool is complete please place me on it. I would gladly send the PJ away for a couple weeks if it could come back with this only flaw fixed or reduced.

Spaciba, Hans
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