Rainbow Effect on Panny PX50 Plasma - is sub-pixel controller to blame? - AVS Forum
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post #1 of 140 Old 05-17-2005, 01:45 AM - Thread Starter
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I have had my Panasonic PX50PXU for a little over a week now, and not long after it arrived I started seeing the dreaded Rainbow Effect on the set. Yes, it IS RBE. I know this is supposed to be an issue that only affects DLPs, but apparently I can see it on this plasma as well. I had a DLP for about a week and a half, and I returned it due to RBE, so I know exactly what it looks like. I also had an RP LCD which had NO rainbows. The effect on the plasma is exactly like the DLP rainbow effect, quick flashes that show up during high contrast scenes with sharp edges; it's an obvious optical effect, not an effect on the screen. There is one difference though, on the DLP I saw the usual three color rainbow. On this plasma I only see yellow flashes. Nevertheless, they are just as distracting and annoying.

I've tried to figure out how a plasma could produce RBE, since I'm sure if this was a normal plasma problem someone else would have seen it by now. The one thing that's different about the new Panasonics are the sub-pixel controller, so I am suspecting SPC may be the culprit. I don't know exactly how SPC works, but I found the following blurb on Panasonic's UK site:

Panasonic UK Viera link

Seamless lines for a superior picture

The new TH-37PE50 and the TH-42PE50 offer seamless lines that allow pictures to look more refined than ever before. The VIERA's Sub-Pixel controller eliminates jagged or blurred diagonal lines to produce smoother, more defined contours to shapes, resulting in a picture that is second to none. Conventional systems process the RGB signal together, but the Sub-Pixel controller processes each colour separately, thus generating crisper, more natural looking images that are sure to impress.


Though it doesn't go into detail, the bolded section above mentions processing each color separately, which could certainly introduce time delays that might affect each color differently, thereby causing them to separate the same way the DLP color wheel does. The flashes I see are yellow, which suggests that red and green are synced (combining to produce yellow) but blue is not.

Does this sound plausible? Is there anything else that could cause rainbow-like flashes like I've described? Has anyone else seen this, or am I lucky number one? And most importantly, does anyone know if SPC can be turned off in the service menu? Obviously, if it can't my only other option is to exchange for a model without SPC and hope that's where the rainbows/flashes are coming from.

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post #2 of 140 Old 05-17-2005, 06:17 AM
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Hm, I haven't notice anything like a RBE on my 50px50.
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post #3 of 140 Old 05-17-2005, 07:16 AM
 
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I haven't either.
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post #4 of 140 Old 05-17-2005, 07:37 AM
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When I was checking out the PD50 model at CC I noticed some strange artifacting when I looked downward and at an angle. It almost looked like a moire effect when you see thin horizontal lines on a NTSC display. Not sure if this is similar to what you were seeing.
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post #5 of 140 Old 05-17-2005, 09:16 AM
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Rainbows are not possible with Plasma. Its an issue with color wheels or systems that paint the screen with one color at a time.

Are you sure its not false contouring? Here is what RBE looks like

!What do rainbows look like from a DLP unit?

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post #6 of 140 Old 05-17-2005, 09:36 AM
 
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Quote:
Originally posted by MathewM
When I was checking out the PD50 model at CC I noticed some strange artifacting when I looked downward and at an angle. It almost looked like a moire effect when you see thin horizontal lines on a NTSC display. Not sure if this is similar to what you were seeing.
Would you normally be watching TV this way?:confused:
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post #7 of 140 Old 05-17-2005, 09:59 AM
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Quote:
Originally posted by optivity
Would you normally be watching TV this way?:confused:
No but it's something I noticed. I would say it's similar to those who dart their eyes around the screen looking for rainbows on a dlp set. It's not how you typically watch tv but we're all anal in that way.
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post #8 of 140 Old 05-17-2005, 10:55 AM
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Rainbows are probably the wrong descriptive phrase for what you are seeing. It reminds me of the discussions from the past about green phosphor latency [more so on the Pioneers]. One interesting comment in these archived discussions, was from an ISF guy that if the artifact was red, blue or purple related, that meant the contrast was set to high.There are other issues discussed, as well, and attached jpg examples of symptoms, etc. [high contrast black box with dimmed white background, etc].

May or maynot be an issue, but so far you have only partially described the symptoms, conditions or the factors of occurance.

http://archive.avsforum.com/avs-vb/s...ghlight=trails

http://archive.avsforum.com/avs-vb/s...een+AND+trails

http://archive.avsforum.com/avs-vb/s...hreadid=217291

http://archive.avsforum.com/avs-vb/s...threadid=94378
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post #9 of 140 Old 05-17-2005, 12:22 PM
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Some people see rainbows looking at street lights - that doesn't mean the street light is defective, it means the person has a visual problem they need to have checked by an ophthalmologist.

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post #10 of 140 Old 05-17-2005, 01:48 PM
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Quote:
Originally posted by dsmith901
Some people see rainbows looking at street lights - that doesn't mean the street light is defective, it means the person has a visual problem they need to have checked by an ophthalmologist.
I thought the same about myself (and the aging eyes) - when considering DLP and concern about rainbows. See if you can find a similar real world condition if you also see these issues.

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post #11 of 140 Old 05-17-2005, 02:32 PM
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I noticed the same thing the other evening on my 42PX50U, empire. I have a DLP front projector in my video room, so I'm familiar with the rainbow effect, which I notice occasionally, but which doesn't bother me at all. Like you, I was surprised to see a very similar effect on the Panasonic plasma which produces a yellow or green flash. Now that I've seen it, I can produce the effect at will by darting my eyes rapidly from one side of the screen to the other during a scene of high contrast. Mostly I don't notice it, and as with my DLP, it doesn't bother me at all
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post #12 of 140 Old 05-17-2005, 02:35 PM - Thread Starter
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I knew when I posted this there would be a lot of doubt, so let me be clear about a few things:

1) I know EXACTLY what the rainbow effect looks like. I owned a DLP RPTV for a week and a half before returning it due to RBE. I have never seen RBE on an RP LCD, on my LCD flat panel monitors, or on a CRT. I have never seen RBE in “real lifeâ€, looking at a streetlight, at car headlights, or anything of that sort. I have seen this effect exactly TWICE in my life: watching a DLP RPTV, and watching this Panasonic plasma. The effect is like seeing flashes in your eyes, the closest description I can give is that I imagine it must be similar to the flashes some people with epilepsy report seeing. I only see these flashes watching these particular kinds of TVs, so I don’t think epilepsy is the cause (unless all DLP rainbow sufferers are actually epileptics).

2) The effect on the Panasonic plasma I am seeing is EXACTLY like the RBE effect on DLP, with one exception: the flashes are all yellow, instead of having three separate colors. It is an optical effect; it is not a screen artifact or motion artifact. I can reproduce the effect the same way as on a DLP, by pausing on a screen with high-contrast or white-on-black content and moving my eyes back and forth quickly. No, I don’t watch TV that way, but I don’t need to do anything special to see the effect during normal viewing. Some people are more prone to RBE than others, and I’m one of those (if I weren’t I’d still have a DLP). It is NOT a subtle effect, at least not in my case. When rainbows show up, they can make a TV unwatchable.

3) I believe that plasmas, in general, are not susceptible to RBE. That is why I suspect there is something unique about the Panasonic that is producing this effect, and that is why I think sub-pixel control may be the cause. DLP color wheels produce rainbows because the each color is displayed separately as the wheel spins, rather than simultaneously. According to the brief SPC quote in my OP, SPC processes each color separately. If any delay is introduced during that processing, then like a color wheel the colors would not be displayed simultaneously. The difference in time between displays of separate colors would be similar to a DLP, and that is why I suspect sub-pixel control is a possible cause of the effect I’m seeing.

I can tell you that I have no doubt whatsoever that I AM seeing RBE on this Panasonic plasma. I’m not imagining it, I don’t have epilepsy or visual impairments, and I’m not misinterpreting some other kind of artifact or issue. I know exactly what I’m seeing. What I’m trying to figure out is WHY I’m seeing it. It’s possible that my set is defective and there is a problem with the color processing that is causing the effect. It’s possible that sub-pixel control is producing the effect. If SPC is to blame, I’d like to find out if that’s something that can be turned off, perhaps in the service menu, because that’s the only way to find out if it is the cause. I’d happily turn off SPC if it got rid of the flashes, because otherwise this TV looks fantastic. I guess I’ll have to contact Panasonic and see what they have to say.

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post #13 of 140 Old 05-17-2005, 02:47 PM - Thread Starter
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Quote:
Originally posted by jacx
I noticed the same thing the other evening on my 42PX50U, empire. I have a DLP front projector in my video room, so I'm familiar with the rainbow effect, which I notice occasionally, but which doesn't bother me at all. Like you, I was surprised to see a very similar effect on the Panasonic plasma which produces a yellow or green flash. Now that I've seen it, I can produce the effect at will by darting my eyes rapidly from one side of the screen to the other during a scene of high contrast. Mostly I don't notice it, and as with my DLP, it doesn't bother me at all
Thank you. It is nice to have some confirmation, on the odd 0.0001% chance that I was losing my sanity. Unlike you, unfortunately, I am very sensitive to RBE and when it shows up it pretty much ruins my ability to watch the set. I gave up on DLP altogether after the DLP rainbows hit me, and I figured I was safe with plasma. It was definitely a big surprise to me also when I started seeing it on the PX50 too. Just my luck I'd end up with probably the first plasma to suffer from this effect.

I'm holding out hope that SPC can be disabled in the service menu, since I'm about 70% certain that is the source of the effect. I'll post whatever I find out about it here.

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post #14 of 140 Old 05-17-2005, 03:28 PM
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Quote:
Originally posted by empire_of_one
I'm holding out hope that SPC can be disabled in the service menu, since I'm about 70% certain that is the source of the effect.
Does this happen with all video sources? Many DVD players exhibit a chroma delay problem that might manifest itself as something like this. I really don't see how SPC could have anything to do with it, since each scanline is being scanned in 1/60/768 seconds, which is only 22 microseconds, far below the human visual system's ability to detect, and as far as I know, SPC is entirely a line-by-line thing.
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post #15 of 140 Old 05-17-2005, 06:54 PM
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Empire,
I have not seen the "rainbow effect" on DLP's but I have seen yellow falshes on the Panny. This does not happen frequently.

Please keep us posted with your findings and hopefully SPC may be turned off somehow as well as tweaking the yellows further.
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post #16 of 140 Old 05-17-2005, 07:13 PM - Thread Starter
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It happens on all sources. I don't have HD yet, but on DVD and on SD via DirecTivo it's there. How much it shows up depends on how much high-contrast material there is on screen. I can only guess that SPC may have something to do with it, but no way of knowing yet.

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post #17 of 140 Old 05-17-2005, 10:05 PM
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I see it a little bit on most plasmas if I scan my eye quickly across the screen. It is NOT the same as the DLP rainbow effect, no where near as annoying, but it is there pretty much on all plasmas, some being worse than others.

I wondered if it would be an issue when I bought my panny over a year ago, but I guess I got used to it because I just don't notice it anymore.

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post #18 of 140 Old 05-17-2005, 11:28 PM
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Quote:
Originally posted by empire_of_one
... On this plasma I only see yellow flashes. Nevertheless, they are just as distracting and annoying.
Empire – if what you are seeing is what I have seen, you are absolutely correct! It will appear as a flash but only when there is a significant change in the overall display density, such as there would be with any motion in a high contrast image. It will also happen on a low contrast images if something dark occupies a significant portion of the display, thus changing the overall density. If we are talking about the same thing, it will be most obvious in the black/dark areas, as they will appear lightened momentarily.

I was watching a close-up scene, on one of those plasmas, where two dark haired people were having a conversation. As one person talked, their hair would move and the screen would flash. The whole scene produced a series of strobing.

I am aware of other models of new Panny displays being placed by Panny because of this problem. You should contact Panny asap.

I don’t have a clue about the RBE, tho when I sneeze on my CRT I can see a whole bunch of little rainbows looking back at me. :D
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post #19 of 140 Old 05-18-2005, 05:43 AM
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Strangely I've seen rainbows on a rear projection CRT. I don't find this all that unusual because CRT's use a RGB gun to project the image. Bottom line is that every sort of display is going to have some sort of anomaly that is going to be more annoying to some than others. Like anything else, it's a compromise. It's definitely not something I fret about.
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post #20 of 140 Old 05-18-2005, 05:49 AM
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Quote:
Originally posted by MathewM
Bottom line is that every sort of display is going to have some sort of anomaly that is going to be more annoying to some than others. Like anything else, it's a compromise. It's definitely not something I fret about.
Well put.

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post #21 of 140 Old 05-18-2005, 06:35 AM
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At the bottom of this link is a description of the sub-pixel controller.

http://www.panasonic.ca/english/audi...asma/viera.asp

I don't see how this could cause a rainbow effect.
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post #22 of 140 Old 05-18-2005, 07:44 AM
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empire - if you suspect the SPC as the reason for the RBE, have you tried viewing other plasmas (non-Panny, or pre-8th gen Panny) to see if they exhibit the same phenomenon?
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post #23 of 140 Old 05-18-2005, 08:40 AM
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Quote:
Originally posted by MathewM
... every sort of display is going to have some sort of anomaly that is going to be more annoying to some than others. Like anything else, it's a compromise. It's definitely not something I fret about.
I don’t agree. I think I can go along with ‘every sort of display technology is going to have some sort of trade off’, but the problem that is the subject of this thread is better described as a defect. It is does not happen with all Panny panels, only some. As I mentioned above, in certain situations, depending on the scene being displayed, the plasma can create a strobing effect that is not otherwise present. When it happens, the distraction is bad enough the display is virtually worthless.

It's not a quick flash. It is akin to having the brightness adjustment suddenly kicked up for about 1/4 sec, then the display returns to normal. It is definitely something anyone should fret about.

Btw, Empire, if what you are experiencing is the same thing, it will happen with all std inputs; composite, component, s-video, and VGA.
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post #24 of 140 Old 05-18-2005, 09:46 AM - Thread Starter
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It's not a quick flash. It is akin to having the brightness adjustment suddenly kicked up for about 1/4 sec, then the display returns to normal. It is definitely something anyone should fret about.
This is not the same thing that I'm seeing. They are quick flashes generated by bright whites/yellows against a dark background. It happens on a live moving scene, or a paused scene. If you have seen RBE on a DLP before, it's exactly the same except it's only yellow instead of three colors.

Quote:
empire - if you suspect the SPC as the reason for the RBE, have you tried viewing other plasmas (non-Panny, or pre-8th gen Panny) to see if they exhibit the same phenomenon?
Well, I've watched a lot of plasmas in store environments, and I've never seen it there. But I've also never seen RBE on a DLP or on this model of plasma in the store either, only when I get it home and watch in a normal environment. RBE in general seems a lot harder to see with all the bright ambient light of a showroom.


Quote:
At the bottom of this link is a description of the sub-pixel controller.

http://www.panasonic.ca/english/aud...lasma/viera.asp

I don't see how this could cause a rainbow effect.
The link describes how each RGB dot per pixel is processed separately, which concurs with the previous blurb I read. I still believe that this processing could cause one of those dots to "fire" slightly behind the other two, mimicing the way DLP color wheels produce time differences between the time that each color is rendered. I can see rainbows on an HD3 DLP chip with a 7-segment color wheel spinning at 9600 rpm, which works out to each color of the wheel being "flashed" 1120 times per second. So the time difference between consecutive color wheel segments "firing" is approximately 0.0009 seconds. That's all the time difference any processing would have to introduce to reproduce the effect. Since I've never heard of RBE-type effects on other plasmas, I am only guessing that the SPC that is unique to the Panny could be introducing that delay. It could easily be something else too though.

If anyone's ever seen RBE-like effects like what I've described on other plasmas, I'd definitely like to hear about that. I'm hoping it's a Panny-specific issue so that if it can't be resolved somehow, I can at least consider other plasmas.

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post #25 of 140 Old 05-18-2005, 11:00 AM
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Quote:
Originally posted by empire_of_one
The link describes how each RGB dot per pixel is processed separately, which concurs with the previous blurb I read. I still believe that this processing could cause one of those dots to "fire" slightly behind the other two, mimicing the way DLP color wheels produce time differences between the time that each color is rendered. I can see rainbows on an HD3 DLP chip with a 7-segment color wheel spinning at 9600 rpm, which works out to each color of the wheel being "flashed" 1120 times per second. So the time difference between consecutive color wheel segments "firing" is approximately 0.0009 seconds. That's all the time difference any processing would have to introduce to reproduce the effect.
OK, but that's a time difference between the three colors *of each pixel* of nearly a millisecond. That's 40x slower than the time it takes the plasma to draw each line, even assuming that every subpixel in a scanline is fired sequentially, which I think is not true -- I think that many pixels, if not the entire line, are fired simultaneously (have to find some datasheets for PDP driver ICs.). So the three subpixels of each pixel are fired a maximum of about 7 microseconds apart, and probably much closer (depending on whether they fire all red subpixels, then all green, then all blue, or if they fire RGB, RGB, RGB.)

All I can say is that as an engineer, I can't swear that SPC has nothing to do with your problem, but it sure doesn't sound to m e like it could.

I'm not going to doubt what you're seeing, and if it's distracting in normal viewing I guess you'll have to find something else. But if people have to "rapidly scan their eyes", put their nose up to the screen, look at the screen at an odd angle, etc, I'd have to wonder if such problems really mattered. Nearly all display technologies involve something changing at a high rate of speed with the expectation that the viewer's persistance of vision will be unable to perceive that, and I can imagine that there is individual variation.
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post #26 of 140 Old 05-18-2005, 11:14 AM
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I saw the same thing on the 42PWD7UY I had last year, except I would describe the color as closer to green. I was quite surprised the first time I saw it, and I had a tough time ignoring it afterwards. I eventually got used to it though.

I'm also susceptible to the rainbow effect, but I've gotten used to it and don't notice it often on my DLP projector (Optoma H79).
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post #27 of 140 Old 05-18-2005, 12:01 PM - Thread Starter
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I have talked to Panasonic tech support as well as my local service provider today about the issue. As expected, I had a tough time convincing them I was seeing RBE on a plasma, but I'll have a service call soon and will see if there is anything they can do to resolve this. I'm hoping SPC is the cause because if it is, and if it can be disabled in the service menu, that's probably my only hope for keeping the TV.

I'm a very rainbow-sensitive person, for whatever reason. I saw them like crazy on the DLP, and I see them like crazy on this TV. Even though I can see them at will with the rapid-eye-movement technique, I easily see them frequently just watching the TV normally. It's possible I could get used to them, but I'm not willing to pay $4-5K for something I have to get used to.

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post #28 of 140 Old 05-18-2005, 12:42 PM
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Quote:
Originally posted by empire_of_one
The link describes how each RGB dot per pixel is processed separately, which concurs with the previous blurb I read. I still believe that this processing could cause one of those dots to "fire" slightly behind the other two, mimicing the way DLP color wheels produce time differences between the time that each color is rendered. I can see rainbows on an HD3 DLP chip with a 7-segment color wheel spinning at 9600 rpm, which works out to each color of the wheel being "flashed" 1120 times per second. So the time difference between consecutive color wheel segments "firing" is approximately 0.0009 seconds. That's all the time difference any processing would have to introduce to reproduce the effect. Since I've never heard of RBE-type effects on other plasmas, I am only guessing that the SPC that is unique to the Panny could be introducing that delay. It could easily be something else too though.

If anyone's ever seen RBE-like effects like what I've described on other plasmas, I'd definitely like to hear about that. I'm hoping it's a Panny-specific issue so that if it can't be resolved somehow, I can at least consider other plasmas.
I've never seen it but what you describe above is theoretically possible.

Plasma displays use subfields to display grayscale. These fields are time displaced according to what grayscale value is needed. this introduces a time displacement between adjacent pixels. This is what causes the artifact known a 'dynamic false contouring'.

Now if the display is doing this for each individual sub-pixel there could theoretically be a time displacement introduced between adjacent sub-pixels. This would in theory cause temporal color seperation (rainbow effect)

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post #29 of 140 Old 05-18-2005, 02:11 PM
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Quote:
Originally posted by xrox

Plasma displays use subfields to display grayscale. These fields are time displaced according to what grayscale value is needed. this introduces a time displacement between adjacent pixels. This is what causes the artifact known a 'dynamic false contouring'.
Wow, thanks for posting! That's really interesting. Once fired, plasma cells are either on or off, with no modulation of brightness. So to provide grayscale and color, each subpixel is being fired lots of times during the 1/60 second frame time. That does provide the potential for lots of interesting artifacts for people who can see things below the 60 Hz rate, though one presumes that there would have to be some attempt at interframe dynamic adjustment of something (scan pattern or somesuch) to make really visible artifacts.

The US Patent Office database is a rich source of info for those interested in the engineering -- see US Patent 6,738,033 "High resolution and high luminance plasma display panel and drive method for the same" to Matsushita (aka Panasonic) for some background and details. But note this is a 2001 patent, so they may have come up with something better.
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post #30 of 140 Old 05-18-2005, 04:06 PM
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I wonder if this is not just retinal persistence of a high contrast, bright image causing strange visual effects. My brother and I used to have fun with this when we were kids. We'd sit in a dark room and get acclimatized, then set off a flash bulb while staring at a bookcase full of books. The bright flash would leave a persistent image on our retinas that would last 20 seonds or so. You could read the titles on the book covers and the image would move when you moved your head and eyes. Very sppoky. OK, we were wierd kids and this was a rather geeky form of fun. But there is a physiological effect that could be related to the high contrast edges and bright areas of the plasma screen's image when you rapidly dart your eyes over them. I haven't noitced this with my 42PHD6U, but I haven't been looking for it....
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