I see rainbow-like effect on some LCD TVs - AVS Forum
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post #1 of 8 Old 06-06-2008, 06:13 AM - Thread Starter
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Hello everyone,

I don't know if it has been discussed on this board earlier, but I seem to be able to see this rainbow-like effect on LCD TVs too.

I recently bought a Sony KDL-40W4000 and I can easily see some greenish flashes in high contrast scenes (still images too) when I move my eyes from side to side.

This effect seems to be most noticeable when the backlight of the TV is set to minimum. If I increase the backlight to almost maximum I cannot see it anymore.

There are some other people in AVForums who see the effect also and currently there is at least one explanation to this:

Quote:
Originally Posted by steverobertsbbc View Post

The rainbowing is the backlight dimmer - it uses pulse width modulation to control the amount of light and the flicker beats with the panel refresh rate. The lower the light, the less time the tube is illuminated for and the more obvious the rainbowing. At max backlight, it's on constantly and there is consequently no rainbow effect.

If you have a PS3, put it in the mode where it asks you if you want to turn off the system, which gives you bright white graphics on a black screen. Put the backlight on minimum and just flick your eyes around the screen, you'll see predominantly green flashes. Turn the backlight up and the effect reduces until it disappears at max setting.

Source

So far it has been reported to occur with Sony Bravia W3000/W4000 and X3000/X3500 models.

Has anyone else in this forum seen these flashes? Can anyone provide a complete explanation to this effect and why don't some people see it at all?
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post #2 of 8 Old 06-06-2008, 07:14 AM
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I see rainbows on plasmas (yellow), RP-CRTS (red), and DLP (all colors). I've never seen them on a LCD but that doesnt mean they aren't there. I'm currently running a samsung 550 and have had the blacklight from 3-6 and haven't noticed anything, so I'll count my blessings.
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post #3 of 8 Old 06-07-2008, 01:23 PM - Thread Starter
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I recorded some video of the "rainbow effect" today and was surprised that even my camera showed the same effect.

See the screenshots:

Backlight set to 0:


Backlight set to 9:


These images were extracted from a video file which was recorded in VGA 30fps.
The picture on TV was stationary and I only moved the camera quickly from top to bottom.

Can anyone explain the green trail that is shown in the first screenshot?
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post #4 of 8 Old 06-07-2008, 01:27 PM
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yeh I see this effect more noticeably on plasmas. on LCD it isn't as noticeable, but it is still there if I move my head side to side quickly. for most people, they don't see them at all. but a few of us who have sensitive eyes will be able to pick out the green trails.
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post #5 of 8 Old 06-07-2008, 01:54 PM
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Quote:
Originally Posted by Yume View Post

I recorded some video of the "rainbow effect" today and was surprised that even my camera showed the same effect.

See the screenshots:

Backlight set to 0:


Backlight set to 9:


These images were extracted from a video file which was recorded in VGA 30fps.
The picture on TV was stationary and I only moved the camera quickly from top to bottom.

Can anyone explain the green trail that is shown in the first screenshot?

I think I know what you are trying to say, but if the picture on the TV is stationary then what you captured here is an effect of the camera not the TV.
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post #6 of 8 Old 06-07-2008, 03:30 PM - Thread Starter
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Quote:
Originally Posted by primetimeguy View Post

I think I know what you are trying to say, but if the picture on the TV is stationary then what you captured here is an effect of the camera not the TV.

Well if it is the effect of the camera, why isn't is showing on every backlight value? Basically my camera is seeing it just like I am but I am seeing it a lot worse.

Anyway, this time I took new screenshots when camera was stationary and video was playing:







Screenshots are from Sin City, an awesome movie but one of the worst case scenarios to spot this effect.
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post #7 of 8 Old 06-07-2008, 03:46 PM
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I have seen this effect too on a 46W3000. It appears that the picture is breaking up and displaying a flash of green before the whole image "comes together". For a while I thought I was seeing things.
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post #8 of 8 Old 01-04-2009, 02:05 AM
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We have a Philips 9703 model and we are the same "green flash" effect, ecpecially on dark scnes with high contrast points. Colors are green and sometimes red.

We haven't had the same problem with other philips models we have owned. That is why we thought it was eather the _white color gamma gamut_ feature that enhances the colors.

We have no option to control the backlight but putting contrast very high seems to reduse the effect. Bad thing is that the screen is bright enough so it doesn't feel right to do so and i wonder if it also shortens the life of the tv panel.

If I and my huspand have both the "rainbow seeing" gene and we have children someday, they can only look 3D movies !

Happy new year!
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