Rainbow effect on CRT TV?

Discussion in 'Displays' started by Randy Flowers, Oct 8, 2004.

  1. Randy Flowers

    Randy Flowers Auditioning

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    I have heard of the rainbow effect on HT projectors, but never on a television set.

    However, while watching LOTR 3 on my 27" Toshiba, during one of the major battle scenes, the picture was inundated with reds and blues and greens, as if the TV couldn't "keep up" with what was happening. It was so bad it was hard on the eyes to keep watching.

    The TV settings have been set using Avia.

    Can you get the RBE from a CRT, or is it some problem with my set? Thanks.
     
  2. John S

    John S Producer

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    Direct view CRT???? Interesting.. I have to ask, please don't be mad... Your not using regular AV V/L/R cables for your Component Video connection are you? I have seen this cause this somewhat during heavy action scenes with lots and lots of motion going on is all.

    Knowing this, I guess, it could be a cable issue in general.
     
  3. Randy Flowers

    Randy Flowers Auditioning

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    Thanks for the reply. It is indeed a direct view TV.

    I am using true component cables, though I don't remember the brand name. I got them at BB.
     
  4. ChrisWiggles

    ChrisWiggles Producer

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    I'm very fuzzy about what it is in the picture that you are describing,


    This doesn't compute with anything that I have seen or recognize. Could you describe more specifically what you mean? Does this look like compression artifacts? Is it actually showing splotches of color where there should be none? Or what?

    If you understand what rainbow effect is on single chip projection displays cause by a color wheel, you realize that CRTs won't have the same problem. Where they may have a problem is with flicker, and differences in phosphor decays, which may lead some viewers, on some sets, to see flicker problems, or the residual effects of the different decayse of phosphor (green being the slowest). On my CRT projector, at low refresh rates, you can see flicker clearly. Running up to say 60hz eliminates most visible flicker (unless you look away from the screen, your peripheral vision can sense flicker/motion better), but if you dart your eyes around as if you were looking for rainbows on a DLP, you can see some coloration even in a B&W picture, ever so slightly, usually a puke-like greenish color which relates to the slower green phosphor decay. AT even higher refresh rates this is all but completely eliminated. This does not sound like what it is you are seeing, but as for effects similar to rainbows on a CRT, this is something that may exist.

    Many direct view sets especially, designed for interlaced video, have EXTREMELY slow green decays to minimze flicker visibility, and this causes very visible green phosphor trails, which are best seen in dark scenes with very bright moving objects. You can see the green decaying much slower, as greenish trails behing the moving object on a dark background. This depends on the nature of the phosphor decay time, as to what effects might be visible, along with the refresh rate.
     
  5. Randy Flowers

    Randy Flowers Auditioning

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    Thank you for the educated response. What I saw in that particular scene was very similar to what I have witnessed on DLP projectors, though I didn't have to dart my eyes to see the problem. The scene included very dark horses and very dark men, running / fighting with a very bright sky & horizon. For instance, when a horse was running, it's black leg was followed by a green streak (or a green "leg") or a red streak (or a red "leg".) Because there was so much movement, it was a real "in your face" burst of colors. As soon as the scene slowed, the reds and greens went away.

    A silly question, I know. However, I am willing to appear as an idiot in order to settle my curiosity.

    Thanks for the replies.
     
  6. ChrisWiggles

    ChrisWiggles Producer

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    Hmm, the green streaks might be something like the green phosphor trails I described, but these are usually best seen on very black backgrounds, and vary from display to display. Also, that you mention red, that would not really happen in this situation, so I'm betting it's probably a source problem, like MPEG artifacting due to perhaps poor decoding, etc, maybe a dirty disc, maybe a poor player, I dunno. But I would look more towards source before the TV.
     
  7. Steve...O

    Steve...O Producer

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    I have been having a similar issue with my 60 inch Phillips. Green flashes appear from time to time. I called Phillips and they didn't have an answer for me so I called a local authorized dealer and they're supposed to come out and look. However I'm not sure if that will do any good since I can't "make" the flashes happen to show the tech. They do seem to appear more frequently on black backgrounds. (They appear on multiple inputs so I don't believe it is a source issue).

    Can anything be done about this or am I stuck with these green flashes?

    Thanks,

    Steve
     
  8. Max Leung

    Max Leung Producer

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    When I see them on my Toshiba TW40X81, they show up as yellowish streaks. I've also seen it on a Pioneer 5xx 50" widescreen RPTV as well. In fact, it was extremely prominent on the pioneer set, because it was set for a very high contrast, roughly 40 ft-Lamberts (about twice as bright as a TV set set to movie-theater light levels). This is with a Panasonic RP91 DVD player set to progressive mode.

    The Two Towers Helm's Deep battle scenes at night illustrate this effect very nicely. It is almost as distracting to me as DLP rainbows if the contrast is set high enough. [​IMG]
     
  9. DaveNel

    DaveNel Second Unit

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    Hello

    Do you have speakers to close to the TV, Magnets in the speakers may be causing your problem.
     
  10. Randy Flowers

    Randy Flowers Auditioning

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    I do, though they are 8" away with 2 layers of 3/4" plywood between (entertainment center). This coupled with the "magnetically shielded" speakers, I am doubtful (yet not convinced) that it is not the speakers.

    Thanks.
     
  11. Dave Poehlman

    Dave Poehlman Producer

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    How about a subwoofer? Those sound like heavy bass scenes you're describing. Perhaps that's too close?

    Also, have you tried a different DVD player? Perhaps yours has got a problem with the output.
     

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