Slight green tint to picture on TV. Please help if you can...

Discussion in 'Archived Threads 2001-2004' started by James Zos, Feb 10, 2002.

  1. James Zos

    James Zos Supporting Actor

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    I've had my 27-inch Panasonic for at least five years. It's a great TV. But a year or so after I bought it I noticed a very slight greenish tint when watching some movies. On some films it is almost imperceptible, on others it is more pronounced.

    I took my TV in to a local shop when it was still under warranty and I think (I'm not sure) that the repair guy might have fiddled a little with the gray scale.

    But his attitude was, basically, "Hey, this picture looks better than 90 percent of the sets I get in here--what are you complaining about?"

    I got the feeling that he wasn't too interested in really trying to fix my problem. He had to make a minimal amount of effort because it was under warranty, but that's what he did--the minimum.

    The reason I bring this up is because all this time that slight greenish hue has continued to bother me.

    When I described the problem to another shop owner recently he said it was probably the green gun and that he could adjust it. Adjusting the green gun is the same as adjusting the gray scale, from what I understand, but like I said, I'm not sure the first guy adjusted the gray scale, or really did much of anything at all. This new guy also said I should have my picture calibrated every couple of years anyway.

    I have two questions.

    One: What do you think could be causing the greenish tint?

    Two: Is there any point in hauling it in to another shop to see if they could fix it?

    Any suggestions at all will be much appreciated!
     
  2. ThomasL

    ThomasL Supporting Actor

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    James, is the problem only noticeable on dark scenes/areas? That would be indicative of a low end grayscale problem.

    The first thing I'd do is calibrate the set with Avia (or VE or other calibration dvd disc). Once you have Avia, you can do two basic checks to determine if its a grayscale problem (I had a greenish tint grayscale - low end of the scale - problem on my Toshiba 27A40 tv) or perhaps green is being pushed by the color decoder. Go into the color decoder pattern where one can see the relative strengths of each base color in the color decoder. This is normally done as the final basic calibration step in Avia. If green is up near +10 or 15 percent then you have a green push problem. The easiest way to fix this is to just lower the overall color saturation a few notches until the over emphasis of green no longer bothers you. On my Toshiba, I also have a slight green push (very slight) but one of the things I noticed is, even after fixing the grayscale, some cable programs still look a tad green and I believe this is due to the source as well as to the fact my eyes were trained for years on a television that suffered from bad red push (many do).

    If you find that the color decoder isn't suffering from green push, then the next thing to do is to go into the grayscale patterns. I like the windowed IRE patterns as well as the vertical ramp pattern. Look to see if your eyes see the green tint here. As most people here will tell you, it's hard to set grayscale eyeballing it, but if the tint is bad enough, you should be able to see it. If indeed some part/range of the grayscale looks green tinted, then it's a grayscale problem. If so, there are two solutions. One is to hire a ISF calibrationist to set it to D6500K using a color analyzer. The other is to get a hold of the service manual for your tv, and figure out which variables/parameters control the grayscale and change them yourself by eyeballing it using the above mentioned patterns. If you know how to use a colorimeter or a color analyzer, then that would be a bonus. I had to use the eyeball method. While, I know it's not D6500K, it's a lot better that what it was out of the box.

    hope this helps,

    --tom
     
  3. James Zos

    James Zos Supporting Actor

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    Tom--thank you so much for your detailed and very well thought out response! I only hope I can take advantage of it, as I know very little about calibrating a TV.

    I don't yet own AVIA but am planning on ordering Sound and Visions latest test disc, because it has 6.1 test tones on it. However I have heard that this disc is a little skimpy on picture calibration--do you think it would suffice for the calibrations you have listed here?

    Though I use a sound meter to balance my speakers, in the past I have always used my own eyes to set the picture. I go for what I feel looks as close to "real life" as possible. This has worked fine for me--except for that damned green tint! I mention this because you suggested I lower the overall color saturation to see if that lessons the problem--I tend to have color saturation toned down to begin with because I dislike bleeding or unnaturally glowing colors. Even so, the green is still evident...

    I would have to say that the greenish hue is noticable in BOTH dark and light areas of the screen, because I particularly tend to notice it in flesh tones: there will be just a hint of green in otherwise natural-looking complexions.

    If I can use AVIA to determine that it is a grayscale problem--how do I go about getting my hands on a service manual? I assume that would then mean opening the TV up? I've read that it can be dangerous for the amature to do so. But it stands I only have access to the basic, consumer level settings such as color and hue, etc...

    My last question is the most basic one: What does "ISF" stand for? And how likely is it that the guy in the local shop would be one?

    Thanks again for your help!
     
  4. James Zos

    James Zos Supporting Actor

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    bump.
     
  5. ThomasL

    ThomasL Supporting Actor

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    James,

    I have no experience with the Sound and Vision calibration dvd so I can't help you there.

    The service manual for your tv would be something you'd have to order from the manufacturer. Most likely adjustments to grayscale would be done with the service menu. But I must warn you that such tinkering in the service menu can put your tv into a hopeless state if you don't know what you're doing. I'm assuming that the guy at the local repair shop must have went into this menu when he tinkered with the graycale. Basically, you'd want to do the same thing but have test patterns up there so you can see what you're doing. This is where Avia or another calibration disc will come in handy - at least to determine if indeed that is where the problem lies.

    ISF, I believe, stands for Imaging Science Foundation but someone can correct me if I'm wrong. No, your local repair person is most likely not an ISF calibrationist. I'll let others who have much more experience in these matters discuss it further.

    cheers,

    --tom
     
  6. James Zos

    James Zos Supporting Actor

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    Thanks Thomas!
     

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