Lens stripping questions

Discussion in 'Archived Threads 2001-2004' started by Maximil, Aug 16, 2001.

  1. Maximil

    Maximil Agent

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    I just tried this on my 55HX70 and am unsure if I'm doing this correctly. Using standard width electric tape, I placed a strip (covered the sticky side to protect the lens) over the the inside edge of the red and blue lenses.
    Is there an indicator, say using Avia, as to how far in to place the tape? A standard for a 55" TV?
    How does this work? I was expecting to see the red and blue completely cut off by the tape on either end of the screen, but it only lowers the output, like it is supposed to. Interesting to me.
     
  2. Jeff D.

    Jeff D. Supporting Actor

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    Technically, what you are doing when striping the lenses is balancing the colour temperature across the screen area.
    Inside your TV, the three CRTs are arranged from left to right as follows:
    Red - Green - Blue
    The Red CRT is angled to the right and the Blue CRT to the left.
    What you see on the screen is a reddish tinge on the right side of the screen and a bluish tinge on the left (though this is sometimes not as noticeable).
    Measurements with a colour analyzer confirm that there are two factors at work here:
    On the right side, the image is tinted red because a)the Red CRT is "aimed" at the right side and thus there is an excessive amount of red on that side of the screen and b)the Blue CRT is "aimed" away from the right side and thus there is a drop in blue's output on this side of the screen - which only serves to make the red more apparent. The same, but opposite (in terms of the colours) problem occurs on the left side of the screen, with a resulting blue tinge.
    Remember that grayscale is not just a number (6500K is the one we all think of). This number only refers to a specific colour temperature. However, as Guy Kuo has so effectively pointed out, a colour temperature of 6500K can be achieved in many (inaccurate) ways. A qualified tech who adjusts your grayscale will adjust for the proper balance of the three colours to achieve the colour temperature of 6500K.
    Keeping that in mind, for best results, lens striping is really just adjusting the colour temperature (and aiming for the proper colour balance) across the screen area.
    As this is technically a grayscale adjustment, proper measuring equipment is required for truly accurate results. A gray field is used to do these measurements - essentially the same as the grayscale test patterns, only the gray covers the entire screen. Measurements with a colour analyzer are then taken at various points across the screen area.
    Of course, this can also be attempted by eye. Use one of these gray fields to check your results.
    Be wary of one thing: as I mentioned earlier, there are two factors at work on each side. Don't keep covering more and more of the red until it completely disappears - you'll soon find the right side will turn green. Why? Remember - it is not only an excess of red but also a lack of blue causing this problem. Sucking away too much red means that there is now too much green. It is all a delicate balancing act.
    Of course, the first question to pop into your head is - how can we boost the blue output? Well, technically we can't. But I have been experimenting with a workaround - boost blue by cutting green. Yes, I have experimented and found that, if one wants a linear grayscale across the entire screen area - with proper colour balance as well - then striping of the Green CRT is necessary as well. Of course, this makes the operation a little more involved, but the results have been well worth it.
    Also note that some sets do not require as much lens striping as others. This has been widely reported from techs such as Michael Chen. Obviously there are various factors at work. Some manufacturers even apply their own striping at the factory. I've seen this on Toshiba and Pioneer sets.
    Finally - to your last question as to how this works, it all has to do with the optics. I'm no expert on optic theory so I'll say no more. All I do know is you can cover up various parts of your lenses and the whole image will still be there. [​IMG]
    Good luck in your efforts.
    ------------------
    "They're coming to get you Barbara..."
     
  3. Maximil

    Maximil Agent

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    Thank you for the detailed explanation, all my questions are answered.
    I think I'm seeing the greenish effect on both sides now, so I think I will move the stips to the side just a little more.
    Thanks again (:
     

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