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Setting the contrast on a CRT RP set question...

Discussion in 'Displays' started by Vader, Jul 19, 2007.

  1. Vader

    Vader Well-Known Member

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    Derek
    Hi all,

    I have a quick question for the calibrationists here. According to the tutorial on DVE, the contrast should be set just below where blooming starts to occur. Problem is, I really cannot tell exactly where that is. I saw on another thread that LCD sets don't have blooming, and instead use the "Grey Ramps" to set contrast. This I can see quite easily, but is it a valid way to set contrast on a CRT? Right now, I have the brightness calibrated using the "DVE Pluge W/ Grey Scale", and the contrast is just were it looks good (to my eyes), and is well below the danger level (about 25-30% in my case). Any other suggestions? Thanx!
     
  2. JeremyErwin

    JeremyErwin Well-Known Member

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  3. Vader

    Vader Well-Known Member

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    Thanks, Jeremy!

    Good stuff. I negelcted to mention that my display is analog, not digital (Mitsubishi 65511). What I am hoping for is a definative "yes, the using the grey ramp pattern will give equivelent results on an analog CRT" or "no, the grey ramp pattern is unsuitable for analog displays as the results will be inaccurate."
     
  4. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    Michael Chen
    Greetings

    The contrast patterns with needle pulses and gray boxes where we either look for blooming on the edges or bending lines are not designed to help you set optimal contrast on a CRT set.

    Their purpose is to help you identify the maximum point in the contrast control not to exceed. This is the proverbial red line for the contrast control in the TV.

    This is where you should not be setting contrast ... but it does not tell you where you should set it.

    If the red line in my car is at 6000 rpm ... I do not drive my car at 5999 rpm. Same goes here.

    Recommended contrast on CRTs is determined with a light meter ... typically. So on a set like yours ... a 100% white windowbox pattern should give a reading of roughly 20 ft-l of light output. However ... the lenticular screen on the TV usually screws up the light meter's absolute readings so you shoot for a reading of around 7-8 ft-L ... there is a 2.5 to 3X rule that needs to be applied.

    So if you got 8 ... it's really 8x3=24 ft-L ... and you are there. Because of this ... if you set it to 20 FT-L ...based on a meter ... you are actually doing 50-60 ft-L and that is bad bad for the TV.

    Without a meter ... use the eyefatigue method. Look at the same 100% windowbox pattern and adjust until the box does not bother your eyes to look at.

    You still need to determine where that red line is first though.

    REgards
     
  5. Vader

    Vader Well-Known Member

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    Michael,

    Am I understanding you correctly in that I can use the grey ramp pattern to determine the red line on my RP CRT, but I use the eyefatigue method to find what is most comfortable to me (and that as long as it is significantly below the redline I am OK)?
     

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