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Overscan? What should it be?

Discussion in 'Archived Threads 2001-2004' started by MikeyWeitz, Apr 4, 2002.

  1. MikeyWeitz

    MikeyWeitz Supporting Actor

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    What is the best setting for overscan? Right now I have the 5 half way cut off on the top, bottom and both sides. Is this correct or should it be closer to the 10? I am using the VE test pattern. Thanx.
     
  2. RyanDinan

    RyanDinan Stunt Coordinator

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    Hi,
    If using a direct-view CRT monitor, the less the better. 5% overscan is pretty good. Some people like it closer to 2-3%, that way they're seeing almost all the image.
    If you have a RPTV with some sort of auto-convergence feature (Flash Focus, Magic Focus, etc.), then there needs to be a minimal amount of overscan to make that work, as there are sensors inside the bezel that read the light from the CRT's. If overscan is reduced too much, the light won't hit them, and they may return errors. For RPTV's, I would stick close to 5% as a minimum to ensure that you don't lose the funtionality of the auto-convergence feature.
    However, I don't use my auto-convergence (I manually converge my set), so I could go as low as 0% overscan if I wanted.
    For 4x3 material Im at 5%. For 16x9 DVD/HD material, Im at 1.8% according to AVIA's pixel cropping pattern [​IMG]
    Definately keep overscan under 10% - That's overkill. But it's not uncommon for consumer sets to have 15-20% overscan out of the box.
    In fact, during video production (my job), we design all graphics/text to fit within a 20% "safe" zone, which ensures that those sets won't crop off important information. Terrible....
    And if you read the recent thread here about overscan, the more you reduce it, the more resolution you're going to see in the same area - So you'll get a sharper, higher-resolution image as well.
    -Ryan Dinan
     
  3. DenR

    DenR Auditioning

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    Fine reply Ryan. But with respect to CRT (direct-view and RPTVs), let's remember the main reason many manufacturers set high overscan at the factory: lousy high-voltage power supply regulation.

    By minimizing overscan, you are increasing the amount of information getting to the viewable area. That will increase the beam current and thus the dynamic demands on the HV supply; most sets won't come through smelling too sweet. The main symptom you notice is "bounce", where the size of the picture is constantly varying based on brightness level. Easy to notice by putting on ESPN News with the stats banner along the bottom; the text will grow and shrink, move around and otherwise drive you nuts. The only solution is to turn down the Contrast. The set makers know you are going to run the Contrast at too-high levels (hell, they ship it that way), so high overscan helps hide the problem.
     
  4. Ken Garrison

    Ken Garrison Supporting Actor

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    I got a POS Magnavox 1989 25 inch TV that is very bad at bouncing, overscanning, and any straight lines at the top and bottom are curved and distorted. This drive me nuts. I WANT A NEW TV!!! Anyway, in the mean time, I'd like to get a couple of variable resistors and put one on the vertical coil and one on the horizontal coil and hope that can force it to shrink the picture a little so very little of the image is cut up. Probably no way to make those lines straight.
     

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