Picture Centering Problem

Discussion in 'Archived Threads 2001-2004' started by Dave H, Dec 23, 2001.

  1. Dave H

    Dave H Producer

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    Since having my overscan corrected, I put in the centering grid in Avia - where you can view different aspect ratios, etc. and their positions on the screen and have noticed that the picture's centering seems to be off. The left side of the picture is shifted so that I can't see the full edges of the right AND left portions of the picture. Is this something easily fixed, or does overscan have to be corrected again.

    Another example that might clarify this. I put in the widescreen side of "The Never Ending Story". As the movie starts, the title is spread across the entire widescreen (2:35). The "T" in the word "The" is slightly cut off because of the problem I'm stating.

    Now, the ISF guy told me my TV was harder to adjust the overscan for because of some internal flaws of the set and that the factory problem overscanned the way they did to compensate for this. But, is the overscan that's causing the slight cut off of the right picture, or is it something else?

    The ISF guy is coming back to take a look at this for me - just want to know what I should be aware of. Thanks.
     
  2. Dave H

    Dave H Producer

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    Anyone? I know I'm not the first person to ever have this problem. What are the remedies?
     
  3. Guy Kuo

    Guy Kuo Supporting Actor

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    Dave, it may well be a complete redo of geometry and convergence to fix everything to your satisfaction. Basically, to check what is going on display the AVIA overscan pattern and verify by measuring on the screen that the pattern is indeed exactly centered on the screen. Unlike the VE overscan pattern, the one in AVIA actually centered in the DVD frame. Be sure to set the display aspect ratio such that the pattern fills the entire screen without cropping. In other words, the height of the pattern should fit the height of the screen and the width of the pattern should fit the width of the screen.

    Once true centering is verified, you can use each edge of the pattern to read the amount of overscan. The amount should be equal on all four edges. 3% overscan should be considered good on a consumer display. Up to 5% is acceptable. Less than 2% and one risks showing the noise which often appears at the edges of the video frame.

    Give your description of your sets calibration, it is quite probably that some distortions near one edge of the image on your set forced the calibrator to intentionally leave things slightly off center to hide the problem. That would pull the centering to the side and make measured overscan unequal side to side. If this is the case, then you can either live with things being off center but with less overall overscan or have things redone with true centering but greater overscan to hide the edge problem. Pick your poison (and how much it costs to drink it)
     

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