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CRT and LCD cropping a big problem...

Discussion in 'LCD & LED LCD TVs' started by spergabite, Aug 11, 2004.

  1. spergabite

    spergabite
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    I have been contemplating buying a samsung 32" lcd tv recently -I visited currys a few times and checked the pictures etc. Today I noticed that some of the lcd screens including the samsung cropped the left and right edges off the screen. I assumed that this was because it was 15:9. I investigated this on the forum and found that it was a widely reported problem. So I returned to currys to have another look. What i did find out is that the crt screens suffered from the exact same problem!! - Can anyone explain this. ? Im confused

    regards
     
  2. LV426

    LV426
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    Separate issues.

    1: 15x9 flat panels have to do something to fit the picture to the shape. Some may overscan horizontally by a bit too much; others may underscan vertically a tad. And others may deform the image to fit.

    2: ALL TVs overscan in both directions. It's a throwback to

    a) CRTs (which still exist, and still exhibit the same arefact) where edge geometry isn't 100% perfect. Overscanning hides what might otherwise be a bowed or tilted edge. Having said that, 16x9 TV makers haven't woken up to the idea that pillarboxed 4x3 images, or letterboxed 22x9 ones, both demonstrate their shortcomings - they are still making them with geometry tolerances that are too wide.

    b) Early TV studio equipment which wasn't guaranteed to produce edges to images that were consistently in the right places.

    So all TV signals have a "safe" area within the overall shape, inside which, anything important of the picture is; and outside which there's still a picture, but containing nothing important. In theory.

    In practice, films which use the full width of their frame often do demonstrate this cropping. The start titles of ALIEN are an example.

    Also, in practice, the same is true of cinemas. All (or most at least) have their projectors set up to throw an image slightly larger than the area bounded by the screen masking.
     
  3. MAW

    MAW
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    Check out the latest Hitachi news, we are talking 5% overscan all round! But as Nigel says, a small amount is actually useful. Check out something like MTV on a plasma or LCD, unless you dial in a bit of overscan, the top of the picture demonstrates clearly what he refers to. With a CRT this built in overscan prevents you noticing.
     
  4. calscot

    calscot
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    DVD players also overscan the images sent to the tv. A calibration dvd like Avia will show you how much is overscanned.
     

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