Geometry issues: Is flat-tube worse than curved tube?

Discussion in 'Displays' started by Rudolph V, Dec 25, 2003.

  1. Rudolph V

    Rudolph V Extra

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    I recently purchased a new JVC AV-27F704 flat-tube CRT TV (27") to replace my aging 19" Sharp curved-tube TV. Even though the JVC has a much improved picture quality, I do notice that it's flat tube has quite a bit more geometry distortion than the older curved-tube Sharp.

    Is geometry distortion a general problem with flat-tube CRTs (of all brands) compared to the older curved-tube design, or do I just have a bad unit?
     
  2. Jeremy Scott

    Jeremy Scott Second Unit

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    describe your problems here......be specific.
     
  3. Rudolph V

    Rudolph V Extra

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    I'm referring to geometry distortion, i.e., If you display a uniform grid on the CRT there will be areas where the "grid squares" will be distorted in either the vertical of horizontal direction (sometimes both).

    This causes constant speed horizontal or vertical panning shots to have "weird" roll-off (lensing) distortion.

    See here for an example: geometry distortion.

    Note that I have "exaggerated" the extent of the distortion in this example. It is much less evident on my screen. A static shot will not reveal it for any normal TV/movie image. Only when the image pans from left to right or up and down does it become noticeable. Another good place to look for such distortion (at least the vertical kind) is during the 'end credits' of a movie, i.e. vertical scrolling.
     
  4. JohnSmith

    JohnSmith Supporting Actor

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    Depends what aspect mode you've got the set in. From that sample grid it looks like a widescreen "squash" so 4:3 material looks acceptable full-screen on a widescreen set.

    Or do you mean this effect is seen in all aspect modes? Have you got Avia DVD? can you take a snapshot of the exact problem?
     
  5. Jeff W.

    Jeff W. Stunt Coordinator

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    Flat screens do tend to have geometry issues at the edges. The alternative is good ol' round picture tubes that distort *all over*. You really have to pick your poision.

    I.e. a "flat-screen" tube will be very flat in the middle, but then have a little bend about 2" from the edges. While a round tube will just have bug-eyed bubble distortion throughout.

    Of course price is an issue. I paid $600 for my Sony WEGA flat-screen 27". It has a little bend at the edges, most notable on "ticker-tape" stock market scrolls. You can currently get a 27" "flat screen" for as little as $350, but will the quality be as good? Unlikely...
     

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