How to Adjust Image for Projector Tilt?

Discussion in 'Displays' started by Bill_Br, Oct 5, 2006.

  1. Bill_Br

    Bill_Br Agent

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    Hello,

    We have a Toshiba TDP-T91 projector that we'd like to use in a home-theater setup. If we set up the projector directly behind where we'd be sitting and had it aiming at right angles at a screen set up at eye level, well, naturally our fat heads would get in the way.

    Therefore, we're thinking of using a ceiling mount. Being a newbie to home theater arrangements, my question is pretty basic: Is there a lens attachment one can purchase to compensate for the picture distortion that occurs when the projector is projecting at an angle, as it would be from a ceiling mount? If yes, is there much loss of picture quality?

    How do other folks deal with this issue? Have the screen higher up? Buy a projector with a built in adjustment feature?

    The projector can be configured for rear projection, but the amount of space needed behind the screen probably would be prohibitive, although we might be able to do it if there are no other options.

    Thanks for your help!

    Bill
     
  2. Jim Mcc

    Jim Mcc Producer

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    Every projector has a feature called keystone correction. This corrects the image digitally to regain the square shape. Video purists will tell you never to use keystone because it affects image quality. But with most projectors you'll never see any difference in image quality. I know I don't.
     
  3. Bill_Br

    Bill_Br Agent

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    Thanks, Jim. After starting this thread I did a little more research and discovered that, yes, the projector does have that feature. Strangely, the manual that came with the unit doesn't mention it but another user manual that I found online for the exact same unit does explain how it works.

    Bill
     
  4. Leo Kerr

    Leo Kerr Screenwriter

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    Also, many projectors don't project like you're familiar with slide projectors.

    Instead, many are "off axis," where, if the projector is sitting on a table, the bottom of the image stays in-line with the projector.

    Optical keystone correction is generally okay; digital keystone correction is, very often, pretty ragged, and will also often act as a major blur filter.

    Leo
     
  5. ChrisWiggles

    ChrisWiggles Producer

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    Not all projectors have the same keystone capabilities.

    Many have offsets which can be adjustable, which is a physical adjustment and very useful. This should be described in the projector's specifications.

    As for non-physical keystone correction on a digital display, that is HORRIBLY destructive to the image, and should never be used except for non-critical tasks (powerpoint presentations etc).

    Electronic keystone on a CRT display is a bit different, and not degrading that electronic keystoning on a digital display is, because a diigital has a fixed pixel grid while a CRT does not have a fixed pixel array.
     

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