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Numpty Seeks help with screen height calculation

Discussion in 'Projectors, Screens & Video Processors' started by catesby, Mar 11, 2005.

  1. catesby

    catesby
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    Hello there

    Optoma tell me that the H57 has a vertical offset that is 54 percent of the image height. Can anyone tell me what this means to help me work out how high I should put my screen?

    Thanks
     
  2. KraGorn

    KraGorn
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    It means that if the lens is level with, say, the top edge then the lens shift can move the image down so it's centred on the screen. That said, you really don't want to use any more shift than you really need because often it introduces slight focussing problems due to minor imperfections in the lens system.
     
  3. Piers

    Piers
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    I am treading on dangerous territory being principally a plasma man (albeit also having an H57!). My understanding is that the H57 doesn't have any optical lens shift but has an in-built 54% correction. If I have got this right it means that you don't need the projector at exactly the same height as the centre (vertically) of the screen. Mounted on the ceiling, 54% of the image height down from the ceiling will require no vertical keystone correction. Ditto 54% up from the floor if mounted table-top.

    No doubt if I have got this wrong someone will put us both right - suffice to say I am blown away by the PQ of my H57 and the fact that it is hush quiet.
     
  4. KraGorn

    KraGorn
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    :oops:

    I think you're right Piers, I mis-read vertical offset for lens shift.
     
  5. Joe Fernand

    Joe Fernand
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    Catesby

    The Offset enables you to set the projector low or high in relation to the Top or Bottom edge of your screen without having to invoke any digital jiggery pokery (Keystone correction) to ensure you have an image that's not wider at the top than the bottom.

    The amount of offset should not dictate where you put your screen - your eye level dictates that; the offset dictates where you place the projector once you have the screen set.

    Measure the distance from floor to your eye line when your sat in your favourite position and now use that as your guide height - some folk like the image to be 50/50 above/below eye their line others prefer it more like 70/30 above/below as they prefer to look up a little and it 'looks' more symmetrical in your room.

    Once you set your eye level and decided on a screen size you can then look at ceiling, wall or coffee table mounting the projector and that's when the offset calculations are required.

    Best regards

    Joe
     

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