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Vertical Offset Problems and Questions

Discussion in 'Projectors, Screens & Video Processors' started by catesby, Mar 3, 2005.

  1. catesby

    catesby
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    Hello all

    I was thinking of buying a Screenplay 4805 but have hit the vertical offset problems that others on this site seem to have faced i.e. to get the screen at the viewing height I want and the size I want the projector has to be 85cm from the ceiling – which is just too much.

    Three sets of questions follow:
    1. Why is it that it's not recommended to mount the projector closer to the ceiling and use the keystone function to correct? Does this damage the image quality or what?
    2. If I need to now consider a proj with Lens Shift, which is the best for around the same money as the 4805?
    3. Another idea I had was to mount the thing in/on a small table with castors and wheel it in and out of position when needed. Has anyone done this? How susceptible are projectors to damage if they get knocked while turned on? How much of a pain is this? What about all those trailing wires?

    All advice/comments greatly appreciated.
     
  2. KraGorn

    KraGorn
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    Keystone adjustment is bad for image quality because it's done by the projector's scaler and involves massaging the pixel information to correct the geometry. Any form of scaling will tend to degrade the image, though unless you're projecting at the same resolution as the DVD itself (ie. 720x480 or 7620x576) then you'll always incur a scaling operation somewhere. That said, the processing needed to correct keystone tends to hurt the image even more.

    As you seem to know, your best bet is to get a projector capable of using Lens Shift, which is an optical operation and therefore doesn't degrade the image, except if taken to extremes.

    I've no idea what price the 4805 is so can't really advise, there are several popular projectors at various prices the do vertical shift and one or two do horizontal as well.

    You can buy projector stands on casters, with wheel-locks. The main trouble is having to re-adjust the projectr for location and focus each time. It's safe to say a projector wuldn't take too kindly to being knocked on the floor, not sure how much of a 'knock' you're taking into account.
     
  3. catesby

    catesby
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    Thanks Kragorn. Would appreciate a recommendation from you on a proj with lens shift. The 4805 seems to cost about £1000.

    Thanks
     
  4. KraGorn

    KraGorn
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    The Hitachi PJ-TX100 is more or less £1000 and does, a bit higher (£1100 or so) the Z3 vertical shift, as does the AE700 for a little more again (c. £1250), all are popular machines.

    There's a currently active thread discussing the TX100 and AE700 you may find useful.

    There are probably more, I'm not too well up on the current £1000 market.
     
  5. guido

    guido
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    Z3 (LCD) has the biggest lens shift I know about and is only just outside your budget (£139 more than SP4805).... maybe you can save on another item... e.g. the screen?

    The H30A has some sort of digital lens shift (?) Its descibed in a review here: http://www.projectorcentral.com/optoma_h31.htm (H31 is USA is same as H30A here).

    You can get some nice small (coffee) tables with a rising top, the projector sitting underneath. When PJ not in use just push top down. Suitable only if such a table is not going to be in the way.
     
  6. catesby

    catesby
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    Guido

    You mention some nice coffee tables with rising tops. This might work for me. Are there any good sites on the web where I can see some of these?

    Thanks
     
  7. guido

    guido
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    This is the place I had seen them, give you the idea... but there are plenty of others:
    http://www.kenthomecinema.co.uk/html/longbow_projector_cabinets.html

    Guido
     

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