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Do LCD projectors really have dead pixels and if so, how do you check?

Discussion in 'Projectors, Screens & Video Processors' started by calvinhobbes, Sep 23, 2004.

  1. calvinhobbes

    calvinhobbes
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    Hi All

    I'm thinking of getting the new AE700 Panny, but from a place that doesn't do dead pixel checks - is this really a concern for LCD projectors?

    Also, sounds stupid I know, but how do you do a dead pixel check at home - is it literally looking for places where the pixel on the wall / screen doesn't move?

    Cheers
     
  2. LV426

    LV426
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    They can have them from new. But they are reasonably rare. And they can develop them over time, but this is much rarer. Generally, if its free from such defect after about a week, it will stay that way.

    Bad pixels on an LCD projector can be:

    - darker than they should be or totally dark - in which case it will show as a darker, coloured spot on a completely white image (eg if a green pixel is dark, there will be a magenta tint to a spot on white). Failed/dark pixels are VERY VERY rare and virtually invisible in normal use so I'd ignore them unless you're paranoid about such things.

    - lighter than they should be or fully illuminated (transparent) - in which case it will appear as a bright pinprick on a totally black image. A failed/bright green pixel will produce a bright green spot. So, the test for this is to project a plain black image and look for bright pinpricks.

    A failed pixel is (unsurprisingly) sharply defined and exactly the same size and shape as all the other good pixels. In will be exactly or almost exactly square. If you get close enough to the screen, you will probably be able to see the "mesh" that is the pixel grid structure - and a failed on will just exactly fill one of the "holes" in the "mesh".
     
  3. mhouston

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    Nice explanation nigel...How noticable would any of the above be on a machine like the AE700...would the resolution be sufficient to make a single 'dodgy' pixel unnoticable?
    Also does anyone know what Panasonic's tolerance is on them before a projector is deemed faulty?

    P.S. Any help would be greatly appreciated as am dying of the wait to get into the projector scene for the first time :)

    Cheers
     
  4. Tempest

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    I would say a bad pixel (depending on how it's stuck/dead) would still be VERY noticable on even the 700 model.
    If you have a black screen and a bright pixel it's going to have to be minute before you did not notice it.
     
  5. martian1

    martian1
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    Slightly off topic but i bought a camera last week with the lcd screen turned on yesterday and it had a bright green pin prick..dead pixel. I couldn't live with this on a 1.8 inch screen never mind one 7ft ! You just want to try and rub the thing off but it obviously it wont shift.
    This is bugging me as i was going for a LCD projector, i thought that once the thing was up and running without dead pixels that was it you were safe. Now how would you stand if one snuffed it after a couple of weeks, i would sit there waiting for the grim pixel reaper :eek:
     
  6. LV426

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    To answer your question, it depends on how "dead" it is. My Sony VW10 has had one misbehaving green pixel from new. However, it isn't fully on all the time; it's brightness varies but it never goes completely dark. Therefore, it is visible on black.

    However - viewing from about 12 ft away from an 8ft wide screen, it's so tiny as to be undetectable - even though I know where it is. I have asked visitors to find it (without telling them where to look) and no-one can.

    The resolution of the Panasonic 700 is only slightly coarser than the VW10 and I'd contend that a single failed pixel, if not close to the centre, will probably not be hugely noticeable.

    However, you could (and should)

    a) buy from a bricks and mortar retailer who will let you check your machine before you pay for it OR
    b) buy from somewhere who will check it for you and are prepared to rectify it if there's a problem OR
    c) buy by Internet or Phone but be prepared if necessary to exercise your legal rights under the Distance Selling Regs to return the product within 7 days for a refund.....

    just to be sure.
     
  7. mhouston

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    Cheers nigel...I'm a poor graduate in my first job who's trying to afford his first projector...I'm having a tough time deciding between buying from the cheapest place I can or from a place who do a DPC.
    I think the difference in price will be about £200 which is no small amount to me but I don't want to go for the cheap one only to discover a couple of dead pixels spoiling my enjoyment of my new toy
     
  8. LV426

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  9. LV426

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