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Dead pixels / sticking pixels ?

Discussion in 'Projectors, Screens & Video Processors' started by yellowbug, Apr 27, 2004.

  1. yellowbug

    yellowbug
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    Is the problem of dead pixels or sticking pixels only relevant when you first buy your PJ or can they develop over time? If so, how widespread is the problem, as this may tip the balance for me in favour of DLP. I have not managed to find any info on this elsewhere. It terrifies me that LCD PJ manufacturers won't consider it a fault unless it gets to quite nasty proportions, as it would annoy the heck out of me.

    Ade
     
  2. Kramer

    Kramer
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    Most LCD pixel defects are there from manufacture. Pixels can fail during use but this is very rare IMO.

    DLPs can have faulty mirrors although again, this is extremely rare.

    Two options when purchasing an LCD:

    1. Buy from a dealer with a pixel check/guarantee
    2. Take your chances.

    :smoke:
     
  3. Spasm

    Spasm
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    Dead pixels can either be apparent from the off set as Kramer suggested or develop over time:

    They are either seen as "dead" pixels displayed as black and "lit" pixels that are white:

    This occurs as each pixel on an LCD screen is made from three separate subpixels—one red, one green and one blue—that when combined form the colours that the users see on the screen. A dead pixel occurs when the transistor that activates the amount of light that shows through all three subpixels malfunctions and results in a permanently dead/ilt pixel.

    DLPs can get stuck pixels although this is very rare so I wouldn't let this bother you.

    With regards to LCD - most dead pixel warranties follow a simular precesure. Split the screen into nine equal squares. You are allowed up to 8 dead pixels as long as there are no more than one in the central square. Any more and the projector can be fixed under warranty.
     
  4. Liam @ Prog AV

    Liam @ Prog AV
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    Dead pixels developing over time are more common than you might think, more likely during the first 6 months or so of use....

    With LCD pixel policies you'll find each manufacturer has their own way of doing it. Most have a simple 0.01% tolerance - useless really seeing as that's around 40 pixels on even the lowest resolution PJs!

    Then there are the weird rules pertaining to location on screen and in relation to other pixel defects - some manufacturers will accept fault if there are "clusters" of two or more pixels in certain locations and some even go into location of "clusters" in relation to other clusters! IIRC Panasonic take into account location of screen (4x4 grid of inner 4 and outer 12), colour of defect, location in relation to certain other colour defects, and if those defects occur as clusters or not and what their location is relevant to other clusters of a certain colour!!!! Of course if you phone Panasonic up three times in a row and ask for their policy i'll bet you get three different answers :laugh:
     
  5. Gary Lightfoot

    Gary Lightfoot
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    Sim2 checks all DMDs for mirror function/failure prior to shipping (amongst other things), and combined with a 3000hour/12month lamp guarentee, I believe they're the pj leader for ensuring you get the image you pay for.

    Gary.
     
  6. yellowbug

    yellowbug
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    Well thanks for clearing that up then!

    Interesting to hear that DLP's can have stuck mirrors too. BTW I am now looking seriously at buying the Panasonic AE500 (although their policy in this regard does sound rather strange, clusters and all that stuff), subject to forthcoming demo. I will be looking out for the vertical banding issue I've read so much about, but then all PJ's seem to have an issue of one description or another!!

    Now, over to the DVD player forum to see if I can find out which player is going to give me the dvi output I'll be needing for the 500...

    Ade
     
  7. LV426

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    Whilst not wanting to deny what Liam says, the likelihood of a PJ developing new bad pixels after manufacture is honestly quite rare. The thing to do, IMO, is to thoroughly check YOUR projector when you collect it. Get them to use its test modes to show you each of a fully black, red, green and blue image and inspect it for defects. Get one which is defect free from new (they are, mostly) and it will in all probability stay that way.
     
  8. yellowbug

    yellowbug
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    Sounds like the best bet to me. I haven't been to this dealer before so I don't yet know if their demo room will be light controlled (I doubt it), will I be able to spot defective pixels if there is ambient light?

    Thanks
    Ade
     
  9. Mirablo

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    it is more tricky but as long as its fairly dary and you can look at it on single colour screnes. most importantly Black blue and white imho as this should show up the most annoying of the pixels lit blue, lit green on the dark scenes and the dead or perma off pixels on the light scene. rmember to look hard before you buy then just enjoy the PJ once you have bought :)
     
  10. zoolap

    zoolap
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    Anyone know how thorough discounttv are in regards to pixel checks as I see they do a dead pixel check.
     

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