Do all DLPs have rainbows and do all LCDs have the screen door effect?

Discussion in 'Displays' started by Rolando, May 21, 2005.

  1. Rolando

    Rolando Screenwriter

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    Hi guys, just a quick question. Not trying to start another debate on which format is better. I have never even considered these before but I am starting to read up on them

    these 2 issues seem to come up all the time when the respective format is discussed so I wanted to ask:

    Are these issues that these formats are just prone to or do all DLPs have rainbows and all LCDs have the screen door effect. The only difference is some people see it, some don't and some don't care?

    In other words people who see rainbows on DLPs do you see them on all DLP models you see or are their just some models who have had this issue?

    same for SDE on LCD.

    thanks for the info!
     
  2. EricRWem

    EricRWem Screenwriter

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  3. Rolando

    Rolando Screenwriter

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    thanks for the link.

    As you can probably guess though I am already keeping tabs on that thread.
     
  4. Leo Kerr

    Leo Kerr Screenwriter

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    The short of it is:

    All digital projection systems have a 'fill factor.' DLP fill factor is somewhere in the neighborhood of 92%. D-ILA has a fill factor somewhere near 97%. LCD varies anywhere, it seems, from about 50% to 87%. (The 50% is a slight exaduration.. I haven't seen any quite that bad.)

    Fill factor is, in essence, if you took the screen area - say, 500in^2 - and found out how much was being illuminated by pixels rather than inter-pixel gaps, you'd get a number. 100% would mean no gaps between pixels. That's not how they measure it, but it'll do for an explanation.

    Rainbow effect is a feature of any single-chip display. Any single-chip DLP projector, D-ILA projector, or whatever, will exhibit the rainbow effect to some extent, because it's only illuminating the screen with one color at a time. Sizse, contrast, color wheel speed, and numerous other variables determine how much effect you might get at any given time. Then you add in the human effect - some people only see it rarely; others not at all, whilst others still almost constantly.

    3-chip DLP projectors, unfortunately, are out-of-reason expensive.

    Leo Kerr
     
  5. EricRWem

    EricRWem Screenwriter

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    Leo,



    Stupid question: The fill factor percentages you give...is higher or lower "better?"
     
  6. George_W_K

    George_W_K Screenwriter

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    A higher percentage is better.
     
  7. Kevin C Brown

    Kevin C Brown Producer

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    One thing to add: all LCD and most LCoS RP displays use 3 chips. So ... no Rainbow Effect.

    There is also a "Screen Door ..." thread over on AVS too, where someone actually calculates viewing distances for ED and HD plasmas and LCD flat panels to avoid SDE.
     
  8. Leo Kerr

    Leo Kerr Screenwriter

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    LCDs didn't always use three chip engines... but I've seen 'em that used single-full-color-panels - like a conventional direct view plasma/LCD/CRT display. Not good, but it has been done.

    I included LCoS/D-ILA in the list of potential rainbow machines because all of the early D-ILA RPTVs I saw were single chippers. Since then, that seems to have gone away.

    Leo
     

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