Rainbow effects and headache etc with DLP – Advice please

Discussion in 'Projectors, Screens & Video Processors' started by Cas141, Sep 11, 2002.

  1. Cas141

    Cas141
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    I am looking to buy my first projector . I have read that the downside to DLP is the rainbow effect and headaches after an hour or more viewing for SOME people.
    Is it that the technology affects some persons’ eyes and never others; or is it that it depends on the make of the machine.
    Or another way – If I go and look at a DLP machine for a while and find it doesn’t affect me, will I get the same non effect on viewing other DLP machines- or could I get the effect if I use another make of DLP machine.
    Please answer if you know; if you are not sure, please don’t speculate.
    I am having difficulty getting demos of machines. However, if I demo one DLP I’d like to know if I can be confident of others giving me the same result.
    TIA.
     
  2. Jeff

    Jeff
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    Rainbows are people, projector and content dependant.

    Some people don't see rainbows at all regardless.
    Some people don't see rainbows on some projectors regardless of content.
    Some people see rainbows all the time regardless of projector or content.
    Some people see rainbows but it doesn't bother them.
    Some people don't see rainbows but still get headaches from watching DLPs.

    Someone at the Event last year even claimed to see rainbows on CRT projectors. :eek:
     
  3. Kramer

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    I sometimes see rainbows after a shower of rain (on a sunny day - so see none this summer :D ).

    Can't see I ever suffered from headaches as a result though.

    See rainbows after exiting nightclubs also, but also suffer headaches on these ocassions :mad:

    Am seeing rainbows now actually, even though it's dark :confused: (might be drink related :D ).

    Joking aside, fully endorse the previous posters assertions.

    Go see a DLP, or several - you'll answer you own question.

    I don't think anyone can tell you how they'll be for you.
     
  4. petrolhead

    petrolhead
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    Just an observation.

    The problem as I see it is that even though you may demo a DLP PJ for 20 Mins it may not answer you question as, as you have said, 'After an hour or more'

    So you may be fine in the demo but then getting it back home a watching a film you may relise that it affects you.

    PS - Funny, Kramer :)
     
  5. LV426

    LV426
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    Different DLP PJ's use variations of the colour wheel technique to generate full colour images. Some wheels have more colour segments than others (and the DLP chip is refreshed faster); some spin faster (and the DLP chip is refrshed faster) than others. Some do both. In general, the faster the colour refresh (ie more segments, faster spin) the less likely you are to be affected.

    So, if you see, and are affected by, rainbows on one DLP PJ, it doesn't follow that you will be similarly affected by others. Look for statements like 'six-segment wheel' (or more) and/or double speed (or more).

    The visibility of rainbows is affected by the amount of contrast or brightness in the image - dark, low contrast scenes won't reveal it as much as bright, contrasty ones.

    Every person's perception differs, too, and it can take some people some time to be affected. So, when evaluating, you should ensure:

    a) that you spend at least an hour undisturbed concentrated watching something with plenty of brightness and contrast - animations are probably a good bet.

    b) ensure that you are accompanied by anyone else who is likely to share your cinema with you - your partner for example - to ensure that they aren't going to be affected.

    Finally, you should try and audition one of the better LCD devices as an alternative - eg the new Sony VW12 if you can find one. This is claimed to offer near-CRT performance but with the convenience of a single lens device and no risk whatever of rainbow or other refresh issues.
     
  6. Corleone88

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    I own a Plus Piano 3100 (speed 2x and 6 RGB). I am very very sensitive to the rainbow effect (my wife too). The only way I found to get rid of with my DLP, is to connect my Piano to a HTPC on the DVI input (60Hz or 75Hz refresh rate). First, the picture is amazing and there is no rainbow anymore. Otherwise, you have the Sharp Z9000 (speed 2.5x) which is even better, but also much more expensive. My advice will be: try before buying with movies like Gladiator or Seven.
    Cheers

    Philippe
     
  7. Cas141

    Cas141
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    Thank you all for your advice. Since posting i have read that moving your head a lot can more likely induce this effect.
    Pity that, cos my main use of PJ will be flight sims and i will, of course, be looking around me for bandits:) Using a mouse substitute to move this view involves movement of the head,
    It's called Track IR for those of you who may know about flight sims. ( sorry to bore you )!
    so maybe LCD will be the answer.
    Anyway - will seek demos etc
    Thanks again
     
  8. Jeff

    Jeff
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    Unless its night flying you are unlikely to see rainbows in a flight sim.
     
  9. LV426

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    Definitely. I'm sorry I didn't mention it. A single-chip DLP image isn't actually in colour. It is a sequence of tinted monochrome images - ie. is blue, then green then red, then blue again etc...(perhaps not in that exact order). Your brain supposedly merges the three colours together and so you perceive a colour image.

    As you move your head (or as an object on the screen moves) you momentarily see, on either its leading or trailing edge, the three colours. This is the DLP rainbow.
     
  10. rob_w

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    I've got a dlp pj that has rainbow probs (plus u2-870)

    however, i can say.....

    1: never see 'em on quake3 arena
    2:have made my screen nearer the "optimum" size (2.5 x width = viewing position) - stops you moving your eyes around image when youre watching - still 5 foot wide screen)
    3:demo with a black and white film, or aliens has a good bit with white strip lights against a dark background - this is where rainbows are most apparent.
    4:anime doesn't seem to suffer as much - don't know why..
    5:if you demo with a hcpc, just wiggle your mouse about fast on a black background - very easy to spot rainbows there..
    6:ntsc dvd's seem less affected

    If you look for them you'll find them, however! if the film/games any good you'll be concentrating on that and not the rainbows

    hth

    Rob
     

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