Rainbow Effect

Discussion in 'Archived Threads 2001-2004' started by Matthew Will, Mar 16, 2003.

  1. Matthew Will

    Matthew Will Stunt Coordinator

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    Here are some questions I have on the rainbow effect -

    1. Are there any websites that have animations that demonstrate what the rainbow effect is like?

    2. Does adding a progressive scan DVD player with 3:2 pulldown or line doubling help with the rainbow effect?

    3. Does seating distance help with alleviating the problem? If I sit farther away will it be almost nonexistant?

    4. This is going to be the most drastic question, but is it possible to buy an aftermarket computer chip and color wheel to enhance the DLP projector? For example, could I buy a 2X DLP projector and then buy a 5X color wheel and install it myself or have a Home Theater shop do it for me?

    I still am new to the rainbow effect so any info is greatly welcome. Thanks. Matt
     
  2. Doug_B

    Doug_B Screenwriter

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    Matt,

    1. Don't know, I haven't seen any.

    2. I have not heard of any case where the source equipment has had a primary effect on the ability to see (or avoid seeing) rainbows. Rainbows (and/or headaches) are really gated by the DLP single chip color wheel technology.

    3. Seating distance may help. If you're sitting at a distance that results in a large subtending angle of view where you are often moving your eyes back and forth to cover the entire view, this can increase the probability of seeing rainbows for some people that otherwise wouldn't detect them.

    4. No, I don't think so. The rate at which the wheel spins is intimately tied to the critical functions of the projector vis a vis the the DLP chip. This suggestion is akin to gutting the projector and starting from scratch (well, close to it, I suspect).

    I would suggest you try to get a few DLP projector demos, if possible with units of different wheel speeds. Bring some material that is reported to increase the probability of seeing rainbows. I believe scenes with large, abrupt brightness changes are supposed to be good, such as a dancing fire in the darkness. Movement of such objects may increase the chances as well. I would suggest viewing from a distance which you would most likely support in a future setup, and initial viewing should be casual. If you don't see them, you could try moving closer to the screen or darting your eyes back and forth during scenes of supposed higher rainbow probability. Also watch a movie for a lengthy time period to ensure you don't get any headaches (which have been reported without also seeing rainbows).

    One word of warning; if you don't see any rainbows with casual viewing, it may be wise not to try harder. If you do try harder and then discover them, you may have trained yourself out of being able to go back to casual DLP viewing.

    Doug
     
  3. Max Leung

    Max Leung Producer

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    Movies that are good for bringing out the rainbows:

    Fellowship of the Ring (opening battle sequence, Sauron getting ass kicked, opening of the Mines of Moria)

    Fight Club (any dark scene...particularly the support group scenes).

    Gladiator.

    Black and white movies, ie. Casablanca.

    One person on www.avsforum.com made an animated gif that showed what the rainbow effect looks like. Unfortunately, I can't seem to find it right now with the AVS search function.

    I have an NEC LT240, and am regretting the purchase because I can see them pretty badly, even in still images. I've got overly sensitive eyes (I have great night vision and can see monitor flicker up to 85 Hz) I guess. However, the LT240's rainbow effect isn't as bad as a Dreamvision projector I saw the other day, which also has a 2x color wheel.

    It took me a couple of hours for the eye-strain to go away when I first got the projector. No headaches. Bright movies I have no trouble with (like Fifth Element, romantic comedies, etc.), I hardly see any rainbows. Be aware of this when demoing DLP projectors.

    It's likely a rod sensitivity thing. Physiological. Whether or not it bothers you is psychological.
     
  4. EdR

    EdR Second Unit

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  5. Max Leung

    Max Leung Producer

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    I don't think there is any literature out there publically. I'm pretty sure Texas Instruments knows, but they ain't telling for obvious reasons!

    This thread on avsforum has a plausible explanation. Unfortunately, the poster lists no sources:

    http://www.avsforum.com/avs-vb/showt...postid=1861243
     
  6. Max Leung

    Max Leung Producer

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