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DLP rainbows and PC images

Discussion in 'Projectors, Screens & Video Processors' started by Bursar, Sep 1, 2003.

  1. Bursar

    Bursar
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    We're looking at the possiblity of getting a DLP projector for work. It would be hooked up to a PC and used for PowerPoint presentations and other dull stuff like that.

    Previously we've always had LCD projectors, but the price difference between LCD and DLP can be fairly large, and price is all important to us.

    I'm aware of the possibility of rainbows, but I'm curious as to whether they affect static images in the same way as they appear on film.

    Is there anyone that can give it a test for me please?
     
  2. Anders_UK

    Anders_UK
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    The rainbow effect is not due to your source input, it is due to the way the single chip DLP optics work. If you are used to LCD projectors then I'm sure you are aware of the 'X-cube' that re-combines the 3 separate colours. Well single chip DLP is different, it relies on one TI chip doing the 3 images and to get the 3 separate colours there is a spinning wheel with different coloured segments on them, Red, Green, Blue and sometimes white aswell.

    The rainbow effect or colourbreak up is down to this colourwheel. The image on the screen, if you slow the whole process down is written 3-4 times a frame, by combining each of the seperate individual colour frames. The trouble is if you have fast moving images (like we have in military jet simulators) that the database images are just too fast for the wheel so when you trace, say another jet in a dogfight you actually see the different colour frames.

    In a powerpoint the fast moving images won't be a problem, same as most movies, the problem comes with your own eye. Becasue your eye can move across the image faster than the colour wheel you get the same effect. I don't see it being a huge problem, cause your viewers eyes won't be flying around the screen like they would when watching a movie or training to be a pilot.

    For the dissadvantage of the rainbows you will get a far greater image quality from a DLP than LCD!
     
  3. Bursar

    Bursar
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    Well that sounds OK, and is pretty much what I figured. Thanks.
     
  4. Kramer

    Kramer
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    That's a very broad/sweeping statement.

    Granted DLPs are better in some areas but LCDs can still produce better results. All DLPs are not equal :lesson:

    It's unlikely that black levels will be an issue for Powerpoint presentations (usually some ambient light) so don't discount LCD.

    One wouldn't want complaints after a long presentation about eye fatigue, rainbows etc...

    Pros & cons for either variety of digital PJ.



    :smoke:
     
  5. Bursar

    Bursar
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    This is very true, particularly as it would be taken out on the road and probably used in less than optimal conditions.

    After some discussion we've decided to for an LCD projector. The possibility of rainbows upsetting some important person whilst s/he's watching a presentation is something we can't really risk.
     

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