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purple image ????

Discussion in 'Projectors, Screens & Video Processors' started by rich07, Oct 14, 2003.

  1. rich07

    rich07
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    Hi, need some help with a second hand projector i just bought. It's an ex demo Infocus LP740, it did'nt cost me very much money but i'm just wondering if i can improve the performance without spending shed loads of cash on it???
    The problem is that below and above the picture projected, the border is purple, this is also evident on darker scenes on the image which is projected, say a night scene in a film where instead of being black it is slightly purple???? Any ideas what the problem might be?? thanks Rich.
     
  2. gothmog

    gothmog
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    Heh, quite a beast you have there.. nice resolution shame about contrast ratio :(

    The contrast ratio is roughly speaking a measure of the full on/off ratio of the LCD panel in conjuction with the brightness of the projector it dictates black a black the projector can achieve, 100:1 is terrible by todays standards, and this is probably why you can see the purple light breaking through in dark scenes there isn't much you can do except maybe add a filter to block the purple but really this is going to be a pretty poor projector for home cinema work :(

    If the damage is not uniform then it's probably heat damage to the optics which pretty much makes it wheely bin ballast.

    -- Jon
     
  3. rich07

    rich07
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    cheers Jon, a couple of my friends spent a few thousand pounds on there projectors and they are A1. I can't really complain as I only paid 250 quid and it's given me a start in the home cinema field.
    The picture is good, just a bit purple on some of the darker scenes but mainly round the borders. I took it apart last night to see if there was any serviceable items like a filter but couldn’t see any. How would you go about adding a filter? DIY job? Might not get back to you tonight as i'm off home now but any help is appreciated
     
  4. theritz

    theritz
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    Hi and welcome to the forums.......:hiya:

    Many use FLD (Flourescent Daylight) filter to correct the green tinge that is apparent in lots of LCD images, you could also try using a ND (Neutral Density) filter - this is a filter which is used to reduse the amount of light without affecting the colour reproduction. these are both types of photographic cilters, so effectively you should be looking for one which will fit the lens of the PJ (assuming it's got mounting threads for filters) or one which will fit snugly just inside the edge of the lens on the PJ (maybe with a little help from masking/electrical tape/whatever...)

    It really depends on the light output of the projector - if it's very bright, then using a ND filter (they come in grades, indicating how much light they reduce -- google for info from photography supply shops) could improve the contrast. The purple tinge could be from imperfections in the prism/optics - or it could be heat damage, difficult to tell without seeing it.

    It's probably worth a try - depending on how reasonably you can source the stuff. Some photography places sell secondhand filters etc., it might be worth a try at that level to see how you get on.

    Some searching on the forum (and the obligatory visit to the FAQ - top topic on this forum page !) should yield you more info.

    All the best,


    Sean G.
     
  5. rich07

    rich07
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    Thanks for all the advice, I'll search through the archives as you recommend and see what I can come up with.
     

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