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HS50 problem possibly:

Discussion in 'Projectors, Screens & Video Processors' started by hebawom, Mar 30, 2005.

  1. hebawom

    hebawom
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    Over easter, I built a screen with some 1.3 gain material and I built a high shelf for my projector which I got at perfect right angles. Very square image - very happy with it in everyway, except (and I didn't notice this previously), I have severe banding in dark scenes. Most annoying.

    It only occurs in very dark scenes when there isn't much light shining at the screen, so I thought it might be something to do with my screen, I inspected it, and its flat and smooth. I don't know much about the infamous vertical banding, but I've not heard of it being exclusive to dark scenes before. What could this be, and more importantly how can I get rid?

    Also, am I alone in this observation?
     
  2. Dwayne Dibley

    Dwayne Dibley
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    ....hmmm... I'm currently using an IKEA blackout roller blind as a screen, and the picture is great. Another guy, on the forums, had a similar problem as yours when he went to a proper screen...... maybe you could try one of these roller blinds, they're only 20 quid. Mine is 2metres by 2metres and works as a blind and screen in one.
     
  3. UrbanT

    UrbanT
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    What are your projector settings? (brightness etc)
     
  4. hebawom

    hebawom
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    Well, I did some testing after I saw this banding and I tried all the presets and user1 which is what I've found most pleasing to me: Low lamp, auto iris, 80 contrast, 50 brightness, colour temp middle, gamma 2. The bands were present with all settings, although the less brightness the less noticable the bands.
    I only see these vertical bands when there is a very dark scene or a completely black screen (ie iris totally closed).
    The bands are about 15-20 pixels across and evenly spaced across the whole image.
    I'm driving a 50hz singal through powerstrip via VGA. Perhaps the graphics card? I'm going to do more testing tonight and I'll take some pictures as well
     
  5. hebawom

    hebawom
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    OK, definitely figured out the problem (just not the solution!) - I have flickering vertical bands in regular intervals along my image.
    I messed in powerstrip a little bit and pretty much got rid of the lines by setting the refresh rate to 47Hz. This seems to have reduced the effect dramatically, are there any side effects of 47Hz?
     
  6. hebawom

    hebawom
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    Spent a lot of last night fiddling about with setting in powerstrip. I had no idea what I was doing, but through trail and error managed to get a 50Hz stable image. And like I said this does reduce the banding, but I then watched "Finding Neverland", and I kept seeing it in dark scenes. Maybe it has been there from the start and I've only just spotted it, but now I can't not see it.

    Could it be that my ATI 9600XT is not up to the job of pushing a signal down a 10m VGA cable?
    Any suggestions anyone?
     
  7. UrbanT

    UrbanT
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    Does the 9600XT have both VGA and DVI output? Are you connecting straight from the VGA if so? My 2 suggestions if you haven't done so, are:

    1) if you are connecting by VGA, use a cheapo DVI/VGA adapter (you may have got one with your card), and connect at the PC end via DVI
    2) buy a better quality VGA? (assuming you have a cheaper one?)

    Just random thoughts :)
     
  8. hebawom

    hebawom
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    yes, I have the dongle that came with the card - will try that, and the VGA was about 30 quid from lindy - I guess thats quite cheap!
     
  9. UrbanT

    UrbanT
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    I use the Lindy 'premium' 10m VGA/VGA cable that cost about £38 without problems. Try the dongle, that could help, its how I run mine
     
  10. hebawom

    hebawom
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    I'll report back tonight!
     
  11. hebawom

    hebawom
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    OK, just tried my dads 30 quid DVD player through composite video. Crud picture but absolutely zero banding. What a relief! My projector is OK. I then tried a shorter VGA and again no banding.
    I also have to 10 metre premium lindy cable so I can only think my graphics card - is it possible that it can't send the signal through that length?
    I'm thinking either a new graphics card, or see if I can get away with a shorter cable.
    Is this about the size of it? Any other suggestions?
    Oh, I tried going through DVI, but couldn't see ANY difference from the straight VGA.
     
  12. UrbanT

    UrbanT
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    Certainly no problem with the cable length, I use the 10m Lindy premium without problems. Do you have a friend who you can borrow another graphics card from to test?
     
  13. Paul D

    Paul D
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    Since you mention you might be able to use a shorter cable, does this mean you have "coiled" any excess?
    The reason i mention it, is sometimes this can introduce weird effects like ghost sync signals, and timing errors etc.
    Also. does your cable go anywhere near power cables? (this can also have an effect)

    You may find that you VGA card simply cannot power the cable, as different cards sometimes fail to drive long cables. :)
     
  14. hebawom

    hebawom
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    Interesting points there. I'll check for the excess cable behind my sofa tonight. I suspect it will be coiled.
     
  15. hebawom

    hebawom
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    Just for completion of this thread; I tested another PC through the 10 metre cable and the picture was great. I then swapped over the graphics cards (took out the ATI9600XT and put in an nVidia5700), to begin with I couldn't load windows and had to reinstall, but now I am very happy with everything. If anything I think the nvidia card produces an even sharper picture than the ati as well as completley emilinating the banding.
    Thanks for the advice given - may get a chance to watch some films now!
     
  16. Paul D

    Paul D
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    Good news :smashin:
     

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