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radar
Joined: 05 Dec 2007
Posts: 72
Location: Sydney, Australia
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| Posted: Tue Jul 15, 2008 11:49 am Post subject: Is it possible to change the contrast on blue only? |
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Hi,
I have a barco data 701. The blue tube is probably a 7.5/10. With the contrast turned down enough so I can look through the lens, the red and green tubes seem to have good contrast, but the blue tube does not seem to have good contrast. The black parts on the screen do not go black on the blue tube, but do on the red and green. One would think I had the blue tube turned up too high on the brightness, which I don't. Is there a way (maybe a trim pot change?) to alter the contrast on the blue only? Or... which I hope is not the case... the blue tube needs to be replaced? It is a Sony 07ms 700lm tube.
Here's hoping... Kevin.
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Tue Jul 15, 2008 12:44 pm Post subject: |
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Sounds like you need to do a grayscale adjustment. Just to avoid confusion: "blacks not going black" is not a problem of the CONTRAST setting, but of the BRIGHTNESS setting -- and the Drive or Gain controls and the G2 or other black-level controls. Because your blue is not cutting out when the other colors do, you're probably getting color errors in the low brightness levels, and probably have other problems too.
See Kal's exceptional grayscale tutorial at https://www.curtpalme.com/forum_archived/viewtopic.php@t=10457.html . Even if you don't go whole-hog and get a colorimeter &etc, you will still learn a lot that will help you understand what's going on and probably improve it just tweaking it by eye.
Gary
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radar
Joined: 05 Dec 2007
Posts: 72
Location: Sydney, Australia
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| Posted: Wed Jul 16, 2008 1:04 pm Post subject: |
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Ahhh... yup. I thought I checked the G2, but it was out on the blue (too high). Now I have other issues... but thats ok... I just need to buy one of those Box1040's to fix it! I'd love to see more detail in the dark bits!
Thanks!
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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| Posted: Wed Jul 16, 2008 2:47 pm Post subject: |
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While not everyone seems to agree, I have yet to see ANY crt projector that doesn't need some form of external gamma boost to get the gamma curve right.
Those that don't think they need a gamma boost have never actually measured their gamma curve. They may think it looks fine but that doesn't make it right. (My guide that Gary linked to gets into this...)
Kal
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