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No information in darker areas

Discussion in 'Projectors, Screens & Video Processors' started by henry1234, Feb 18, 2003.

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  1. henry1234

    henry1234
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    Things are going well and my hcpc is up and running nicely. I have set up the projector (NEC 6PG) and feed it a 720p signal, which it resolves nicely.

    The problem is that although things look fine on my PC CRT monitor, when I switch to the projector the image needs extra gamma/brightness and contrast (via overlay controls) to show the same picture information in dark areas.

    After these settings the picture looks washed out and over contrast. But it's the only way to see the darker picture information.

    The cable is only 2metres so I don't think it could be that, but I need a 25ft cable soon.

    The card is a Radeon 9500 Pro. I assume it outputs the correct voltage needed for the projector?

    Is it possible I need a VGA line driver to increase the voltage.

    The image looks to me as if I am wearing a pair of lightly tinted sunglasses.

    Any ideas as to the problem?

    (the PJ is set up, maximised rastors, well focused and converged, square on to the screen, brightness and contrast at default levels and colour balance all default 50% until I get it calibrated)
     
  2. CogPaul

    CogPaul
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    Hi Henry

    I have been looking into this issue in relation to scaler output and one solution is to increase voltage on the signal into the CRT - some projectors prefer a higher voltage than the standard 0.7v pp output by many scalers and video cards. You can change the voltage on modded cards like the KBK type(details on the avscience forum) or alternatively many people appear to use interface units ( eg. extron202+/xi or 109+/xi) which allow you to increase voltage - if you do a search on the avscience forum under extron you will find the relevant info. Be warned these units are very expensive new ( £1100 or 750) but can be picked up on e-bay for around $100-250 plus postage- i have just ordered one and will let you know if it solves the problem
     
  3. henry1234

    henry1234
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    Paul,

    Thanks for the info. I would like to know how you get on. Did you buy one from ebay USA?

    This is a long shot but:

    Could it be that if a projector had been used with an amplified signal in the past that there is some setting deep in a service menu telling it to expect, say a 1.0v signal instead of a 0.7v signal.

    If I swith my desktop crt monitor to expect a 1.0v video signal input the picture dulls and looks near identical to what I see on my pj.

    Any chance you can ask at work how they feed the PJ's in the past or even how they fead those Sony's you want so much!

    Did they ever amp the signal or just run a straight VGA-BNC cable from a P.C. I'm guessing they probably used an NEC swithcer unit.

    Incidentally the specs from the service manual say:

    RGB 0.7Vp-p
    H/V sync 0.7 to 4.0Vp-p

    Would amping above 0.7v help the picture info?



    Regards,

    Henry
     
  4. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Most of these were used with NEC switcehrs I'd think. If you want to try one and Paul doesn't have one I do. Would be happy to lend it to you for testing if you paid postage.

    Gordon
     
  5. CogPaul

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    Hi Henry

    to the best of my knowledge there is no user adjustable setting within the projector that can be adjusted in respect of the input voltage. The Nec's were fed via broadcast quality switchers - not sure of manufacturer . The Sony's are fed direct from a Silicon graphics computer which has the most amazing video card I have ever seen! Some projectors like Electrohomes apparently prefer nearer to 1v signals - and I have been advised to try an extron to up the voltage - I would imagine Gordon or Roland would be better placed to offer some info/guidance on the wisdom of this?
    If you try a composite feed to the crt and it brightens the picture - remember composite signal is nearer to 1v - then you can probably safely say it is an input voltage issue.

    Yes ebay USA is a good source for extron gear

    Paul
     
  6. henry1234

    henry1234
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    Here’s my progress so far.

    I looked into the rastors to see the missing picture on my test piece and the phosphor was totally void of info in the darker areas. (when radeon set to default)

    On my P.C monitor the picture detail is clear as a bell, so I know its there.

    The same applied to composite and s-video from my DVD player. Although the rastors revealed a tiny bit more information with this feed it was hardly anything.

    When I set the auto colour balance the picture suddenly become brighter and the detail is revealed for a split second before dimming down again and hiding the detail.

    I remembered that before I reset the projector I wrote down the original colour balance settings:

    W B
    R +59 +54
    G +55 +83
    B +60 +60

    I put these back in and hey presto I can see all the missing picture info in the darks when looking into the rastor.

    So after all the fuss it was my white balance levels.

    However, now I've upped the white balance settings the composite feed from my DVD player despite being interlaced is much brighter, with more contrast and all the black level detail compared to the HTPC.

    The problem now is that I don’t know how to set them up properly. If I up the settings on the Radeon then I need to lower the settings on the PJ. How do I know which is right and I have a reference setting from my P.C. That’s my next task.

    Gordon,

    Your offer didn’t go un-noticed. For the time being I hope I have solved this dilemma but thank you very much.



    I have been using 5th Elemement SupaBit 8min 57sec into film, the supreme being things walk into a darkened room. The fronts of them are dark but there is detail in there their face and belly’s can be seen.
     
  7. Roland @ B4

    Roland @ B4
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    If the detail is in the signal then uping the brightness will reveal if the detail is there. If the voltage is too low then the blacks will lift too.

    Are are you sure you have set your G2 levels correctly.

    the Extron boxes are good but there is a UK company called Procon who produce a far better box for around £400. I have used these a lot and have them in my demo room the build quality is next to none.
     
  8. henry1234

    henry1234
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    Paul,

    Although I seem to have solved my problem, I woundered if the Extron unit you bought has helped or improved anything else?
     
  9. CogPaul

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    Hi Henry

    not been able to test it fully yet as I am waiting for my Lumagen scaler - Gordon is coming to installl-calibrate so will post details then.

    Paul
     
  10. nfordenfield

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    Having been on the receiving end of a Roland tweek, i too would be suspisious of the G2 settings, mjy 1208 now resolves fine detailed blacks.

    Rgds

    Nathan
     
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