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Gamma...

Discussion in 'Projectors, Screens & Video Processors' started by cyberheater, Oct 30, 2005.

  1. cyberheater

    cyberheater
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    I've had my PE5120 for some time now connected via component to a Limit SE900 DVD player running in progressive scan mode and have never really been happy with the results.
    The main issue was shadow detail. To get the blacks to be as low as possible I found the shadow detail was basically gone. To get the shadow detail back I've found i've had to raise the brightness level and thus raise the absolute black level. Not good.

    In desparation, also tried the PE5120 connected to my ibook G4 via VGA -> DVI-A. This combination gives you a lot more control over gamma settings.

    I've done some extensive testing over the last couple of weeks and here are my findings.

    1/ Using component feed/dvd player. The absolute black level floor is too high. If I feed a freeze frame of a black image from the Limit SE900 dvd player to the pj and switch from widescreen mode to 4:3 mode. The pillar box bars (left and right) are still darker then the central 4:3 image. This means is really annoying and prevents you getting the blackest black.
    Of all the modes, 'Cinema' gives the darkest blacks.
    If I reduce the black level so there isn't a huge difference in black level between the central 4:3 and the side bars, my shadow detail is lost. This should not be right.

    2/ If I use my ibook there is a utility where I can tweak the gamma curve profile. I managed to find a setting that looks fantastic.
    I can get deep blacks. The shadow detail is all there and the bright parts are where they should be.

    It does not matter what I do. I cannot replicate the settings using the component/dvd combination. The vga/ibook gives a far more impressive picture.

    Why don't dvd players allow changes to the gamma curve. Maybe some do.

    One more thing. I've watched a few movies using the vga/ibook combination and i've not had to tweak the projector settings once. :eek:
    This has never happened before. I've finally got a combination that i'm happy with.
     
  2. Gary Lightfoot

    Gary Lightfoot
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    Hi John,

    Very interesting read - thanks for taking the time to post it here.

    Did the utility allow you to adjust the gamma at the lower IREs to get the black detail visible without adjusting the lowest IREs and raising the black floor?

    Dod you measure the gamma curve before and after? Plot a graph with IRE at the bottom and the lux figures on the side, and see how the graph goes. You may be able to use the lux readings in place of the Y readings on the Excell spreadsheets in the SpyderTV thread and that should plot the curve for you. I've not tried it but it would be interesting to see how the plot goes and how the spreadsheet interprets the results (i.e what overall gamma value you get).

    I've not had any luck sourcing another light meter by the way, but will let you know if I do.

    Gary.
     
  3. cyberheater

    cyberheater
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    Thanks Gary.

    I feel guilty holding on to it. Do you want it back or I can pay for it. Your choice mate :)
     
  4. Gary Lightfoot

    Gary Lightfoot
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    If you're making good use of it at the moment, you can keep hold of it a bit longer. I haven't decided which choice to make yet. :)

    Thought about trying the SpyderTV?

    Gary.
     

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