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Thread: Gamma Correction For YUY2

  1. #1
    Join Date
    Aug 2017
    Posts
    6

    Gamma Correction For YUY2

    Hello,

    I'm using the DFK 33UX265 and pulling frames in YUY2 format. This works well, however there appears to be a small change in lighting relative to when frames are pulled in RGB. In YUY2 dark objects look darker, and very bright objects appear slightly brighter. As a result, I think that the issue may be that the gamma for YUY2 isn't precisely the sRGB gamma of 2.2.

    Do you happen to know what might be causing this? Right now I'm applying an extra ~1.3 gamma to compensate by brightening up the dark areas, but I'd much prefer having a more precise correction if possible.

    I should also note that in IC Capture, YUY2 has the same lighting profile as RGB32. I only see the difference when pulling frames using the C++ SDK.

    Any advice or suggestions would be more than appreciated.

  2. #2
    Join Date
    Aug 2017
    Posts
    6

    Re: Gamma Correction For YUY2

    Ok, I believe the issue is because the colorimetry of the video is full-range YUY2, as opposed to the more common, but less precise, tv-range.

    After applying a linear mapping from the camera's [0,255] ranged data into [16,240] for the Y luma component and [16,235] for the UV chrominance component, the YUY2 video seems to look much more accurate.

    Would you happen to know what the exact colorimetry of the YUY2 is? As in, is the video full range ITU-R BT.601 or ITU-R BT.709, is the gamma linear or 2.2, etc.

    Additionally, it might be a good idea to include the color specification in the gstreamer caps. There's a colorimetry field that's supported by many plugins, although it's documentation seems to mainly be the source , at least at the moment.

  3. #3
    Join Date
    Jan 2003
    Location
    Bremen, Germany
    Posts
    4,893

    Re: Gamma Correction For YUY2

    We handled this case by email.
    Best regards
    Stefan
    IC Imaging Control Support

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