bayer filter pattern array questions

Discussion in 'Darkroom Developing and Printing' started by Dale, Feb 13, 2014.

  1. Dale

    Dale Guest

    what device dependent RGB does the bayer pattern use?

    I know they double the green cells because the eye has more G rods or
    cones than RB

    does bayer assume rec709 video?

    bayer doesn't assume sRGB or ProPhotoRGB since those came much later

    why not have a sensor filtration that is CIEXYZ compatible? that way the
    camera can be easier to use in device independent color like
    http://www.color.org

    the preference of G cells in the bayer pattern I think can cause noise
    in places like hair, etc
     
    Dale, Feb 13, 2014
    #1
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  2. Dale

    Martin Brown Guest

    It doesn't have to use RGB at all! Another variant more commonly used
    for video sensors uses CMYG or CMYW and yet another Sony CCD used RGBE
    (E = emerald green/cyan). Kodak has also patented RGBW patterns. See

    http://en.wikipedia.org/wiki/Bayer_mask

    They are severely limited by the properties of light stable dye filters
    and the need to be able to physically manufacture the filter mask.
    Bayer specifies the pattern and a means to demosaic it back to YCbCb or
    RGB taking advantage of the predominance of G in the Y channel and
    limitations of the human eyes colour resolution capability. You are
    stuck with what the chemical dyes for red, blue and green can actually
    deliver in practice. Red is very good (but not always light stable),
    green is so-so and blue may have a small long wavelength red leak.

    Wratten filters being one set that is used in scientific work graphs:

    http://www.edmundoptics.com/optics/optical-filters/color-dichroic-filters/kodak-wratten-filters/1326

    Whilst insanely priced bandpass filters are possible they do not help
    perceived image quality in conventional colour imaging and would be all
    but impossible to manufacture on the scale needed for consumer CCDs.

    The demosaic into RGB or YCC can be done back to whichever colour space
    you want to choose and then embed the appropriate colour profile.
    It limits the resolution you can hope for when imaging in monochromatic
    red hydrogen alpha light or blue hydrogen beta, but apart from that it
    really isn't a big problem. You can design bespoke testcards that Bayer
    struggles with and Foveon fans spend all their time obsessing about it.

    In fact a bug in most JPEG decoders is much more of a hindrance for
    using monochromatic blue or red light for imaging with a Bayer mask.
     
    Martin Brown, Feb 13, 2014
    #2
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  3. Dale

    Alan Browne Guest

    Download dcraw.c and you'll get all sorts of data about bayer patterns
    in various cameras as well as color space application.
     
    Alan Browne, Feb 13, 2014
    #3
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