How does gamma correction reduce noise?

Discussion in 'Digital Photography' started by Gregory Wool, Nov 15, 2006.

  1. Gregory Wool

    Gregory Wool Guest

    Hi,

    I read in an old thread that gamma correction does reduce the
    quantization noise in an image by pre-emphasising and de-emphasising
    like Dolby does on analog audio. As my understanding of that topic is
    rather poor can someone please explain to me how that works?

    Many thanks!
    Gregory
     
    Gregory Wool, Nov 15, 2006
    #1
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  2. Gregory Wool

    Greg \_\ Guest

    In article <>,
    "Gregory Wool" <> wrote:

    > Hi,
    >
    > I read in an old thread that gamma correction does reduce the
    > quantization noise in an image by pre-emphasising and de-emphasising
    > like Dolby does on analog audio. As my understanding of that topic is
    > rather poor can someone please explain to me how that works?
    >
    > Many thanks!
    > Gregory


    The more you (block up )darken shadows the less apparent noise....but
    the same idea throughout the image. Shorter contrast scales limit the
    values to blacker and whiter- Not always better.
    --
    "As democracy is perfected, the office represents, more and more closely,
    the inner soul of the people. We move toward a lofty ideal. On some great
    and glorious day the plain folks of the land will reach their heart's desire
    at last, and the White House will be adorned by a downright moron."
    - H. L. Mencken, in the Baltimore Sun, July 26, 1920.


    Reality-Is finding that perfect picture
    and never looking back.

    www.gregblankphoto.com
     
    Greg \_\, Nov 15, 2006
    #2
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  3. Gregory Wool

    Mike Russell Guest

    "Gregory Wool" <> wrote in message
    news:...
    > Hi,
    >
    > I read in an old thread that gamma correction does reduce the
    > quantization noise in an image by pre-emphasising and de-emphasising
    > like Dolby does on analog audio. As my understanding of that topic is
    > rather poor can someone please explain to me how that works?


    It's a good analogy. Gamma encoded images allocate more bits to the darker
    parts of the image, which are more prone to quantization. This is similar
    to Dolby's analog process, which boosts (pre-emphasizes) the high
    frequencies when recording to tape, and does the opposite when playing the
    tape. This retains high frequencies and at the same time reduces the amount
    tape hiss, which is not boosted.

    It's important to distinguish between quantization, usually seen as banding,
    and detector noise. Gamma encoding does reduce quantization and banding.
    It does not reduce detector noise because it treats noise and data
    identically,.
    --
    Mike Russell
    www.curvemeister.com/forum/
     
    Mike Russell, Nov 15, 2006
    #3
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