Re: Compression vs. Resolution (Pentax Optio S)

Discussion in 'Digital Photography' started by matthews, Jul 23, 2003.

  1. matthews

    matthews Guest

    William M. Miller wrote:

    > According to the Optio S manual, the size of a 2048x1536
    > photo stored in their maximum compression JPEG is just
    > about the same as a 1600x1200 stored in their medium
    > compression format. Which of these would you expect to
    > look better?


    For a given file size, more compression and more resolution
    generally beats less compression and lower resolution.

    See

    http://www.wfu.edu/~matthews/misc/graphics/ResVsComp/JpgResVsComp.html

    Rick Matthews
    matthews, Jul 23, 2003
    #1
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  2. "matthews" <> wrote in message
    news:bfmt38$msu$...
    > William M. Miller wrote:
    >
    > > According to the Optio S manual, the size of a 2048x1536
    > > photo stored in their maximum compression JPEG is just
    > > about the same as a 1600x1200 stored in their medium
    > > compression format. Which of these would you expect to
    > > look better?

    >
    > For a given file size, more compression and more resolution
    > generally beats less compression and lower resolution.
    >
    > See
    >
    > http://www.wfu.edu/~matthews/misc/graphics/ResVsComp/JpgResVsComp.html


    Thanks! That was a very helpful analysis.

    -- William M. Miller
    William M. Miller, Jul 24, 2003
    #2
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  3. matthews

    Troy Chinen Guest

    matthews <> wrote in message news:<bfmt38$msu$>...
    > William M. Miller wrote:
    >
    > > According to the Optio S manual, the size of a 2048x1536
    > > photo stored in their maximum compression JPEG is just
    > > about the same as a 1600x1200 stored in their medium
    > > compression format. Which of these would you expect to
    > > look better?

    >
    > For a given file size, more compression and more resolution
    > generally beats less compression and lower resolution.
    >
    > See
    >
    > http://www.wfu.edu/~matthews/misc/graphics/ResVsComp/JpgResVsComp.html


    Just a couple of comments:

    1. At extreme compression levels where blocking artifacts are clearly
    evident, the lower resolution scheme is generally preferable. This is
    the approach that JPEG 2000 takes, and it outperforms JPEG quite a bit
    at high compression ratios.

    2. JPEG is generally visually/perceptually lossless at about 20:1,
    when printed at 300 dpi on normal photoprocessed prints. Even at the
    highest compression setting on the optio s, the compression is less
    than this. In other words, even at the worst quality setting the
    artifacts you will see in print are due to the camera and not the
    compression. The caveat is that on monitor you will see artifacts
    more readily. However, most people are unlikely to view images at
    full res on screen simply because they won't fit; the downsampling
    process is likely to mitigate some of the effects of compression
    artifacts.

    3. I just purchased the optio s and I love everything about
    it....except the image quality: too much noise on indoor shots. The
    noise combined with the Bayer filter array interpolation causes a lot
    of ugly noise. But I'm probably more sensitive to this kind of thing
    because I used to evaluate image quality for a living....
    Troy Chinen, Jul 25, 2003
    #3
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