Kodak DX 4530 Compression Algorithm Question

Discussion in 'Digital Photography' started by Glenn Nelson, Sep 24, 2003.

  1. Glenn Nelson

    Glenn Nelson Guest

    I just bought a DX 4530 (5 MPixel) and was surprised - and alarmed -
    to see that a typical image - at "Best" setting - was about 800 KB
    file size. My Casio 3 MPixel camera puts out 1.2 MB file size.
    Detailed comparison leaves no doubt that the Kodak image has better
    resolution. Now what I need to do is compare Kodak to other 5 MPixel
    cameras. Also Kodak puts out a 3 MPixel image which occupies around
    700 KB file and is still much better than my Casio. Other digital
    camera users tell me that their "best" quality images are typically
    60% smaller than the actual pixel size, so Kodak is clearly
    compressing more - but how?

    Does anyone know if Kodak uses some sophisticated variation of JPEG
    that happens to provide greater compression without loss of image
    resolution? Or did Kodak just crank up the compression in order to
    make smaller files?

    I like the feel of this camera. The controls are simple, yet versatile
    enough for most use. Using AA batteries is a BIG plus. I wish exposure
    compensation (plus/minus) was tied to buttons and not buried in a
    menu. And many things are missing - no color balance, no panormaic
    mode (stitching photos together), no thumbnail display.
    Glenn Nelson, Sep 24, 2003
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  2. (Glenn Nelson) wrote in @posting.google.com:
    I would imagine they just crank it up.

    So why is the Kodak better? One possibility: Quality of image is not only a
    function of compression; it's also a function of the camera's ability to
    capture a good image. A good lens and a good CCD help. A less compressed
    image captured with a lower quality camera could easily not look as good as
    a more comprssed image captured with a higher quality camera.
    Constantinople, Sep 24, 2003
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  3. Glenn Nelson

    Ron Hunter Guest

    There are a number of different approaches to compression, some of which
    give faster compression times, and use less CPU time, and others which
    take longer, but compress better, and use more CPU time. Every
    manufacturer likely implements the compression in a slightly different
    way. It is also possible to buy a chip that does this job itself and
    doesn't need the services of the main processor in the camera, but at
    considerable added cost. Whatever the Kodak approach, they seem to get
    good compression ratios and to produce pictures which have minimal
    compression artifacts. Good job, Kodak.
    Ron Hunter, Sep 24, 2003
  4. Glenn Nelson

    Glenn Nelson Guest

    Hmmm, my next step will be to compare against other 5 MPixel cameras -
    I'm planning to compare to Sony DSC-V1. I want to print 13x19, so
    differences may be visible.

    I am hoping that someone can definitively say how Kodak obtains such
    small files and whether or not it's a good thing. I know that Kodak
    has wavelet compression available in JPEG-2000, but I can't tell if
    this camera uses JPEG-2000, and if it does, I still wouldn't know if
    they've included wavelet compression for this model. Certainly there
    are variations on more conventional JPEG algorithms, but I would
    expect these would be widely used and therefore other manufacturers
    would also be outputting smaller files (maybe they do, I only have a
    few data points).

    Others have pointed out that the CCD and lens are also important in
    quality. While true, I would assume that manufacturers such as Canon,
    Nikon, Sony will all be comparable and only extreme magnification will
    show differences in resolution (color balance is a different matter);
    also extreme magnification will bring out differences due to the JPEG
    parameters. However, if different file size is simply due to cranking
    up the compression, I expect that quality would suffer at lower
    Glenn Nelson, Sep 24, 2003
  5. Glenn Nelson

    Ron Hunter Guest

    One of the realities of compression as applied to cameras is that the
    source data, that is what you photograph, has a lot to do with the
    actual compression obtained. The files on my Kodak 2mp camera range
    from 250k to 1.5 meg. Take a picture of a plain white wall and it will
    be quite small. Photograph a grassy field, and it grows dramatically.
    Ron Hunter, Sep 24, 2003
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