Canon A70 Q's: lossless rotation, JPG quality

Discussion in 'Digital Photography' started by Gary Fritz, Oct 17, 2003.

  1. Gary Fritz

    Gary Fritz Guest

    The A70 has a feature to rotate pictures inside the camera. Any idea if
    this is a lossless rotation? Or would I be better off to download the
    images and use a lossless tool to rotate them?

    Does anyone have any idea how much compression is used in the Superfine,
    Fine, and Normal modes, and how much it degrades the image? I'm assuming
    Superfine is essentially uncompressed and hopefully nearly as good as a RAW
    format. How much does the image degrade when you go to Fine? Supposedly a
    Large Superfine image is very good for 8x10 and "photo quality" (300dpi)
    for 5x7. Is a Large Fine image very good for 5x7, or...? What about

    Gary Fritz, Oct 17, 2003
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  2. Gary Fritz

    Zol. Guest

    I don`t think you will notice any differnce - I have done this both ways -
    the only thing that you must remember is that if you select to rotate in the
    camera then zoombrowser will rotate it automatically or you can have a copy
    rotated so you can comapre the images under a microscope :)
    I don`t know about what compression ratios that Canon use but the better the
    ratio (superfine) the better the images will look although fine will produce
    decent imagery and normal will give OK images for snapshots but don`t get
    confused with RAW files (uncompressed image file), these are not JPG
    files(compresed) and are not available on the A70.

    The only settings I used on my A70 were Large & Superfine - `Large` Images
    take up more space on the CF Card but they are more manageable and can be
    cropped or resized if used for other purposes like web images. and likewise
    the superfine compression gives higher quality at a slight file size


    "May you find what you are looking for in the Window at the heart of the

    My Photo Galleries -

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    Zol., Oct 17, 2003
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  3. Gary Fritz

    Gary Fritz Guest

    Obviously. I'm just trying to understand how much difference it makes
    without going through a whole lab experiment on my own. Surely SOMEbody
    has figured this out already!
    "Slight" !? Try nearly 100%! Canon's site says 893kb for
    Large Fine, 1602kb for Large Superfine. If it was a "slight" increase I'd
    always shoot at Superfine, but for most shots I can't justify cutting my
    "pictures per CF card" in half. If I'm setting up a "wow" shot I'll bump
    it up to Superfine, but most of the time I run it at Large/Fine so I can
    get 137 shots in my 128MB CF instead of 68.

    Gary Fritz, Oct 17, 2003
  4. Gary Fritz

    Zol. Guest

    I think the only way you are going to be happy is to do a test yourself (Ask
    a store for a demo and take a CF Card with you!) Typically for a 256Mb CF
    Card @ L/SF I could get about 192 Outdoor shots(Variable on image
    complexity) which is more than enough for most cases - CF Cards aren`t that
    expensive, treat yourself and you can keep the quality and image size! Zol.

    p.s. check out ebay or on-line stores for the best CF Card deals - Lexar CF
    Cards work great for the A70. (Z)
    Zol., Oct 17, 2003
  5. Gary Fritz

    gr Guest

    If it's like my C5050, all the rotate function does is set a bit in the file
    that tells image viewers to display the image 90 degrees (or 270) from the
    way it's written. Thus, it's lossless, because it doesn't actually change
    the image contents of the file.
    Take three identical photos and see for yourself!
    I'm quite confident is saying that "superfine" is compressed at least 3 or 4
    times smaller than an uncompressed (TIFF) image. Otherwise, there's not much
    point to using JPEG. It will likely look almost as good as TIFF (or RAW,
    presuming that you do all the sharpening, white-balance, etc. to it).

    On my camera, it's very difficult to tell the difference between the two
    JPEG compression levels. One is a 4x compression, while the other is an 11x
    compression. On another camera of mine, I begin to notice image degredation
    at its highest compression level which is 16x. So, you're probably safe
    shooting at compression levels around 10x or less.
    gr, Oct 17, 2003
  6. Gary Fritz

    VT Guest

    According to review of the Canon A70

    The estimated JPG compression ratios were:

    SuperFine 6:1
    Fine 10:1
    Normal 20:1

    One can work this out
    the image is at 2048x1536pixels and each pixel is 3-bytes - so that's
    2048*1536*3 bytes = 9,437,184 bytes.

    So at Canon's spec'd file sizes - the compressions are:
    SuperFine 1,602Kb => 5.9:1
    Fine 893Kb =>10.6:1
    Normal 445Kb =>21.2:1

    Many people find it very hard to see the difference between Fine and
    SuperFine - in fact I have some shots that appear as if the Fine had
    resolved more detail than the SuperFine - that could well have been an
    anomoly - but I did it more than once.......

    So do what you have already suggested, shot normally in Fine mode and
    when you do see a WoW! picture switch to SuperFine.......

    Although Compact Flash cards are pretty cheap these days -

    128Mb CF ~$30
    256Mb CF ~$50
    VT, Oct 18, 2003
  7. Gary Fritz

    Gary Fritz Guest

    Right. I should have been clearer. I wasn't looking for how much *file*
    size compression it does, but how much that affects the final picture.
    Hm. OK. And it sounds like I'm just going to have to do some test shots
    and get a feel for it myself. And switch to Superfine for those "WoW!"
    shots. :)

    Gary Fritz, Oct 20, 2003
  8. Gary Fritz

    VT Guest

    That's what you'll have to do anyway, right? :)

    Even if someone came out with some really convincing argument for or
    against Fine vs. SuperFine - one would probably want to do some tests
    to re-assure/confirm the results....... :)

    Just to give you a head start -
    I did that in a post, with detail photo samples - using a Canon A70 -

    SuperFine vs. Fine JPG

    Hope this helps.
    VT, Oct 20, 2003
  9. Gary Fritz

    Gary Fritz Guest

    Excellent! Thanks, Vincent. That helps. Even at 2x blowup I'm hard
    pressed to see any difference between the two images. That's on a monitor
    with about 100dpi (19" monitor, roughly 15" across, at 1600x1200). I would
    assume most pics would get printed at 200-300 dpi unless you cropped it a
    lot (like you did in your post). E.g. a full-frame 5x7 from a 3MP image
    would print at about 300dpi, an 8x10 at about 200dpi. So if I can't see
    the differences at 100dpi, it seems unlikely you'd see them at 200dpi.
    That's good to know.

    I can see definite differences in your "Enhanced" version, with increased
    sharpness in the needles, but that comes at the cost of some significant
    JPG artifacts at sudden bright-to-dark transitions.

    Gary Fritz, Oct 20, 2003
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