Pentax K10d

Discussion in 'Pentax' started by frederick, Sep 13, 2006.

  1. frederick

    Paul Mitchum Guest

    The brochure says that the *converter* has that much greater dynamic
    range, and that's a true statement, all things being equal. The trick is
    how you get from 22-bpc to 12-bpc for RAW, or 8-bpc for JPEG.
    Paul Mitchum, Sep 16, 2006
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  2. Well, I won't disagree, it just seems to me a more important reason
    (DR, that is). But as I said, I have no clue anyway.

    As for compression, you really should listen to Classic FM next time
    you're in London. They compress classical music like it's rock.
    But think about it: If I shoot the exact same scene twice, with the
    same aperture setting and shutter speed but ISO 100 and then ISO 1600,
    then in one photo I'll get lots of detail in the shadows, in the other,
    in the highlights (I assume a scene exceeding the recordable DR at a
    given single ISO). Since the amount of light reaching the sensor is the
    same, and the sensor's output I assume to be the same (before
    amplification), I conclude that the reason we do not record the full DR
    is related to the A/D conversion. That is, the information is lost
    during the digitisation. More bits would allow us to keep this.

    Of course, when converting to 12 bits we may lose some, but this may be
    avoided by applying a nonlinear conversion curve, just like you
    describe below. If Pentax was doing this, I'd think they'd have made a
    lot more noise about it. But we'll see.
    Yes, once it was digitised to 22 bits (or whatever number), it could be
    examined and a nonlinear curve to map it to something representable by
    12 bits could be calculated. This could also be stored in the raw file
    for use by the converter (otherwise, how could it know which curve was
    used?). As I said, I doubt this is done in this camera. And anyway, it
    would require different postprocessing techniques (like people do with
    HDR images).
    No, I meant that I don't think posterisation will be reduced, unless
    some kind of nonlinear curve was applied (and this would need to be
    stored with the raw data; just like Nikon does with its compressed raw
    format, which basically uses a two-piece curve to map the data to a
    smaller number of bits than 12; this curve is stored in the raw file,
    although I think it's always the same). Rather too revolutionary to
    keep quiet about.
    Sure it does, see above (same exposure, different ISOs example).
    Yes, I agree. It's what people do with HDR images, which have a high
    bit depth and must be reduced to be saved as eg 16 bit TIFFs. This is
    done in Photoshop by adjusting gamma (I think there's nothing else you
    can adjust there, but of course in principle one could have any
    arbitrary mapping curve).
    No disagreement that this could be done. I just don't think it is in
    this camera!

    achilleaslazarides, Sep 17, 2006
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  3. frederick

    John Francis Guest

    This is precisely what some people are interpreting the (rather
    imprecise and ambiguous) description in the Pentax press release
    to mean. I know of a few people who have received rather more
    detailed information from Pentax, and who are eagerly awaiting
    a chance to see real images from a production K10D.
    John Francis, Sep 17, 2006
  4. frederick

    acl Guest

    That's interesting. Let's see.
    acl, Sep 17, 2006
  5. No, I meant that I don't think posterisation will be reduced, unless
    Actually, you could till get *some* improvement withut resorting to
    this, simply by applying some intelligent "unsharpening" to areas that
    appear as if they will end up posterized. Whether or not this feature
    is there or not, I can't either. All I can say is there must be *some*
    reason they are using the 22-bit processor and bragging about it, and
    these seem plausible.

    Marc Sabatella

    Music, art, & educational materials
    Featuring "A Jazz Improvisation Primer"
    Marc Sabatella, Sep 17, 2006
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