Converting RAW to TIFF Question

Discussion in 'Digital Photography' started by Jason, Mar 7, 2006.

  1. Jason

    Jason Guest

    Why is it that when you convert a RAW image to a TIFF the image size
    dramatically increases?

    Where does the extra info/file size come from, because obviously the RAW
    image is the original?
     
    Jason, Mar 7, 2006
    #1
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  2. Jason

    rafe b Guest

    "Jason" <> wrote in message
    news:...
    > Why is it that when you convert a RAW image to a TIFF the image size
    > dramatically increases?
    >
    > Where does the extra info/file size come from, because obviously the RAW
    > image is the original?



    Because digcam specs lie, but we live with the lie.
    As lies go, this one's not the worst. Not like phony
    WMDs, for example.

    A so-called "6 megapixel" DSLR or digicam really
    has 6 million sensors, of which 3 million are green,
    1.5 million are red, and 1.5 million are blue. Look
    up "Bayer Pattern." From these six million sensors,
    software (in the RAW converter) creates six million
    RGB pixels.

    The other (and smaller) part of the "magic" is simple
    lossless compression.


    rafe b
    www.terrapinphoto.com
     
    rafe b, Mar 7, 2006
    #2
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  3. Jason

    Jim Townsend Guest

    Jason wrote:

    > Why is it that when you convert a RAW image to a TIFF the image size
    > dramatically increases?
    >
    > Where does the extra info/file size come from, because obviously the RAW
    > image is the original?


    Most RAW formats use lossless compression which reduces the size.
     
    Jim Townsend, Mar 7, 2006
    #3
  4. Jason

    John Bean Guest

    On Tue, 7 Mar 2006 20:48:26 -0000, "Jason" <>
    wrote:

    >Why is it that when you convert a RAW image to a TIFF the image size
    >dramatically increases?


    No, the *file* size increases. Not the same thing at all.

    >
    >Where does the extra info/file size come from, because obviously the RAW
    >image is the original?


    There is no more (real) information, usually rather less.
    TIFF isn't a particularly efficient format, it uses a lot of
    file space to store the image.

    --
    John Bean
     
    John Bean, Mar 7, 2006
    #4
  5. Jason

    werdan Guest

    "John Bean" <> wrote in message
    news:...
    > On Tue, 7 Mar 2006 20:48:26 -0000, "Jason" <>
    > wrote:
    >
    >>Why is it that when you convert a RAW image to a TIFF the image size
    >>dramatically increases?

    >
    > No, the *file* size increases. Not the same thing at all.
    >
    >>
    >>Where does the extra info/file size come from, because obviously the RAW
    >>image is the original?

    >
    > There is no more (real) information, usually rather less.
    > TIFF isn't a particularly efficient format, it uses a lot of
    > file space to store the image.
    >


    Also cameras generally shoot 12bit colour which generally gets 'padded' out 16bit when converted to
    TIFF (although you can go back to 8bit as well)
     
    werdan, Mar 8, 2006
    #5
  6. "Jason" <> writes:
    > Why is it that when you convert a RAW image to a TIFF the image size
    > dramatically increases?


    Because of Bayer interpolation.

    The RAW file out of camera typically contains data from a number of
    monochrome photosites, 50% are green, 25% are red and 25% are green.
    When RAW is converted to TIFF, the 12 bit data from a single
    monochrome photosites are converted into a 24 bit or 48 bit
    full colour (RGB) pixel.

    > Where does the extra info/file size come from, because obviously the
    > RAW image is the original?


    The "extra" data comes from the neighbouring photosites.

    There is of course no extra information in this - but the RGB image
    that results from this process is suited for human viewing. The RAW
    image is not.
    --
    - gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
    ------------------------------------------------------------------------
    SD10, Kodak DCS460, Canon Powershot G5, Olympus 2020Z
    ------------------------------------------------------------------------
     
    Gisle Hannemyr, Mar 8, 2006
    #6
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