Looking for technical info about Raw files

Discussion in 'Digital Cameras' started by LSE, Jul 16, 2003.

  1. LSE

    LSE Guest

    Hello,

    I'm lloking for a url about what is exactly a raw file and what does
    the processing really do.

    This request because I don't understand how a third part software can
    process a raw file (more exactly how does the third part software with
    color each value represents).
    Which information does exactly a Raw file contain and so on ?

    Thanks in advance

    Luc
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    LSE, Jul 16, 2003
    #1
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  2. A raw file contains lots of bits of information. It contains a lot of
    settings data (like EXIF, but more detail) about focus, focal length,
    exposure, aperture, lens, date/time, white balance, etc etc. It also
    contains an embedded JPEG image, and a losslessly compressed dump of the
    raw sensor data from the CMOS chip.
    RAW files are CIFF format, and the CIFF contains multiple hierarchical
    heaps. Heaps contain records (or subordinate heaps). A good (though
    somewhat dated) reference to the type codes can be found at
    http://www.wonderland.org/crw. An open source reference decoder for RAW
    files can be found at http://www2.primushost.com/~dcoffin/powershot/.
    David Coffin's dcraw.c will do the image demosaicking, and output a PPM
    file. You can also get parse.c, which will parse the CIFF heap structure,
    and extract the embedded JPEG. On the 10D (but not on the previous Canon
    DSLRs, the size of the embedded JPEG can be set to any resolution the
    camera is capable of.

    To understand the CIFF structure, look at parse.c. To understand the
    processing required to create an image, look at the reference
    decompressor. To learn more about the theory behind bayer array
    demosaicking, look at http://www4.ncsu.edu:8030/~rramana/research.html

    HTH,

    Mike.



    HTH,

    Mike.
     
    Mike Brodbelt, Jul 16, 2003
    #2
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  3. LSE

    LSE Guest

    Whaooo this is what I call an answer !!

    Thanks a lot mike

    [...]
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    LSE, Jul 16, 2003
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