Why RAW+JPEG on Canon 10D?

Discussion in 'Digital Photography' started by cc, Jan 10, 2004.

  1. cc

    cc Guest

    I have now read my 10D manual from cover to cover so I know what all the
    buttons are for. One thing (but not the only thing) that perplexes me is
    why there is an option to store a RAW+JPEG file, which is a RAW file
    with a JPEG embedded in it. To access the JPEG some special software is
    required, so I assume that means it can't be printed directly anyway,
    and the RAW file can easily be converted into a JPEG with a computer if
    a person really needs both formats. So why would someone waste space on
    their CF card to store an additional JPEG in their RAW picture? What can
    you do with a RAW+JPEG that you can't do with just RAW? Thanks?
    cc, Jan 10, 2004
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    Nils Rostedt Guest

    Actually it's the other way round. Viewers like Irfanview can read the
    embedded JPEG directly, which is nice for a first browse-through, or to
    print a draft 4x6, or to make a contact sheet of the folder.

    (I guess that RAW converters like FVU or BB actually also use the embedded
    JPEG for first display of the shot).

    Conversion tends to take time, for me it's about 24 sec for each RAW,
    whereas he embedded JPEG can be extracted in 1 sec to a separate JPEG file.

    So why would someone waste space on
    As outlined above - quick looks in a convenient full-screen format (about
    1500*1000) ; contact sheets; and quick-print 4x6s.
    After the best shots are identified, it's time to start working with RAW.
    Nils Rostedt, Jan 10, 2004
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    JPS Guest

    In message <>,
    The 10D's .crw (RAW) files are actually JPEGs, with the RAW data
    embedded within them (although you will often people speak of embedded
    JPEGs, the opposite is actually the case). They have a .crw extension
    instead of .jpg. Any program that looks into the file to see what it is
    will display the JPEG, and any that doesn't can be fooled by renaming
    the .crw to .jpg.
    JPS, Jan 10, 2004
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    JPS Guest

    In message <btpbpg$9uoid$-berlin.de>,
    The .crw file is actually a JPEG file. It is the RAW data that is
    JPS, Jan 10, 2004
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    Jim Townsend Guest

    If you look in the English Canon 10D manual at the custom function
    section (page 148)... C.Fn-08 is explained:

    "Sets the recording quality of the JPEG image recorded simultaneously
    and embedded in the RAW image file".

    Canon mentions a RAW image and indicates the JPEG image is "embedded
    in the RAW image file".

    Where did you hear the RAW file is a JPEG with RAW data embedded ??
    Jim Townsend, Jan 10, 2004
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    JPS Guest

    In message <>,
    I don't wait until I hear things. I conduct experiments. Every
    graphics program that I tried has been able to load the CRW file as a

    Go ahead - try it. Make a duplicate of a .crw file, and then copy it
    also with a ".jpg" extension. The ".jpg" will open in almost any
    program that reads JPEGs. In some, you don't even have to rename it.
    JPS, Jan 10, 2004
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    Jim Townsend Guest

    That's specious reasoning.. You can't claim a RAW file is a JPEG
    file because some image editors are capable of extracting the JPEG
    info from within the file.

    I have a program that extracts EXIF info from JPEG files and
    produces a text file. But because of that, I can't claim JPEG
    files are text files with image information embedded within.

    Is it not possible that Canon designed its RAW files to 'hand over'
    the embedded JPEG info when certain editors tried to open them ?

    All it would take would be to put a pointer or shortcut in the
    RAW file header that pointed to the location of the embedded JPEG

    That way a JPEG editor would open the file, see the pointer and
    happily go to the JPEG data and load it.
    FWIW, Adobe Photoshop Elements won't read a RAW whether you rename it
    or not.

    PS.. I'm not saying you're wrong.. I just need more to convince me :)
    Jim Townsend, Jan 10, 2004
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    cc Guest

    When I set it to save just a RAW without a JPEG it still saves it as a
    ..crw file. Is this file also a JPEG and can it be opened like a JPEG? I
    see some thumbnail files saved with the RAW files and I assumed these
    are what were used for the previews. The .crw files take much longer to
    download from the camera.
    cc, Jan 10, 2004
  9. See if I can convince you that JPS is right :)

    JPEG is not a file format, it is a compression method and format.

    RAW is not a file format, it is a data representation format.

    The file format used by Canon for storing JPEG and for staring
    RAW files is called JFIF. Here is a link that givs the details:


    Roland Karlsson, Jan 10, 2004
  10. cc

    Jim Townsend Guest

    Roland Karlsson wrote:

    Why will Adobe Photoshop Elements recognize a Canon JPEG, but
    not a Canon RAW file ?

    If they are both JFIF, why is one recognized and the other not ?
    Jim Townsend, Jan 10, 2004
  11. When I set it to save just a RAW without a JPEG it still saves it as a
    How do you pull off that trick? There is no option for RAW without JPG.
    Randall Ainsworth, Jan 10, 2004
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    Jim Townsend Guest

    You can't save in RAW without a JPEG embedded. Both the 10D and 300D
    do this automatically.. There is no way to turn it off.
    Jim Townsend, Jan 10, 2004
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    cc Guest

    Ahh ok there is an option for what size and compression the JPEG is, not
    to remove the JPEG altogether. I guess I was reading the manual too late
    at night and I forgot that. So I guess my original question is kinda
    cc, Jan 10, 2004
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    Cello Guest

    According to Canon literature, the real reason is that the small jpeg image
    allows the user to see the image on the viewfinder instantly. Otherwise,
    they would have to have firmware or software in the camera to convert the
    raw data before it could display on the screen.

    Its a "the user wants it now" fix.
    Cello, Jan 10, 2004
  15. cc

    Chris Brown Guest

    This would appear to be incorrect. Both commonly used types of JPEG file
    (JFIF and EXIF) identify themselves with the string, "JFIF" or "EXIF" near
    the start of the file (8th byte?). CRW files do not have this identifying
    Chris Brown, Jan 11, 2004
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    Hans Kruse Guest

    That's not true at all. Try to open it with Microsoft Photo Editor. It won't
    Hans Kruse, Jan 11, 2004
  17. CRW files are definitely not JPEGs. The OP may be getting confused by the
    fact that when you shoot RAW, each shot produces a CRW file and a THM
    file. The THM file is just a renamed JPEG image. The CRW file is a Canon
    proprietary format (CIFF based) which embeds a larger JPEG image. On most
    Canon cameras, the larger JPEG is of a fixed size, but on the 10D, the
    size can be selected with a custom function.

    This is actually quite useful - you can shoot in RAW+large/fine JPEG
    exclusively, but have a small shell script/batch file that extracts the
    embedded JPEG, copies the EXIF data from the THM file into it, and then
    rotates any images in need of rotation. This gives you a very fast
    workflow, and if you want to go back and tweak any shots in a real raw
    converter, you can. It costs on disk space, but some programs (new
    versions of BreezeBrowser, for example, can regenerate the embedded JPEG,
    so you can reclaim the space later.

    Mike Brodbelt, Jan 11, 2004
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    JPS Guest

    In message <>,
    You can't set the 10D to save a RAW wthout a JPEG. RAW mode always
    includes two JPEGs; one inside the same file as the RAW data, and one in
    a tiny JPEG with a .thm extension.

    The review function in the camera uses both; it uses the .thm for the
    initial view, and when you see it sharpen up, suddenly, it has read the
    larger JPEG from the .crw file.
    JPS, Jan 11, 2004
  19. cc

    JPS Guest

    In message <>,
    JPS, Jan 11, 2004
  20. cc

    Chris Brown Guest

    Chris Brown, Jan 11, 2004
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