raw on Linux - pointers?

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Offline bugbear

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    raw on Linux - pointers?
    « on: 07 / May / 2008, 04:06:48 »
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    I'm just starting on the whole RAW thing; I want to do some post processing (probably in netpbm scripts).

    I've tried setting the software to RAW (Allbest on A630).

    I've struggled to do anything "useful" with the results.

    General question; I've read that the raw data is only 10 bit. Is this a limitation of CHDK or the camera?

    Even more newbie question; using both dcraw and UFraw the colours in my images look way off; I mean really, really bad and wrong.

    I assume I'm just missing the point entirely.

    I have looked for tutorials and intros, but failed to find anything useful.

    So - can anyone point me to a step-by-step (or some close approximation) or working with RAW files on Linux?

       BugBear

    (oh - my first procesing project is intended to be very long exposures, emulated via averaging of multiple 5-10 second raw exposures with single (i.e. common) dark frame subtraction)

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    Offline dazzy

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    Re: raw on Linux - pointers?
    « Reply #1 on: 07 / May / 2008, 10:24:20 »
    1. Canon digital compacts have only 10bit ADC. This is hardware limitation. CHDK alone can do nothing about it.

    2. It's said that color matrixs of CHDK RAWs in dcraw are quite wrong. UFRaw is no exception since it utilizes the same code to decode RAW. You can read the sticky thread "    
    New project: camera color profile calculation " for more information. The DNG4PS2 comes up as a handy tool for CHDK RAW process.

    Basic workflow: convert the CRW to dng via DNG4PS2, then use whatever raw editor with dng support to open those dngs. It's quite the same on Linux, Win32 and Mac OS.

    For advanced RAW editing, the FAQ and RAW section of CHDK wikia, and also talks on these articles are good places to dig.
    « Last Edit: 07 / May / 2008, 10:27:46 by dazzy »

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    Offline bugbear

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    Re: raw on Linux - pointers?
    « Reply #2 on: 09 / May / 2008, 09:56:56 »
    1. Canon digital compacts have only 10bit ADC. This is hardware limitation. CHDK alone can do nothing about it.

    OK, that's fine. I was looking to criticise, just wanted confirmation.

    Doh! (edit) "wasn't looking to criticise"

    Quote
    2. It's said that color matrixs of CHDK RAWs in dcraw are quite wrong. UFRaw is no exception since it utilizes the same code to decode RAW. You can read the sticky thread "    
    New project: camera color profile calculation " for more information. The DNG4PS2 comes up as a handy tool for CHDK RAW process.

    Basic workflow: convert the CRW to dng via DNG4PS2, then use whatever raw editor with dng support to open those dngs. It's quite the same on Linux, Win32 and Mac OS.

    For advanced RAW editing, the FAQ and RAW section of CHDK wikia, and also talks on these articles are good places to dig.

    ok, thanks for your help.

      BugBear
    « Last Edit: 12 / May / 2008, 07:02:52 by bugbear »

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    Offline BB

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    Re: raw on Linux - pointers?
    « Reply #3 on: 09 / May / 2008, 11:28:25 »
    While I am an absolute beginner if digital photo editing--and have zero artistic sense--I have found that I could pull sky highlights very easily out of the RAW photo vs the camera JPEG.

    From what I have seen, if you like the JPEG's out of the canon cameras and don't need post processing--you will find it very difficult to improve on what comes out of the camera (with a little tweaking of camera defaults, possibly pull EV to -1/3, use vivid colors in a bland environment, use neutral or custom colors with saturation dialed down in a colorful environment ,or if you want to post process, use custom and dial back the sharpening, etc.).

    Besides the somewhat expanded dynamic range (highlights and shadows that, in RAW, are not simply white or black), RAW is good for where you will be doing a lot of post processing. Things like WB correction, pasting, croping, etc. are better done on the original data than JPEG that has already been adjusted (by the camera) for screen/print display.

    For example, sharpening on a JPEG cannot easily be undone and if further processed can create halos and false colors on edges and fine lines (or further emphasize the halos, JPEG compression artifacts, and false colors already present in the original JPEG). Sharpening, as understand, should be done as one of the last steps--not the first step as would happen if a JPEG is post processed.

    -Bill


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    Re: raw on Linux - pointers?
    « Reply #4 on: 24 / May / 2008, 09:55:34 »
    So - can anyone point me to a step-by-step (or some close approximation) or working with RAW files on Linux?

    Hey bugbear,  I just started looking into RAW data on linux as well.  Check out the following programs:

    RawStudio - available in gentoo as well as others on their site
    RawTherapee - available for ubuntu as well as glib2.4 and glib2.2 systems from their site.

    Both of these will use the CRW file directly.  RawStudio even has an export to Gimp so you don't have to save in between.  You still have to guess at the WB but they make working with the RAW data much much easier!

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    Offline Aged

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    Re: raw on Linux - pointers?
    « Reply #5 on: 24 / May / 2008, 10:22:50 »
    Check out DCRAW it is the common base for many Raw readers.

     

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