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Canon 5D III ISO 50 overexposure

Alberto
2012-07-13
2013-02-27
  • Alberto
    Alberto
    2012-07-13

    Hi all,
    I have just discovered that ufraw seems to overexpose by 1 stop the photos taken at ISO 50 on the 5D Mk III. Ufraw, instead, converts the same files correctly.

    Regards,
        Alberto

     
  • Alberto
    Alberto
    2012-07-13

    Obviously I meant that dcraw exposes the files correctly, sorry!

     
  • Beware that UFRaw does not use autocorrection of exposure while DCRaw does. You have to use the '-W' switch with DCRaw to compare the two programs. Does that make any difference?

    My guess is that base sensitivity for the 5D mk. III is ISO 100 and ISO 50 is one stop overexposed by the camera. The review at www.cameralabs.com seems to suggest that. That leads me to conclude that UFRaw is doing the right thing.

    Regards,
    Niels Kristian

     
  • Alberto
    Alberto
    2012-07-22

    Niels,
    you are correct: ISO50 is fake (ISO 100 overexposed) as well as ISO 25600, 51200, and 102400 (12800 underexposed and pushed in post).

    Ufraw with the -W option converts ISO 50 with the correct exposure, as ufraw does with ISO 12800 (I haven't tried the higher ISOs yet). I think that the behavior should be consistent with all "fake" ISOs and ufraw should convert all of them with the correct exposure as dcraw does.

    Regards,
       Alberto

     
  • Hi Alberto.

    Would it be possible for you to make an ISO 50 test image available for download or send one to me at nkbj(at)users.sourceforge.net using yousendit.com or a similar service? I will look into the problem then.

    Regards,
    Niels Kristian

     
  • Hi Alberto.

    Have you sent me a test file yet? I have tested UFRaw with the ISO 50 file from www.photographyblog.com and it shows no problems at all.

    Regards,
    Niels Kristian

     
  • Alberto
    Alberto
    2012-09-13

    Hi Niels,
    sorry, but for some unknown reasons I missed your reply. I sent the file by mail right after you asked. I will be resending it in a minute. I still have the problem with ISO 50 files. I will check the raw from photograpyblog ASAP.

    Regards,
       Alberto

     

  • Anonymous
    2012-11-25

    Hi Niels,

    I am unable to get anything but a washed out pic using ufraw on raw files from my EOS 5D Mark III; no amount of manipulation corrects it.  It is as if the brightness was cranked up to the max.  Using the camera WB, it gives a pinkish hue, but still washed out; auto WB gives light greeenish wahed out pic.

    I have verified that using Canon's utilities the pic has a normal appearance.

    With my 5D Mark II, ufraw worked well.

    Thanks,
    John

     
  • Alberto
    Alberto
    2012-11-25

    John,
    this is very strange. I have been using ufraw with my 5D III files for months and I have never had any of these problems.
    About ISO 50, I discovered the problem, but I forgot to post it here: ISO 50 is probably an overexposure by 1 stop of ISO 100, but the in-camera curves are not the same as for other ISO values to preserve dynamic range (as much as possible). Therefore, the contrast curve that I was using in ufraw was not correct with ISO 50.

    Regards,
       Alberto

     

  • Anonymous
    2012-12-01

    Alberto,
    Sorry i have been busy this week.  I am not sure what the problem is, but it occurs for all of the raw files of photos i have taken with my 5D-III.  This is true for a variety of ISO settings and stops.  I tried deleting the .ufrawrc, but the problem persists.  All of the raw files that i have looked at are fine in Canon's Digital Photo Professional Viewer.

    Are there any dependencies that are not explicitly indicated in the ufraw RPM package?  My distribution is SuSE 12.1.

    Thans,
    John

     
  • Alberto
    Alberto
    2012-12-15

    Hi John,
    sorry for the delay in getting back to you.
    What I believe is that you are using an old release of ufraw that do not support 5D III files. You should try using a snapshot from cvs. Unfortunately, there have been no official release for a long time and using the cvs is the only way to get updates…

    Best,
       Alberto