Sony In-Camera-Gamma-Adjustment Can Change RAW

Discussion in 'Sony Cameras' started by VidThreeNorth, Mar 13, 2019.

  1. VidThreeNorth

    VidThreeNorth No longer a newbie, moving up!

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    Here is something that you can probably ignore for the rest of your life, or it might affect your camera usage tomorrow. Apparently, changing the "Gamma" in "Picture Profiles" CAN change your RAW file. This might prove a useful way to optimize the use of your camera, or it might be something you will want to avoid. At this point, I don't know which. But at the least, it is good to be aware of it:

    "YES, Sony Picture Profiles DO Change Raw Photos!", posted Mar 2, 2019 by "Gerald Undone"



     
  2. Ysarex

    Ysarex Been spending a lot of time on here!

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    His methodology is suspect. You don't look to see the condition of a raw file by loading it into a raw converter, especially not LR. Also suspect would be that he changes his premise from the beginning of the video to the end. Just after 1:00 minute his premise is: "but they do, they definitely do" picture profiles change the raw files which is likewise noted in the video title. Then at 9:00 minutes his premise has become, "Changing the gamma changes the way the raw is developed." That is in fact an entirely different claim and very possibly an entirely different process. Does changing the gamma in picture profiles cause a Sony camera to write a different raw file? There's really no answer to that question in the above video.

    Joe
     
  3. VidThreeNorth

    VidThreeNorth No longer a newbie, moving up!

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    You're right about the discrepancy between what he says at the start of the video and the end. I think he realized that he did not know if the difference was the contained image data or just a "header parameter". More investigation needs to be done.

    Still, it is an important issue and I appreciate the report even with its shortcomings. He has definitely "found something", and because it contradicts what he had said before, it was a good idea to post at least this much for now -- pointing out that there is "something going on" that might affect camera usage. I see it as "acting responsibly" rather than ignoring an error he made in the past, or even "putting off the report" till he understood it more completely.

    Beyond that, is the question of which models does this affect? I checked my (bottom of the line) a5000 and it does not have this capability.

    What about other brands of cameras? Does something similar happen with Nikon, etc?
     
  4. Ysarex

    Ysarex Been spending a lot of time on here!

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    That's right and I think he started to change his language because he was starting to suspect it could just be a flag in the header. And he went on to say if so that doesn't matter but it does, flags in the header don't change the underlying raw data. I don't know about this case. I have a Sony camera at work but not at home so I'm not going to pursue it. Other cameras definitely place flags in their raw file headers that LR and C1 honor -- my Fuji does. That's why you can't do a test like this with LR. This is what Raw Digger is for.

    If in the past he went public claiming the profiles had no effect on the raw files and now he's making a correction that's good -- as you say "acting responsibly." Now he needs to get a little more competent. I've encountered him previously as my students get info off Youtube and bring it to me. Unfortunately I've encountered him spreading error.

    Joe

     
  5. VidThreeNorth

    VidThreeNorth No longer a newbie, moving up!

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    I have been following the "Comments" for the video and I think that the discussion has clarified the situation.

    First the short answer is that yes, changing the Gamma itself and nothing more will "change" the content of the raw. But it is not as significant as it sounds. The change is no more that what results from changing the ISO appropriately.

    The short description of what is happening and why is like this:

    First, the changes to the Gamma are limited to applying the Gamma from some of the available VIDEO profiles in the cameras. That is to say for example, you set and use the Gamma from the "Slog2" video profile for still pictures. If you do that, then the camera "re-scales" the ISO to give appropriate exposure to your picture.

    So when you nominally set ISO 2000 in under "Slog2", the camera is acting as if you set a different ISO under the normal Gamma. It also probably sets parameters to tell a processing program how to handle the image data, but the resulting image data in the raw file will only reflect the change in the exposure.

    Possible Justifications:

    The question of why this "capability" is provided has a sound theoretical base. There are two ways that a photographer who is involved with video production might find this useful. First, if you are "scouting" then taking the pictures with the camera set up like a video camera can help predict how the
    final video recording will look when it is all processed. It might also help provide guidance notes to the camera crew and anyone doing post processing.

    The second possible advantage is that if you take still pictures that might be included in the final production, the "look" and the processing could better match the rest of the video in which they are incorporated.

    Is it "a big deal?"

    Probably not that much.

    At the front end of the production cycle, scouting shots do not really have to resemble final production that much. I cannot say more than that because different producers, directors, etc. will have their own point of view on the matter.

    As far as "included" stills are concerned, editing software can generally treat all the "objects" (video clips or still images) individually. So a still image is processed with its own adjustments which will not have anything to do with the previous video clip object or the following object.

    Outside of Video Productions

    In the case of someone just interest in taking still pictures outside of any "video production" situation, one might as well just ignore this stuff. It will not help you get better pictures.

    See:

    'PXW-FS5 Official Tutorial Video #1 "Picture Profiles" | Sony Professional', Published May 29, 2016, "Sony | Camera Channel",
    ""

    Also See:
    "Why are Sony’s ISO’s different between standard gammas and log?," by alisterchapman, published September 10, 2017, XDCAM-USER.COM
    "Why are Sony's ISO's different between standard gammas and log? | XDCAM-USER.COM"
     

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