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Thread: Editing 16-bit scans in RGB mode

  1. #1

    Join Date
    Jun 2018

    Editing 16-bit scans in RGB mode

    I just noticed that when I edit a 16-bit scan in photoshop, gradients tend to lead to posterization, especially with heavy transitions in areas with no texture (sky or water, with long exposure), to the point that they are not usable.

    By changing the mode to RGB, gradients become very smooth and everything works fine.

    I'm not sure why that is the case, as the image file is the same.

  2. #2
    Peter De Smidt's Avatar
    Join Date
    Jan 2001
    Fond du Lac, WI, USA

    Re: Editing 16-bit scans in RGB mode

    It might just be posterization on the monitor due to the display system having only 8 (or 10) bits per channel.
    “You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
    ― Alexander Den Heijer, Nothing you don't already know

  3. #3

    Re: Editing 16-bit scans in RGB mode

    You say "by changing to RGB mode". What color mode were you in and what is the original source of your scans. Are you talking about gradients within the image itself or about gradient masks, which will often band because they are in 8 bit no matter what that the overall file is. But it's more likely your monitor. If you don't have a "smart" monitor - one that does its calibration on high bit internal data, then whatever monitor calibration corrections are held in your video card lookup tables (LUTS) will bring the effective bit depth down to seven or even six, showing posterization on screen where it doesn't exist on the file.

    After you flatten your file and view it at 100 percent in Ps, does it still show the banding, both looking at the composite RGB channel and at the individual red, blue and green channels - obviously with those set to view as the Grayscale channels they really are. And don't forget that your Grayscale setup does affect how your red, blue and green and any alpha channels view in Ps.

  4. #4
    Steven Ruttenberg's Avatar
    Join Date
    Sep 2017
    Mesa, AZ

    Re: Editing 16-bit scans in RGB mode

    I notice that when working on a file that is at some small percentage of the full size file, like 10%. When I zoom to full size it goes away. It also does not present itself when I print.

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