4 Replies Latest reply on Jun 4, 2008 2:16 PM by Ramón G Castañeda

    Trying to understand auto adjustment

      Hello, I'm using CS2 and some time ago I read (I don't recall where) that one should generally start at the top of the adjustment panel and work down when adjusting a RAW file: i.e. start with Temperature then do Tint; do Exposure before Shadows and before Brightness. Sure one might have to go back to adjust one of the higher ones... but that's part of the skill in using it. This rather made sense, trying to be systematic about adjustment.

      I recently was playing with a shot from a Canon camera that was underexposed and dark. I increased Exposure by nearly stop but it was still a bit dark. I took the shadows down and increased brightness a bit. I reduced contrast somewhat. It didn't look right.

      I hit "Auto" and it was a reasonable approximation. Certainly no worse than I had done. But I was confused to see that Exposure had been reduced by over a stop (when it was underexposed in the first place) and then brightness was increased.

      For example:
      Exposure Shadows Brightness Contrast Saturation
      Image settings 0 5 +50 +25 0
      My attempt +0.8 2 +82 -17 0
      Auto -1.2 1 +103 0 0

      I can't work out why it would reduce exposure so much but then increase brightness a lot. They're bigger adjustments than I made.

      Can anyone point me at something that explains how to adjust properly and/or what the "auto" setting does so that I can improve my RAW processing of darker images?

      Thanks.
        • 1. Re: Trying to understand auto adjustment
          Level 1
          Exposure is the white point clipping and the Blacks is the black point. Auto looks at the histogram and tries to do an optimal distribution of levels while trying to avoid clipping useful whites and blacks. In general, the better tool for adjusting the overall lightness of an image is Brightness not exposure.

          Depending on the scene and the camera exposure, there may be clipped highlights even in what looks to be a dark image. That's what the Brightness slider is for...adjusting the midpoint of an image.
          • 2. Re: Trying to understand auto adjustment
            MadManChan2000 Adobe Employee
            Also, sometimes you may need to work iteratively. It's not a bad idea to start at the top and work your way down, but sometimes it is helpful to go back to the top and make slight tweaks (i.e., revisit your initial adjustments).
            • 3. Re: Trying to understand auto adjustment
              Level 1
              Jeff, now that you say it I remember that exposure/shadow are white/black. :( I think I get confused because the word "exposure" rather means what I exposed and it shows "stops" of adjustment - in other words it sounds like it does what the brightness really does.

              ACR is the tool I use because I have it, but I have to say I'd use something else if it looked good!!

              Eric, I do tend to work iteratively. It was just that this is clearly not how Auto worked and it confused me considerably. With my new (renewed) understanding I'm looking at my images in a different light and have already improved what I've been doing before.

              Thanks both for your responses.
              Mark
              • 4. Re: Trying to understand auto adjustment
                Ramón G Castañeda Level 4
                Mark,
                >"exposure" rather means what I exposed and it shows "stops" of adjustment - in other words it sounds like it does what the brightness really does.

                Read Jeff's post again.

                what the Brightness slider is for...adjusting the midpoint of an image.


                Watch what happens to the histogram as you increase Exposure as opposed to when you increase the Brightness slider.