Correcting Exposure and Adding Contrast in LAB

LAB color mode in often in lack of a better word underused. I often convert photographs (temporarily, of course) to LAB color mode to do all sorts of effects. Recently I was working on a batch of JPEG files because (unfortunately or fortunately) I didn’t have the RAW originals, so I needed to fix the white balance, exposure and contrast before any other manipulations. In this article I will explain how to fix exposure and add contrast using LAB color mode, and what are the benefits of this over RGB mode. I did this in Photoshop CS5, but I guess older versions should work the same, and even other programs which support Curves and LAB color mode should work.

If you are in RGB color mode and you wish to use either the Curves adjustment tool or the Levels adjustment tool (at least I usually do) to fix the exposure and while you’re at it add some contrast to the photograph. Alternately, you can use the Exposure adjustment (which is fine), but I prefer to use the LAB Curves for a couple of reasons:

  • fixes the exposure in a couple of clicks
  • enables you to modify the contrast as you go
  • doesn’t mess up the color balance as RGB curves or Levels do

Click on the buttons below to see the difference between:

  • before anything
  • after applying the curve on Lightness channel in LAB mode
  • after applying the same curve on RGB channel in RGB mode

How to do it? Follow the next few steps and you’ll be there in a second:

  1. Image / Mode / Lab Color – change the mode to LAB.
  2. Image / Adjustment / Curves – and configure the curves to your needs for exposure and contrast.
    1. Slide the upper-right corner left or right to increase or decrease lightness.
    2. Play with the Curve to set contrast as you wish, usually an S curve works well, but this really depends on the image.
  3. Image / Mode / RGB Color – change the mode back to RGB.

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