Skin Color by the Numbers

March 28, 2013  •  Leave a Comment

Recently, one of my blog readers pointed out that the skin tone in a basketball action picture was too pink. Since Photoshop provides an objective way of measuring the skin tone, I thought this process would make for an interesting post! Here is the photo is question:

OYA girls' basketball To measure (and correct) for any color issues with the skin, I first open the file in Photoshop. I then open the "Info" palette (Window>>Info). Once the Info palette is open, select the "Color Sampler Tool". Then, drop a color sampler control point or two on representative portions of the skin on the face. Note the Color Sampler point #1 on her face:

Next, convert the RGB values inside of the Info palette to CMYK percentages by clicking on the little eyedropper on the left side of the readings. The readings should for the selected sample should now appear as CMYK percentage values. For this control point, the cyan reading is 13, while the magenta reading is 50:

Before proceeding, I refer to a few guidelines for reading an average caucasian's skin tone:

  • Take a reading of the cyan value. Magenta should be about double the value of cyan.
  • Yellow should be about 1/3rd to 1/5th higher than magenta.
  • Yellow and magenta should be about equal for babies and young people.

In the above photograph, the magenta value is too high as compared to the cyan readings. So, my reader is correct--the skin is too pink! My next step is to make some adjustments to the color curves to correct the skin tones. Before getting started with those adjustments, I create a Curves adjustment layer. I then select the Red channel within Curves:

Then, I select the portion of the curve that represents my first control point and drag the curve down (less red, more cyan) until the cyan reading increases to a more reasonable this case I stopped at 23. Why did I stop at 23? For one thing, I noticed that at the 23 level, the magenta reading (47) is about twice that of cyan.

Next, I make an adjustment to the same portion of the curve, but this time I open the Blue channel and drag it down (less blue, more yellow) until the yellow reading is a little higher than the magenta value. Since this is a young girl in the picture, I did not raise the yellow very far above the magenta level.

The skin color, at least for this portion of her face, looks accurate to me. And, the numbers bear that out. If you are not yet satisfied, you can always drop more Color Sampler points on different portions of the skin and use the same method for correcting each area. Also, if you don't like what's happening to the color of the background, feel free to mask it off in the layer.

OYA girls' basketball

I've used this method quite often when skin tones need correcting. Once you get the hang of it, you can accomplish the steps quite quickly.


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