Have you every taken a set of images where the skin tone just does not look right to you? Your white balance could be off for a number of reasons including improper camera settings or mixed lighting (strobe/daylight/colored gels). Ok, so you forgot your color checker, or did not perform a custom white balance, it happens to almost everyone. The question is though... is the appearance of the skin really off? Is your monitor calibrated? Are you trying to edit at 3 a.m. in the morning?
Checking your monitor calibration with one of the tools such as the Datacolor Spyder or Colormunki is always a good idea, especially if you print images on a regular basis. There is great info on both products within the links that I have provided above. Lets assume though that your have already have performed your monthly monitor calibration.
Within Photoshop, you can gain some quick as important info using the eye dropper tool. The steps are pretty easy.
In almost every case, the %yellow should not fall below the % magenta. Most Caucasian skin will fall 5-20% more yellow than magenta. The more bronze the skin (as tanned) the person may be, the higher yellow and magenta will be in terms of percentage. For example, A fair skinned Caucasian may have 25% yellow and 20% magenta, whereas a very tanned person may have 62% yellow and 45% magenta.
The same technique may be applied to looking at skin tones in other cultures. African-American skin tones are fairly close together when looking at the yellow-magenta percentages. Asian and Hispanic skin will typically have 10-20% more yellow than magenta.
Well, what can you do about it?
As with most operations in Photoshop, there are of course other options. As you might imagine though this can get rather tedious particularly if you have shot hundreds or even thousands of images. A good rule of thumb is to be sure to take a good look at what lighting conditions are (or might be) around you and make appropriate adjustments while you are shooting.
-Bob Barford is a published photographer is Southern PA.