| Jack, it all depends on the image.
A simple fix is minor desaturation, which will add cyan to the overly magenta/yellow skintone (as cyan is the contaminating ink in the hue of red which adds detail and desaturates). This can be done with the sponge tool, adjustment layers etc.
At first blush it would seem that the Green or Magenta channels or the A channel in LAB are the first place to attempt to fix things if one is going to look into targeted channel based corrections.
I like channel mixer or apply image moves in Photoshop for tougher subjects, often using a mask which is based off the red/cyan and or K channels. The idea being to use the blue/yellow channel to lighten the green/magenta channel (but one must be careful as artifacts are often found in the blue/yellow channel and blending this data into a channel with more visual impact could create later retouching issues).
For a nice tanned caucasian skintone, the basic ratio of colour is a higher magenta value with yellow a bit higher and with the critical cyan value around 1/3 to 1/2 the magenta value ratio...say 17c 40m 50y (or in sRGB 211r 159g 129b).
The magenta/yellow describe the basic hue, which is red - while the balance of cyan desaturates the red so that it has some grey component to it, while cyan also builds the detail and shading.
This should not be a major problem to fix in most cases.
Hope this helps,
Stephen Marsh. |