Skin tones "by the numbers" and a curves guide...
That's Bruce Beard's Skintones Color chart. He also has one for hair color. It's a great "retoucher's" resource. And one can NEVER have too much information and resources. Thanks for posting that one
klynam wrote in post #6570567
Just as I learned to use the histogram to accurately judge exposure instand of the image preview, I'm beginning to explore skin tones "by the numbers" rather than solely trusting my visual perception through capture > post > printing.Does anyone have or know of a reference with specific (RGB,LAB,CMYK) equivelancy values for ALL skin tones?
Skin tones "by the numbers" for me, doesn't mean exact numbers. The range is far too wide. Bruce Beard's chart is a good reference for hand-coloring images and traditional retouching. But Dan Margulis, before he wrote the LAB technique so many use to punch up colors, wrote a great book on color correction by-the-numbers, "Professional Photoshop: The Classic Guide to Color Correction" that has some general guidelines on skin color.
You'll also find his numbers used on SmugMug's guide to skin color.
Here's a quick and dirty guide to color correction, Margulis style, that may help. This is a general guide covering a range of skin tones. Treat them as ratios, not numbers carved in stone.:
For Caucasian skin:
- yellow should be equal to or up to + 1/3 of the magenta - cyan should be 1/5 to 1/3 less than magenta (the more bronzed the skin, the higher the cyan percentage)
Hispanic and Asian:
- yellow is higher than magenta
- cyan is 1/4 magenta up to +1/3 magenta
A wide range. Lighter skin tones are similar to Hispanic/Asian. For darker skin tones, yellow and magenta can be equal. Cyan, there is no limit.
How to Measure Skin Color
These numbers are measured using the color sampler tool, which is found grouped with the eyedropper in the tools palette. Make sure the "Sample size" on the options bar is set to a number appropriate to the image resolution. Try 5x5 to start. Click on the image to set the samplers on areas of the face which are typical skin colors on evenly lit areas of the face, not in highlights or shadow.
Then open the info palette (Window>Info). You'll find your sampler numbers listed at the bottom, #1-4. Next to each set is an eyedropper. Click on the very small arrowhead to open up the menu and choose "CMYK". You don't have to convert your image to CMYK, these numbers just make the adjustments easier.
Adjusting Skin Color Using Curves
To adjust your colors, open up a curves adjustment layer and pull down the appropriate channel:
Red channel for cyan changes.
Green channel for magenta changes.
Blue channel for yellow changes.
Say you have too much yellow. To lower the yellow number, choose the blue channel from the drop down channel menu. Ctrl+click on the sampler. This will place a point on the curve. This point is what will be adjusted to change the yellow number in the info box. Basically, move that point to the right and you'll add yellow. Move it to the left and you'll add blue.
Here's a visual of the colors each channel is responsible for when working in RGB. Look outside the curves dialog box and notice the color changes on the image of the patio stones when the curve is moved (I've masked the image on the diagonal along the curves dialog box.
Remember that pulling the curve in one direction (adding more of that color) is the equivalent of subtracting the color opposite.
Red channel controls Red and Cyan:
Green channel controls Green and Magenta: Blue channel controls Blue and Yellow: