So far so good on the White Balance and skin tone stuff right? In Part II we covered some things about relative coolness/warmness and context, an obvious tip about comparing and choosing a particular skin rendering, and some other contextual things to consider. Today will be a shorter one. Something I have mentioned about four dozen times but don't think I explicitly illustrated. Today we have color temperature versus saturation.
For consistency I'm using Aperture 3 and Mary again in a different setting. I hate the room you see in the screen shot at the top. It's vexing from a color correction standpoint. It has a bank of windows that let in sun and sky on the left out of frame, which is great. Too bad the glass in those windows has some crazy coating that turns it green. On it's own that would be okay. We would just correct it out with some pink. Here's the problem… the bounce back in that room comes from a wall of brick and similarly colored wood that goes around the entire room. That converts the green into an awful and complementary red/pink coming from opposite directions. This is no minor tint it's extremely strong green or pink. Take your pick you can't have it "correct". Oooops - off track, let's get back on point.
In the screenshot above I zoomed into 100% so we can focus on the skin. I left some hair in the frame too as something to evaluate vs the skin tones and the variations we'll be comparing. In this circumstance I was able to get reasonable decent skin tone in that room totally do to the fact that all of Mary's skin in this shot is illuminated by that green flavored sun bouncing back off a white quilt immediately in front of her face. It's so close that it does a good job of completely overpowering any of that pink/red bounce back from the bricks and such. Do note all of the different colors in her hair compared to the dark area under Mary's face lit only by that bounce back – see how red/pink it is…
That first version at the top was my normal or at least the last time I did anything to this set of images. Let's take a look at a bit warmer using the warmth slider on the white balance adjustment in skin-tone mode.
If you were to measure the numbers you would find this made the skin more saturated by what I consider a significant amount relative to the rendition at the top. Let's take a look at a little bit cooler then.
As you would expect, if measured you will find that the skin is less saturated. Why is this? We didn't change saturation nor did we mess with contrast which can raise or lower color saturation. It just so happens that the temperature setup in all white balance controls is centered around a hue that is close to human skin; Sort of orange. If you think back to our playing around with curves adding or subtracting a color makes the opposite color more or less saturated. By taking away that orange you are moving the skin more towards gray. Conversely, adding more orange takes it farther away from gray which is the same as more saturation.
Let's put that in visual terms by going back to the same white balance as the top image and taking out some saturation using the enhance adjustment brick.
As you can see, the effect on skin is similar if not identical to a cooler white balance. For completeness sake let's do the opposite and go with a higher saturation.
Similar to a warmer white balance. I didn't even try to make the white balance and saturation skews away from the center match. They just happened to be about the same. Maybe it's subconscious or something with the increments that I randomly chose. Both the warmer/more saturation and the cooler/less saturation are almost identical - at least in terms of skin color.
One could ask "Well now what?, Which one should I mess with?". As is the case with most things – it doesn't matter much as long as you end up with the result you want. Do what works and gets you to the place you want to be. I will say that if you find yourself adjusting saturation due to skin tones you typically are using a white balance that is too warm. This is the case I find with a lot of people's correction process. I tend to use saturation (usually less) more as an effect and attempt to get the color balance where I happen to think it feels natural whatever that means.
A couple of other thoughts on the matter that are for the more technically oriented. Even though I have mostly skin or skin like colors in the screenshots (skin like being hair, lips, etc - which are surprisingly close in actual hue numbers) if you examine the differences between the color temperature skews versus the saturation skews away from center you'll find that the farther away the color is from skin the less visually affected it is by the temperature changes because of their relative small increments. Conversely they are more affected by the saturation adjustment. Hint - take a look at Mary's lips relative to the skin in the different variations. If there were some primary greens or blues it would be easier to see but I chose to make a very lopsided illustration here of mostly skin like tones.
Here are some of my personal preferences just as a starting point. You already know that I tend to color correct skin based on lighting context. I don't like warm/soft nor do I like cool/hard in terms of light and color combinations. I have a special aversion to another set of combinations. I definitely do not like less contrast with more saturation or the opposite – less saturation with more contrast. Both of these things feel like a special effect to me with the former being hate worthy. Namely low contrast with tons of saturation. Just plain bad. Now let me point out the obvious as one last thing… the more contrast and more saturation in an image the more hair-trigger the skin tones. You will see even a tiny skew cool or warm. Tiny differences in light color will be more noticeable so will actually color variations in the persons skin that are bound to exist. It's usually a really bad idea to ramp up saturation a lot to deal with a color balance problem. It's probably less bad of an idea to ramp down saturation to deal with the opposite but still doesn't look right to my eyes.