Skin Tone, White Balance, Etc. Part I

I know I've already said this about a thousand and four times but just cannot help myself – The biggest difference in cameras in terms of color is white balance. A similar truth is that the biggest difference between color negative films of the same vintage is whoever does the color correction (translation = white balance). Especially true if the process is hybrid, scanned negatives with a density and contrast correction as well. Every thing else pales in comparison in terms of variations in color between cameras. On to the white balance and skin part.

Disclaimers

  • Screens vary, calibration varies, viewing conditions vary. So much so that for 90% of the image I post for illustration purposes I don't even bother messing with color (white balance) unless they are way off.
  • So many people I send images to for purposes other than illustration happen to see them on an iPad/iPhone. I am serious in my thoughts about color correcting to iDevice average instead of my calibrated 27" Cinema. Why not? Still thinking on that though.
  • Taste, motivation, intent, and context of image use also varies by an even greater degree than devices and viewing conditions. If I am working I will color balance to whatever the customer's tastes are - I can usually tell based on track-record or looking at images they "like".
  • My mood changes from week to week. Usually not far because you can't go very far on pictures of people and stay in the range of normal. A little goes white balance tweak goes a long way. There's a caveat which we'll look at here – that's contextual to a large degree. If there is a motivation that's clear in the image of why the color is way off from normal then that usually looks better and more acceptable than a completely neutralized skin rendition. That again is related to my own sensibility.

The Meat Of It

Let's pretend we're shooting using natural light. Which I did for the image I chose to illustrate a few things today. There's 99.9% chance that you will have multiple mixed color temperature light sources all hitting your subject from various directions and blending here and there in various combinations. Let's explore just that for a second using Aperture 3 and it's skin tone white balance modefor illustration purposes.

Take a look at the screenshot at the top. The skin tones and overall color reflected are via the skin-tone mode sample taken from the point you see at the center of the loupe. You can download the image or open in a new window to see it in all it's full size glory. It's too too warm for my taste but this is what some people prefer. I chose that piece of skin because it's lit primarily by the cooler open sky coming through windows to the left of the frame. Let's see what happens if I sample the skin that's lit primarily from the bounce-back off the red/orange wood floor, the warm-white walls, etc.

You knew it was going to get cooler from the build up right? I'll spell it out. If you sample warmer areas of skin it will make the overall color balance of the image cooler. If you sample cooler areas of the skin it will make the image warmer overall. Which one is correct? Neither. Go with what you like, go with what makes sense based on the context of the image, go with your mood of the day. If you are going to show a bunch of them together definitely be consistent unless you change the scene. I happen to prefer this cooler rendition better. Especially for the context of this image. More on that in a bit.

I have previously mentioned that if you happen to be using the skin tone mode of Aperture 3's white balance control that the slider is well calibrated for tweaking skin rendition. The reason is that it's subtle. It gives you a fine degree of adjustment for a little cooler or a little warmer without going crazy one way or another. Typically subtle and fine control is what you want once you are in the ballpark of what your intent is. Contrast this behavior with the neutral gray white balance mode. One tiny little movement and boom huge swings translating to not much fine control.

If you happening to be dialing the numbers yourself in another RAW processor or Aperture 3's temp/tint mode do understand that when the temperature numbers are lower a tiny change makes a bigger difference than when the numbers are big for the same perceptual difference. Said another way a 100 point change when the WB is say 3200K is huge. That same 100 point change is undetectable when the WB is at 8000K. Also beware that for most cameras changing temperature will also necessitate a change in tint. They are linked for most cameras (part of the reason WB numbers make no sense for most cameras in 3rd party RAW processors). Play around - you will see if your camera reacts this way or not. Typically if you increase the temperature number and the green/magenta balance was fine it will now appear too yellow and will need more pink. The opposite is also true.

Gray Cards, White Balance Targets, and WB Presets To The Rescue

If you were thinking "I don't need to deal with all this crap, I'll just use my handy-dandy white balance target - then all will be well in the universe"… Not so fast there. Everything I just described will be exactly the same even if your intent is dead neutral skin. How can this be? How about a few questions that will answer that question… Where are you putting that all powerful WB target? More importantly which way is it pointing? Toward the camera? Toward the window? Somewhere in between the two? That set of decisions is the exact same set of things I just discussed with the skin tone tool.

Point the gray target toward those windows and you will get a warmer overall result. Point it back toward the camera and you will get a cooler overall result. See? This is just the real world when using ambient light. You could always always always make sure you shoot flat so all of the skin in the picture is always only touched by one big light. Kind of boring and almost impossible to do indoors as we'll see. It's also not necessarily a bad thing to have a mix of color temperatures. It can be for sure but there are many factors as to when that looks good versus bad.

Skin Is Not Uniform

How about another monkey wrench into the mix (spanner for those of you in the UK). Skin is not uniform in color. Even those unique individuals with porcelain skin have variations, they're just not as obvious and definitely not patchy. A lot of retouched images look so fake because all of the skin is brought into what looks like exactly the same hue… part of the complete recipe for plastic.

Here's a tiny little variation from that last screen shot…

It's a subtle difference, it's a hair pinker. You can see in the center of the loupe the sample was from an area that was a little more yellow relative to the last sample. As you might remember from the remedial color math in the curves posts, yellower means more green. If using the skin-tone mode, choosing a patch that is relatively more yellow will result in a pinker overall color balance. If you go opposite and choose a pinker area it will result in a more yellow color balance. If you are dialing the tint numbers yourself that's how you make the skin either more yellow or more red - with the tint control. See how valuable that color math stuff is?

For the sake of completeness here's a screenshot from a pinker area.

As you can see I am not choosing any of the areas that are crazy different like the edges of Mary's ears or the reddish/pinks under her neck. I'm getting subtle differences. Those areas would give me wild swings. If I wanted to reign those patches in I would use a curves control and brush it in.

Tricks And Tips

Way more tips as I'm not into tricks. I don't even like that word in photographic contexts. At some point in the above blather I mentioned I preferred the cooler rendition. That's partly my own aesthetic and taste but it's also driven equally by context. The context here is soft window light. This almost always feels cooler and bluer in the actual scene so erring on a cooler or more neutral skin rendering feels more natural to me. If there was a different motivation like a bunch of sunshine streaming in, even if not directly on the subject, that would imply a warmer context. Why? because those conditions are way way warmer when you are in that setting. Again unless there is some obvious reason the viewer can see where it should be different. Stay tuned for Part II and we'll talk about that some more.

Within the overall context there are obvious flavors and a little bit cooler or warmer goes a long way. You may have the same desire to have the skin tone rendition match the feel of the lighting in your image but want it just a hair warmer or a hair cooler than I like it. That's one of the reasons I like the calibration of the skin tone WB slider in Aperture 3. It allows for that fine tuning with a lot of control.

All of us go bleary eyed after a long session of color correcting. Our eyes start to play tricks on us in various ways. Especially if those color corrections are across various people in various scenes. Here's a quick gut check as to how far into the weeds you might have gone – check out the hair of your subject. Hair color is not that hard to remember unlike a lot of colors. If your average light brown hair type person where it doesn't go too far one way or the other starts to look crazy red you might have gone overboard on the warm - great if that's the effect you want but if not revisit what you are doing. Is that blonde still blonde??? Blondes with lighter skin are easy to make way to red because higher luminance skin is harder to tell what hue it is. The hair can be tell-tale. Just check out the difference in Mary's hair from the top shot that I consider too too warm to the one I consider more to my liking. Fact - Mary's hair is not red, not even a hint.

Part II coming soon - as usually feel free to comment/question so I get part II right…

RB

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