Why does skin look too red in some portraits with auto white balance, and how can I correct it?

Question

I shot a series of outdoor portraits in hot weather and the subject’s skin looks much redder than I expected in nearly 200 images. The camera was an Olympus E-PM2 using auto white balance. In a comparison photo taken the next day with the same camera and lens, skin tones look much more normal.

In the redder set, the subject was partly in shade while the background included bright sunlit areas. In the comparison shot, the background and overall scene color were different. Neutral objects in the frame seem reasonably neutral, so I’m wondering whether this was really a white balance problem, mixed lighting, the scene colors influencing AWB, or simply the subject being flushed from heat.

What likely caused this, and what’s the best way to fix a large batch of images without individually repainting skin tones? Also, how can I avoid this next time?

user75526 · Answer

Based on the sample images you've provided, AWB appears to be working fine. Neutral objects appear neutral: The plate, the concrete wall, the gravel path, the door, the gray shirt.

You are likely not getting the colors you want because of the color profile on your camera or raw processing software does not match your preferences. Camera and lens selection may also play a role.

Lens Selection

Lenses may transmit different frequencies differently. For instance, some produce warmer colors, while others are cooler. Some lenses also have defects, such as "glow", when shot wide open. Some people find that a soft-focus look is pleasant in portraits.

Auto white balance in some cameras normalizes color differences between lenses. In other cameras, it does not. Setting custom white balance typically neutralizes many lens color differences.

Camera Settings

If you are disciplined, you should set custom white balance. However, if you shoot in conditions with varied lighting, forgetting to change white balance can result in dozens of subsequent shots being ruined or wasting your time in post processing. (How significant this is depends on your workflow.)

Some cameras allow color-shift adjustments to auto white balance. Since AWB on my camera tends to produce images with more magenta than I'd like, I adjust AWB to increase the complementary color, green.

You should also select the color profile on your camera that best matches your preferences. Usually one or two profiles will subdue magenta-red colors. Available options vary by camera maker:

FujiFilm: Provia, Velvia, Astia, Classic Chrome, ProNeg-High, ProNeg-Low.
Canon: Standard, Portrait, Landscape, Neutral, Faithful.
Nikon: Standard, Neutral, Vivid, Portrait, Landscape, Flat.
Olympus (Picture Modes): i-Enhance, Vivid, Natural, Muted, Portrait.
Sony (Creative Style): Standard, Vivid, Neutral, Clear, Deep, Light, Portrait, Landscape, Sunset, Night Scene, Autumn leaves.
_{(Feel free to suggest edits with camera makers and profile names...)}

Cameras also typically allow adjustments to saturation, contrast, highlight, shadows, noise reduction, and sharpness.

Post Processing

The objectionable skin tones are most likely magenta, less so red. Even if the colors are accurate, you may still prefer less magenta.

Many tools do the same thing. The concepts underlying curves and levels apply to nearly every other color adjustment tool. Aside from that, use whatever tool is available or that you like best. Regardless of what you choose, it's helpful to know which primary and complementary colors go together (Red-Cyan, Green-Magenta, Blue-Yellow), as well as distinguish Red-Magenta and Blue-Cyan.

You can reduce the magenta by adjusting curves to increase the complementary color, green, in relevant areas. Use color-layer blending to avoid changing the overall luminosity of the image. Use layer masks to isolate changes.
You can do the same thing by adjusting levels. You can use the "auto" button or select white, gray, and black points with the dropper tool. Then look at each channel to see what the software did to use as a starting point for your own adjustments.
Sometimes desaturating slightly is enough to fix skin tones. Use a layer mask to isolate changes.
Some people like HSL/HSV/HSB adjustments. I don't use them at all because I don't know how to adjust "Hue" to get intended results consistently.
You can also try adjusting temperature and tint. (These, along with saturation, are the main color adjustment tools available in Google Photos.)
Some editors include skin-tone specific tools. If these are available to you, experiment with them until you find settings you like.

Here is the result after adjusting the magenta-green curve, masking to limit the effect to the face, desaturating slightly, and applying a contrast mask: