The Science of Skin Tones

Written by Mike Moon

OK. Warning … This is about to get technical. But I want to explain how we achieve perfect skin tones for Lit Weddings, so that you can feel confident in our expertise. It begins with understanding the qualities that make up light and also understanding that once bad skin tones are captured in camera, they can’t be fixed in post later.

Lights have three things: color, quality and power. Color in photography is defined as “temperature” (Kelvin). I custom balance my camera on fly, by eye. Namely, orange lights are 3200K, when they start to turn yellow they’re 2700K. If they’re white, they’re 5000ish. I know this is true. So if a light is yellow/orange, it’s about 3K. Now, as I set my camera temperature all day, I’ll notice that the sun doesn’t remain the same temperature. High noon is about 5500. Sunset is at the top of the Kelvin scale for your camera, roughly 7Kish. So I have to adjust my camera all day if I’m outside, as the sun changes. Just like I have to adjust it again after sunset when I move indoors to work under light bulbs.

Then there’s the quality of a light. It’s defined as “Color Rendering Index” or “CRI”. It’s the percentage of the full color spectrum that a light source emits.

Now, lets talk about a lightbulb. A traditional incandescent light bulb gets its source from a chemical reaction, electricity and gas. Or electricity and a burning metal element. The type of metal that’s burning makes a difference too. The resulting light is not inclusive of the entire light spectrum. Fire does not emit 100% CRI. One only needs sit next to a campfire and take photos with the intent of getting perfect, real life skin tones. Without a flash involved, that’s impossible. A camp fire has a horrible CRI value.

Cameras only pick up the colors that are exposed by the light source involved. Viewing skin tones under a low CRI-value light bulb is like viewing a photo of someone’s face on a color monitor that’s missing 30% of its color. The colors emitted from a typical light bulb is about 70% CRI, meaning that the camera doesn’t receive information for 30% of the color. The first color lost to low-quality light sources is pink, so skin turns orange quickly. Flashes, on the other hand, are always 100% CRI. So the goal is to override the bad light in a room with your camera settings and then replace it with good flash light.

Outside on a cloudy day, light is predictably 100 percent CRI and 5500Kelvin. That’s why natural light shooters have more success outdoors than indoors, which is full of bulbs that are not 100 percent CRI. They also probably don’t set their color temperature under those lights, meaning that they struggle with low-quality lighting and a bad color cast. Using Flash properly solves indoor lighting color problems. In many cases, natural light shooters will move outdoors to get to 100 percent CRI instead of knowing how to correct for low-quality light and color indoors with proper use of flash. This is problem after the sun has set, when there is no more natural light to be had. - As is the case during most receptions.

Different chemicals emit different colored fires. Different bulbs therefore are made differently. Most cheap ones are about 70CRI. that means 30% of the true light spectrum is never emitted. Regardless of its color temperature. You can buy light bulbs that are perfect CRI, but they cost upwards of $50 each for a regular 100watt bulb.

Flourescent lights emit as little as 60% CRI and their color is completely different than a regular light bulb. This is because they use an electrical charged gas to make the light. The gas is different than the gas in a regular light bulb. So the fire created is different color and quality. LEDs are getting really good at creating light that’s closer to 97% CRI, but no LED is even remotely as powerful as a Paul Buff Einstein 640-watt-second strobe, for instance. Not only is the strobe also 98% CRI, but it’s 640watt seconds. it can light an object at ISO 100, F22, perfectly. And that object will be perfect color. 100% accurate to real life, out of camera. Not all strobes are the same. An average speed light is 5500K, close to 100% CRI, and 70 watt seconds.

It’s gets more complicated when one considers that CRI values, at the camera level, are very much affected when a sensor gets over saturated. So I could have a 100% CRI light source, at high noon, but flare my lens by pointing it too much into the sun, and blow out a corner of your photo. Where skin tone is involved, I will lose upwards of 80% or more of your CRI value and that person’s skin will never look like real life. — The photo will have that washout, sun-flared look that presets turn ugly orange so easily. It was all the rage in millennial wedding photography for years, but it’s starting to lose its appeal.

The one thing that never loses its appeal is a true-to-life, true-to-color skin tone done in camera under any lighting condition. Only certain light sources can afford that short of using a flash. That’s the power we have as photographers: To FIX light all day as we encounter various percentages of reduced quality, and different colors, everywhere.

It’s particularly important because bad skin colors caused by low CRI values cannot be corrected later, since the skin tone color data is not present in the RAW files. This leads many natural light photographers to convert their indoor photos to Black and White, - to hide the bad skin tones. Or they’ll hit it with a filter they buy online, and pretend like it’s their style. That’s certainly a popular method of ignoring the implications of CRI and color temperature...

At Lit, we just correct for color problems in real time, while we work. That’s the professional way to handle it.