If you’re examining a person’s fingerprints, palm prints, face, and irises, you need to understand melanin.
The Cleveland Clinic goes into great detail on melanin, but for now I’m going to concentrate on one item.
There are three types of melanin, two of which affect the skin, eyes, and hair.
Eumelanin. There are two types of eumelanin: black and brown. Eumelanin is responsible for dark colors in skin, eyes and hair. People with brown or black hair have varying amounts of brown and black eumelanin. When there’s no black eumelanin and a small amount of brown eumelanin, it results in blonde hair.
Pheomelanin. This type of melanin pigments your lips, nipples and other pinkish parts of your body. People who have equal parts eumelanin and pheomelanin have red hair.
Melanin obviously affects the coloration of your skin, although some parts of your body (such as your fingertips) may have less melanin than other parts (such as your face).
Concentrating on fingertips and faces (and ignoring irises for the moment), let’s look at a situation where we use an optical mechanism (such as an optical fingerprint reader or a camera), along with available illumination, to photograph fingers and faces of people with varying skin tones.
But what if your entire photographic system is based upon reference materials optimized for light melanin levels? As late as the 1970s, Kodak’s reference materials, called “Shirley cards” after the first model, used to exclusively white people.
In the 1970s, photographer Jim Lyon joined Kodak’s first photo tech division and research laboratories. He says the company recognized there was a problem with the all-white Shirley cards.
“I started incorporating black models pretty heavily in our testing, and it caught on very quickly,” he says. “It wasn’t a big deal, it just seemed like this is the right thing to do. I wasn’t attempting to be politically correct. I was just trying to give us a chance of making a better film, one that reproduced everybody’s skin tone in an appropriate way.”
So hopefully today optical devices are properly capturing fingers, faces, and irises of people at all melanin levels.
Or is this wishful thinking?
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