A True Picture of Black Skin
«All technology arises out of specific social circumstances. In our time, as in previous generations, cameras and the mechanical tools of photography have rarely made it easy to photograph black skin.
The dynamic range of film emulsions, for example‚ was generally calibrated for white skin and had limited sensitivity to brown, red, or yellow skin tones. Light meters had similar limitations, with a tendency to underexpose dark skin.
And for many years, beginning in the mid-1940s, the smaller film-developing units manufactured by Kodak came with Shirley cards, so named after the white model who was featured on them and whose whiteness was marked on the cards as “normal.”
Some of these instruments improved with time. In the age of digital photography, for instance, Shirley cards are hardly used anymore. But even now, there are reminders that photographic technology is neither value-free nor ethnically neutral. In 2009 the face-recognition technology on HP webcams had difficulty recognizing black faces, suggesting, again, that the process of calibration had favored lighter skin.»
Teju Cole, A True Picture of Black Skin – in Known and Strange Things, Page 146.