How Kodak's Shirley Cards Set Photography's Skin-Tone Standard : NPR
by thenewgreen
For many years, this "Shirley" card — named for the original model, who was an employee of Kodak — was used by photo labs to calibrate skin tones, shadows and light during the printing process.
"She was the standard," Garcia says, "so whenever we printed anything, we had to pull Shirley in. If Shirley looked good, everything else was OK. If Shirley didn't look so hot that day, we had to tweak something — something was wrong."