She gestured to the nearest picture. "Ordinary celluloid film was optimised for white north-western European skin. The chemical composition was not intended for non-whites, so it didn’t capture us well. We were either over-lit and sweating or shadowy and indistinct. Do you remember Sidney Poitier in In the Heat of the Night ? I mean, okay: it’s supposed to be hot, I get that. But he’s awash—they’ve got the lights dialled all the way up because the film can’t see his skin. Until around the year 2000 they still used white-skinned models for colour balance during processing. Digital cameras changed that, but I wondered how much. I started wondering if there was still a bias—in the chip design or the imaging software’s basic presumptions."