Though DeCarava was methodical in his picture-taking, it was in the darkroom that he discovered himself as an artist. Though he began by printing his black-and-white negatives as most photographers did, trying to squeeze as much dynamic contrast out of each frame as possible, he tired of the brittle-looking images that resulted. Encouraged by another photographer, Homer Page, DeCarava began to experiment with moodier hues, leaving his pictures deliberately underexposed. Soon he was spending days at a time in the darkroom, delving deeper and deeper into the possibilities of a single negative, playing with the age-old chemistry of silver gelatin prints and light – even where light was almost non-existent. “The difference between me and other photographers,” DeCarava once said, “is that I refuse to accept darkness as a limitation.”

The images he produced are like little else. One picture from 1952, created after days of effort in the darkroom, is simply entitled Sun and Shade: two children playing on a city street, seen from high above. A thick swath of shadow divides them like a wall. An image captured nine years later, Coathanger, is more quietly beautiful. We see the interior of a diner, row after row of banquettes receding into the gloom, with a solitary wooden coathanger catching what might be the last of the sun. So many different tones are visible in the print, from powerful coal black to the palest dove grey, that it feels like you might never get to the end of them.

“Somewhere in the process of developing the image, making it appear, playing with the chemicals, the picture spoke to him, told him what to do,” says Sherry Turner DeCarava. To call him a black-and-white photographer does him a disservice, she adds: “He said that most of the images that seem black aren’t black at all; they’re a very a dark grey. Those greys were his medium as an artist.”