In 1971, Mike Mandel released a book of photographs called “Myself: Timed Exposures.” Part of their loose, easy charm has to do with Mandel’s appearance: with his long dark hair and thick-framed glasses, he looks like a cartoon version of a peaceable hippie, rambling through black-and-white Southern California. Though the title prepares you for an onslaught of Mandel, only two of the images show him alone in the frame. The other thirty-seven photographs feature strangers of all types, as Mandel thrusts himself into the bustle and rush of street life, popping up among people like an imp, a groovy visitor from another planet. There he is, shirtless in corduroy cutoffs, smiling with a housewife at a supermarket meat counter, or lying flat on the floor of a library with his arms tight at his sides, students craning to observe this sudden interruption. In another photo, Mandel squeezes onto a crowded bench at an airport, his face blurry, the people on either side of him blurry too, caught mid-laugh. Some of the photos require you to search Mandel out, scan for his identifying uniform of big black glasses and lank hair, as if he were an R. Crumb version of Waldo. Then you spot him: a sliver of Mandel, peering over the heads of a gaggle of young girls at Disneyland or just barely visible in the reflection of a beauty-parlor mirror.