Much has already been written about the piercing human insight of Kirsten Johnson’s Cameraperson. Working with material originally shot for a dozen other films, Johnson refashions the offcuts of her two-decade career as a documentary cinematographer into a patchwork memoir — one that reveals just as much about the woman behind the camera as the individuals who pass fleetingly before its lens. The effect is emotionally exhilarating, but the approach is unabashedly formal — and less has been written about the ways in which Johnson fractionates her footage in order to create a film of clear divisions and implicit rules. […]