Multiple exposures layered on identical film stock — analog classic, digital in post now. Creates in-camera blends, ghosting, dream logic without cutting.
Two exposures on the same film frame—for a long time, this was purely camera work, not editing. You set your camera on a tripod, expose the first scene, rewind the film (or with digital: lock the frame counter mechanism), refocus on the second scene, and expose again. The result: two superimposed images in the same frame, merged into a new reality. Classic for dream sequences, transitions without jump cuts, or the supernatural—the viewer sees both layers simultaneously, the brain processing layering instead of sequential events.
Analog, this only works with special cameras or manual trick photography: you have to handle the spool, correctly meter the first exposure (often 50% underexposure per frame, otherwise it gets too bright), mark where the standstill should be. With moving cameras (zoom, pan), it gets tricky—parallax, blur, uncontrolled crosstalk. The pros worked with light value differentials: a dark first scene (e.g., moonlight), then a brighter second scene over it—the eyes follow the brightness hierarchy.
Today, double exposure mostly happens in post—you shoot two separate takes (or load two footage sequences), layer them in the NLE, set the upper layer to Screen or Lighten (depending on the desired effect), and balance opacity and contrast. This gives you maximum control: post-hoc masking, color grading per layer, temporal shifting—things that were impossible analog. However, some DoPs consciously shoot analog-native with double spools or use digital cameras in in-camera RAW mode to preserve optical authenticity.
The pitfalls: overexposure, too much contrast flow between the layers, so that both images appear equally strong and cancel each other out instead of working harmoniously. You need planning—which scene is dominant, which is subtle? Black areas of the first exposure become the projection surface for the second. A face in moonlight, with a city silhouette superimposed above it—that works. Two medium-bright scenes layered—mud. Intention counts more than technique.