Blending two images so both are visible simultaneously, analogous to multiple exposure.
Technical Details
In analog 35mm film technology, superimposition is achieved by deactivating the automatic film transport after the first exposure. The Canon F-1 camera enabled this via a multiple exposure switch, while modern digital cameras simulate the effect by overlaying RAW files with blending modes such as "Screen" or "Multiply." The exposure time remains constant, while ISO values are halved or the aperture is closed down by f/1.4. In post-production, alpha channels with 50% transparency are overlaid, with the luminance values of the pixels being mathematically added.
History & Development
The first documented superimposition was created in 1860 by photographer Hippolyte Bayard. In cinema, Georges Méliès established the technique in 1898 in "L'Homme de têtes" for ghost effects. In 1920, Fritz Lang developed narrative superimposition in "Der müde Tod" for dream sequences. With the introduction of Technicolor cameras in 1932, multiple exposure became more complex, as each color layer had to be exposed separately. Digital post-processing from the 1990s onwards largely replaced in-camera techniques with software compositing.
Practical Use in Film
Orson Welles used superimpositions in "Citizen Kane" (1941) for the mirror scene in Xanadu to visualize Kane's fragmented psyche. Ingmar Bergman employed the technique in "Persona" (1966) to merge the faces of Liv Ullmann and Bibi Andersson. Modern productions such as "Blade Runner 2049" (2017) use digital multiple exposure for memory sequences, overlaying 4K footage in DaVinci Resolve with Fusion modes. The workflow requires precise camera positioning, as subsequent corrections reduce image quality.
Comparison & Alternatives
Superimposition differs from dissolve (crossfade) by simultaneous rather than time-delayed image presentation. Composite shots use separate takes, while true superimposition utilizes identical film sections. Modern CGI ghost effects replace classic superimposition with greenscreen compositing, offering more precise control over opacity and masking. Split-screen displays multiple images side-by-side; superimposition completely overlays them.