Bipack

[1] Eastman, Agfa, Gevaert, and DuPont all manufactured bipack film stocks for use in color processes from the 1920s onwards.

This method, in conjunction with a static matte placed in front of the camera, could be used to print angry storm clouds into a background on a studio set.

The magazines allow the separate loading of exposed and unexposed stock, as opposed to winding the two films onto the same reel.

Industrial Light and Magic used a specially-built rig built for The Empire Strikes Back that utilised the method to create matte painting composites.

Various improvements and extensions of the process followed, the most famous being Carroll D. Dunning's, an early method built on the bipacking technique and used for creating traveling mattes.

This yellow dye image is exposed on the negative by the blue light from the backing areas, but the yellow light from the foreground passes through it and records an image of the foreground at the same time.The Dunning Process, often in shorthand referred to as "process," was used in many black and white films, most notably King Kong.