When film is wound in a camera, static electricity is generated on the film surface. Normally, this electricity is dispersed by the metal rims and rollers that guide the film, and by the humidity of the air. In a camera fitted with a Reseau plate, however, the film is guided by the raised edges of the plate. Sparks cause unpleasant patterns to appear on the film and can be a hazard if the camera is used in an atmosphere of pure oxygen. To conduct the static electricity away from the Reseau plate in the Data Camera, the side of the plate facing the film is coated with an extremely thin conductive layer which is led to the metallic parts of the camera body by two contact springs.
Contact is effected by two projecting silver deposits on the conductive layer.
The Reseau plate, or register glass, is not a new development in photography. What is most remarkable, however, is that the group of Hasselblad staff working on NASA camera projects in collaboration with Carl Zeiss was successful in applying the idea to a small camera - like the Hasselblad 500EL Data Camera. This camera is not only useful in space photography, it is particularly suitable for all kinds of aerial photography. The Hasselblad 500EL Data Camera with its Reseau plate produced a small and comparatively low-cost camera which gave satisfactory results in aerial photographic work.