Optical and Special Effects - Text 2
The Professionnelle was also fitted with a variable shutter that could be used to produce fades. When employed in conjunction with the camera’s rewind function (the operator simply had to cover the lens, shift the camera magazine strap from the take-up to the supply reel, and turn the crank counter-clockwise), this shutter could also produce dissolves.
Early makers of animated pictures also quickly discovered that they could rewind the negative and expose it a second (or third, fourth, etc.) time, or create composite images by masking specific areas of the image and exposing them at different times. Besides making it possible to create extraordinary spaces and backgrounds, these effects were used to express simultaneity, to bring to the screen subjective visions and to create metaphors and allegories.