Flashing (cinematography)

In cinematography and photography, flashing is the exposure of the film or digital sensors to uniform light prior to exposing it to the scene. It is used as a method of contrast control to bring out detail in darker areas. This adds a bias to the overall light input recorded by the sensor. When used for artistic effects, it can be used to add a colour cast to shadows without significantly affecting highlights. Flashing is usually described as a percentage of exposure increase to the film's base fog level. While the flash itself is often a neutral color temperature, the flash exposure could be any color: the color of the flash will be imbued disproportionately into the shadows of the image.

The effect is produced by adding a small and even level of exposure to the entire image. Since exposure levels increase logarithmically, this tiny level of additional exposure has no practical effect on an image's mid-tones or highlights, while it shifts the darker areas of the image into the practical sensitivity range, thus allowing darker areas of the image to show visual detail rather than uniform blackness.

Flashing can be applied to the before, during, or after principal photography of a motion picture, although always before the film is processed. When applied before or after shooting, this is generally done by a film laboratory. The level of flashing needs to be tested beforehand and subsequently moderated appropriately against the light levels of the scene, or else it risks having minimal impact if too low or making the shadows "milky" when too high.

Adding a general overall exposure of light to an photosensitive material to alter the material's response to a captured image is a long-known technique. Photographer Ansel Adams describes the use of "pre-exposure," to make details visible in a darker area of an image, in his text The Negative (rev.ed. 1959). For more, study astronomic photographic techniques when silver-halide emulsions on glass plates were the available tool. With modern digital sensors that can capture high dynamic range, it is rarely used.

This only applies when the film stock is exposed to low amounts of light in a laboratory.

On-set flashing solutions include Panavision's Panaflasher, which is mounted in between the camera body and the camera magazine throat, and Arri's Varicon, which functions as an illuminated filter and can be viewed directly through the viewfinder for manual setting of the flash level.

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