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.
Zsigmond sought to create a sense of pastel light and subdued contrast appropriate to the film's retrospective 1950s Los Angeles mood.
The MGM 2002 DVD re-release of The Long Goodbye includes an interview with Zsigmond in which he discusses his aesthetic goals for the film and his use of flashing to achieve them.
In the March 1973 issue of American Cinematographer magazine (the text is included on the DVD), Edward Lipnick discussed Zsigmond's technique in detail.
Zsigmond worked closely with Skip Nicholson, then Technicolor's Manager of Photographic Services, to establish an acceptably predictable system to set the level of flashing to be used for a reel.
But, as Lipnick says at the opening of his 1973 American Cinematographer article, "Exposing your negative to varying amounts of light after you have shot it and before you have developed it, without being precisely certain what the results are going to look like, wouldn't seem like a technique designed to reduce the anxiety level of a cameraman shooting a major feature."