How do you convert the lush greens of summertime Mississippi into the arid golden hues of the Dust Bowl-era South? That was the dilemma facing filmmaking brothers Joel and Ethan Coen as they began shooting O Brother in August 1999. They found their solution at L.A. F/X house Cinesite, which had just developed hardware and software that could recolor their world in postproduction.

BEFORE The process is as simple as the film’s bluegrass tunes. Sitting down at their Pandora Color Corrector with O Brother cinematographer Roger Deakins, Cinesite’s digital artists would isolate a frame within a scene (like the swamp-baptism sequence with stars John Turturro and George Clooney, above) and swap greens for yellows using color-grading software. It’s not as tedious as it sounds: Settings for one frame can be saved and applied to other frames.

AFTER The technology has some bugs. ”We were pushing the colors so hard in going from green to yellow,” says Sarah Priestnall, Cinesite’s director of operations for digital mastering, ”we risked introducing some noise (F/X slang for little black dots) into the picture.” O Brother was the second film to be so chromatically transformed — though maybe it’s the first you actually saw; the 2000 indie Urbania gets the pioneering nod. Traffic and Panic Room have made use of it since.