I love when certain technique gets used on purpose – when it is used not only because you can, but because it helps to tell the story, and color contrast enhancement (CCE) in Seven is exactly that case.
Detective William Somerset (Morgan Freeman) is at the end of his career, but he gets one last case to solve, together with young detective David Mills (Brad Pitt), he is searching for serial killer John Doe (Kevin Spacey), who kills his victims on the basis of seven deadly sins.
The overall atmosphere of the movie is literally dark. First, the serial killer John Doe is brutal and fanatic, but at the same time, he is very clever, intelligent and accurate – I can hardly imagine worse villain than him (Joker from Batman gets honorable mention here). Second, most of the scenes happen in dark interiors, in certain scenes, you’ll see only flashlights of the detectives.
But outside it doesn’t look any better. Dirty, violent and depressive city, where it constantly rains.
To further support this dark mood and atmosphere, some theatrical prints were created using silver retention process. This technique increases the contrast – it makes dark areas darker and light areas lighter (similar to blending mode overlay). In other words, the blacks are more black. Further, this technique adds more grain to the film print. Maybe you haven’t noticed this effect at first (I haven’t), but you can certainly feel it on emotional level. So long story short – CCE increases the contrast (drama) and grain (roughness).
P.S. I’m almost 100% sure, that the director David Fincher and cinematographer Darius Khondji discussed the CCE technique before they shot the movie. This only proves, that David Fincher knows how to tell a story in a cinematic way.