Excellent cinematography
The compositions and camera angles are quite striking; they make good creative use of the indoor locations. And the lighting, especially in the night scenes, is terrific, especially for a film made 60 years ago-- very complex, subtle, and realistic. Watch the last fifteen minutes, for example. It's a fine example of moviemaking as visual art. Such scenes in many other 1950s and '60s movies (and TV shows) are burdened with simplistic, phony-looking lighting that detracts from whatever emotional effect the after-dark environment was meant to provide. But these guys got it right.
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