Striking photography
This movie was made long before hand-held motion-picture cameras and the Steadicam came into existence. The commentary on the DVD accompanying this film tells the technical details of its filming (in ~1947).
Experienced and new actors and actresses instructed NEVER to look into the camera lens, were told to do exactly that for this film. For interior shots, the camera was mounted on a 2-grip dolly ("with Western wheels", according to the commentators) that had to maneuver the relatively large camera (often for panning) into tight spaces.
The camera was Philip Marlowe, and he was rarely imaged, except when reflected in a mirror, or shown as a shadow on a wall. Director (and star) Robert Montgomery often sat below the camera, so that all actresses and actors got more of the feel of actually "talking with Marlowe". Many very long takes appear, which are often hard on performers having to know many lines of 2- or 3-person dialogues, while essentially talking to themselves.
MGM is definitely not known for film noir. But, this noir venture showed the 1947 creativity and technical competence of this studio known for its "classy films".
There was as much talent behind the camera as in front of it in this classic.
8/10.
E pluribus unum