In the first three shots of the film, Melville sleekly and with great economy presents the protagonists, their motivation, the obstacles, the locale, and their relation to one another in space.
Here are our heros. It is late at night and they are attempting to move unseen. The walls form very clean surfaces and draw the eye in the direction of the first man's gaze.
Here we see what he is looking at. More clean lines, another wall and a spotlight establish they are in a prison—they are about to escape. Our eyes are already trained on the upper right portion of the screen at the spotlight. Now the the corners of the walls draw our eyes downward.
While we are already prepared to look down, the bird's-eye view of the prison guards must be from the point of view of the prisoners. The guards are looking back to the left of the screen, presumably toward the spotlight, which places us in the same location as the prisoners, giving us a clear indication who we are to identify with.
The scene is nearly silent and the efficiency of the camera work and editing are mirrored by the prisoners' quiet exit (or vice versa).