At the very end of the film, the extension becomes extremely narrow, focussing on a single point, like a lone spotlight pursuing a character on a stage - the footsteps of a killer in the stairway, which Stewart can hear approaching. Varying the extension to the point of absolute silence is used for achieving effects of subjective sound. The suppression of ambient sounds can create the sense that we are entering into the mind of a character absorbed by her or his personal story. An example occurs in the scene in Bob Fosse's All That Jazz when the protagonist has a heart attack. When extension is used as a sudden contrast, it contributes toward creating a emotional effect.
Some films adopt a single fixed strategy for spatial extension and maintain it throughout.
In Lang's M extension is generally quite limited.