Frame Within a Frame
Using an element in the scene — a doorway, arch, window or overhanging branch — to surround and isolate the subject.
In depth
An internal frame does three things at once: it blocks distracting surroundings, it adds a foreground layer that creates depth, and it directs the eye inward because enclosed shapes draw attention. It works whether the frame is sharp or thrown out of focus, and whether it is bright or dark.
Examples in practice
Shooting a street scene through an archway puts a dark border around the subject and adds an immediate sense of depth.