Frame in a Frame Research

 Framing in a frame is used to draw the viewers attention to the main subject of the photo. Main elements of doing this are doorways, windows, tree branches, mirrors, and architecture. Most often, what the frame does is add context to the image. This allows you to understand where it's taking place and if there's aspects of culture involved. Doing this adds another layer of depth to photos by isolating the main subject away from everything else. 

Examples:

This image uses multiple layers of framing to create a more intense depth.

This image uses a train window to frame a woman sitting on a train while reading a book while adding movement with the woman on the outside. 

This photo uses tree branches to capture an image of a child jumping outside in the nature.

This image uses a car door/window to isolate the man for a portrait photo. 

This image uses the opening of a canyon to make another canyon the main subject of the photo.