Using a frame within a frame is a great way to direct the viewers eyes into an image and add a sense of depth to a two denominational picture . It also allows you to get away from a standard rectangular frame forced on to you by your camera’s viewfinder. Frames come in two flavors foreground and background.
The example used here is a foreground frame. In this example the views eye is directed towards the fisherman in the frame (the intended subject). A wide angle lens may be useful to accomplish this task since it is able to capture a wider area of the scene. The same can be accomplished if the frame was behind the subject (like the arch of a bridge for example) in the background.