Saturn's rings are one of the most spectacular objects in the solar system. Analysis of their origin, evolution, and eventual demise can provide insight into the formation of our solar system as well as planetary formation processes in general. This talk will provide a brief overview of the ring systems of the giant planets, the basic principles of photometry, and how we have applied photometry to Saturn's F ring. The F ring shows a dramatic change in brightness from the Voyager era to the Cassini era, and we attribute this change to perturbations by the nearby moon Prometheus. The talk will conclude by presenting some basic information about these perturbations and how they may have caused this change.