Problem is: nobody in philosophy of arts / aesthetics gives a damn about film as a material medium. Some are excited by the "possibilities" of digital medium and what it means for the future, blah blah, but the bulk of aesthetics writing on photography is either medium-agnostic or simply takes for granted that film is its natural medium. Obvious, since more philosophical writing on photo is historically coincident with the use of film as the primary support of photography.
So if you want to contribute something to the discussion, you would be better served by using more general work, studying the role of medium in art forms, for questions such as What does marble contribute to the meaning of Michaelangelo's David? Look for people like Kendall Walton, Richard Wollheim, Noel Carroll, and David Davies (his "art as performance" is a tough, but very rewarding read on the role of medium).
Avoid Barthes, Sontag, and Benjamin if you are remotely serious, philosophically speaking.