This article investigates deep conceptual affinities between diaries and cinema by reading Philippe Lejeune’s minimal definition of the diary as a “series of dated traces” against theories of film. I propose to regard written testimonial traces and filmic documentary traces as indexes of different modes and complementary semiotic orders. This view will shed light on borrowings and exchanges between filmic documents and personal testimonies, and account for the invigorating role of the diary as a genre of personal and medial explorations.