Careful viewers have long observed that in the movies, one can not only watch but read cigarettes like subtitles — translating the action on the screen into another language which the camera registers but rarely foregrounds, a part of the thickness of the medium which is almost never brought into focus. […] The cigarette in the scene serves as a subtext, a mute caption or subtitle, sometimes accompanying, sometimes contradicting or diverting the explicit premise of the action or the open meaning of signs.
Source: wiktionary