Based on a field survey dealing with the “social cinema” category in France in the years 1990-2000 and by mobilizing some cases of films featuring mobilizations, this article proposes to study under what conditions and how films can be a material for researchers in social sciences. Like other more traditional materials and despite the proximity of view between the artistic and the scientific fields, films (whether documentary or fiction films) are not providing direct access to the "real". In order to constitute them in sources, the researcher has to combine internal and external analysis, to link their conditions of production and of reception. Beyond this methodological proposal, cinema taken as an object (and not only as a source) can be the place of mobilizations and can open an heuristic field of researches to work on collective action and to study activists’ know-how in a new perspective. Indeed “social films” from production to reception are the subject of multiple appropriations which can correspond to a process of politicization.