The article focuses on a collective project carried out for several years by a multidisciplinary team, which has given rise to three editions of summer schools on the theme of «Policy of the Urban Ambient». The approach of the summer school consists of collecting audiovisual material that allows for the problematisation of an aspect of the city that hosts the summer school, in France or in Belgium. The article proposes a reflexive analysis of this experience according to three problematization axes: the auctoriality recognized in the results of the field survey; the formalization on which it is largely based; the interpellative power that is lent to it in reception. It appears that field semiotics is not so much about describing or even effectively revealing the regimes of meaning that structure an environment, as it is about bringing these critical effects to bear on the field of enquiry as much as on the enquiry itself as a field.