How can the action of images be conceived? In this article the author rejects the concept of effect which is often used to measure the impact of images. Instead, she considers the operativity of signs and specifies the definition of the concept of effect with reference to Austin's theory of speech acts. The difficulty lies in conceptualizing the action of images in the form of language acts, in the broad sense. This theoretical reflection refers to the pragmatic approach to language and draws on the analysis of an example of images from TV reports. It questions a particular language act, disclosure through images, based on the announcements of the capture of prisoners of war on Iraqi, trans-Arabian, US and French TV channels, and the way in which their meaning was performed by various publics.