In this essay I am investigating how a theatre photograph represents the play and how to interpret a theatre image. It starts with some theoretical reflections on theatre photograph in general and after that I regard it in theoretical context to get tools for deeper understanding. Mainly I am dealing with the ordinary theatre performances and the common photograph's documentary practices, which is already losing ground to the marketing department of promotional images. I examine the Peircean concept of three main modes for understanding the signs conveyed by the photos and which elements make up the language of photography. Finally I analyse one theatre photograph from the play The Celebration and make some concluding remarks.