It's the final weekend of Tate Modern's exhibition on looking. From the Tate website:

“Exposed offers a fascinating look at pictures made on the sly, without the explicit permission of the people depicted. With photographs from the late nineteenth century to present day, the pictures present a shocking, illuminating and witty perspective on iconic and taboo subjects.”

If you can't make it to the exhibition this weekend here's a video about the show from

the Tate Channel:

Sandra Phillips on Surveillance; Exposed, Tate Channel, 2010