Sydney, as seen from my balcony five minutes before ‘lights out’ in Earth Hour 2009, with the camera set up to take what it believed was a +0EV shot:

Exact same exposure, aperture, ISO and perspective (except for somebody nudging the tripod) as previous shot, after all the lights that were going to go out had gone out:

Half an hour after the lights came back on:

(Note for keen observers: on top of the bridge there are two flags. The one on the right is a special “Earth Hour” promotional flag. This flag remained illuminated throughout.)