This is just such a brilliant photograph. The timing of the shot couldn't have been better, you can imagine that the woman in the advertising poster has come alive and suddenly pulled back the curtain. The noise making the cleaner turn around but he sees nothing.
Apart from the humoristic aspect of this image, I appreciate how photographer Rien van Voorst has managed to get the exposure of this shot spot on, specially with the dark tones of the cleaner's skin and clothes and all the smooth light surfaces around him. This is a well taken and fun photograph.
Rien is a talented street photographer who uses light and composition in a way that elevates his photographs to a new level. If you like street photography I strongly recommend you use the link above to see the image on Flickr and take your time to browse through the rest of his work. You won't regret it.