You should ask before you take photos of someone.
Hank is at a convention and notices someone cosplaying as a character he likes.
Hank wants to get a picture of the cosplayer.
Hank approaches the cosplayer, compliments her choice of costume and asks to take a picture with her.
Hank takes out his camera and starts taking pictures of the cosplayer.
The cosplayer is flattered and agrees to take the picture with him.
The cosplayer notices Hank and feels creeped out by him suddenly taking pictures.