I agree with Zen, if he had a legit reason for being there he could have knocked on her door to ask her permission since she was home. If he found that she wasn't home, he should probably still leave a note explaining what he was doing in case neighbors noticed and reported it to her when she returned. I'd find it creepy too if a stranger was taking pictures of my home without permission. Hopefully he's learned something from this experience because I've met homeowners that have a policy of shoot first and ask questions later.