I almost never use snap focus for this reason - it is very hard to know exactly how fast a press will switch modes.

^ At least batman hasn't lost his marbles. (Are those pottery-fired marbles btw?) Very effective/affective processing to surround him with light. Batman blown out from behind.
Gretchen Menn - Zepparella by tOny endieveri, on Flickr
Angeline Saris - Zepparella by tOny endieveri, on Flickr