Yeah, the control factor is definitely there, only it's usually about the words and descriptions. I rarely leave the mind's eye pictures to chance.
I'm also a shameless voyeur whether it be via the phone camera (I'm into odd facial expressions and cool backdrops) or via the conversation journal I keep--you know, the snippets you overhear that either have you laughing or wondering WTF? or give you a really cool turn-of-phrase. I carry a moleskine with me and record them on the spot--have used a few in my stories as well, but more than anything, they're fodder for my imagination. :D