Wikipedia is a fount of interesting stuff:
This was with a manual-focus zoom lens that I was trying to
use as a macro lens. So I was very determined to get the
focus exactly right.
Going through the pictures later, I kicked myself for being so
single-minded, there was a spider or daddy-long-legs in the
background (which I did not notice at the time). It would
have given me more options if I had spotted it at the time!
@Andy, it certainly would have made for a trickier composition, as I had my hands full already perhaps just as well that I didn't spot the spider at the time.