I bought a new lens for my D90 today. I've been having a problem using any of my lenses for topdown photography, even though I've lowered the corals to the rockwork in my recent reef reset.
The camera wouldn't focus, and I couldn't even press the shutter button. It was one of those annoying things I've been putting up with for a long time, raising the camera more and more away from the subject. The minimum focal distance was the hurdle.