I cannot for the life of me figure out why there are times when my D5100 can't release the shutter. It doesn't work anywhere like my D300S or my D700 (although a little like my D5000, but not quite as finicky). I have tried all the auto focus modes (AF-A, AF-S, AF-C) and it will not reliably release the shutter unless I have an edge in the composition and have recently focused it (I have assigned the AE-L/AF-L button to command the focus and disassociated the shutter release button from the AF function - and of course this is a standard method of use for the D300S and D700).
This has recently caused me grief when trying to capture a blank wall to test my sensor cleaning process/result. I have to resort to setting it to manual focus to take any picture of "nothing."
Hot damn guys! Thanks Brian and Marty! It sure was set to focus. That has to be the problem. I set it to release, and even though I've not tested it yet, I'll bet big bucks that the problem is resolved. Thanks again guys.
>Hot damn guys! Thanks Brian and Marty! It sure was set to >focus. That has to be the problem. I set it to release, and >even though I've not tested it yet, I'll bet big bucks that >the problem is resolved. Thanks again guys.
I was wondering about the same problem! You got a twofer--this was just the answer I was looking for.