Quote Originally Posted by John_Nikon_F View Post
I had the same thing happen on an F2A that I owned in 2010. Happened twice, after trying out a 7.5/5.6 fisheye-Nikkor with the mirror locked up. After that episode, it worked fine. I've also had a couple junker Nikkormat FT series bodies do that. Except, with those bodies, you'd depress the shutter release, hear a slight click, then nothing else. Depress the DOF button, and the camera fires.

-J
I can understand the case when you press the shutter release and nothing happens and then you push the DOF the shutter released. That's because the camera is sticky, the shutter release started the cycle but could not complete. Pushing the DOF helps it going.