I own my d700 for 4 years now. Recently I got black exposures ( no image) and a different sound ( louder) from the shutter goes with it. It’s once in a month one or two, but recently on a trip I had 10 in a few hours. The batteries were oke and I used my 28-300. Any ideas ?
There could be a problem with the shutter mechanism, the Stop down mechanism or the cameras meter. I would send the camera to Nikon Service or a Nikon Authorized Service Station to diagnose and fix the problem.
Is it always the same lens, if so it could be the aperture in the lens sticking, not an uncommon problem. Especially if its been exposed to high heat. I'd swap lenses and see if it still does it. I had a 50mm that stuck shut intermittently.