Fri 01-Feb-13 07:41 AM | edited Fri 01-Feb-13 07:50 AM by archivue
Have a look at the aperture tab (plastic thing over the mount camera side), sometimes it's stuck or has a distended recall spring that doesn't bring it back to the original (zeroed) position ? With AI-S lenses, they would work starting say at f/2.8 and it wouldn't be noticeable without extreme settings. G lenses don't use the tab.
Another way to find out on AF-D's, is to move the aperture ring (on the mounted lens), there can be a setting when you don't get the fEE ( f/2.8, f/4, etc.)! After the work on mount and AF module (full disassembly) the tab can get a "hard point", but after a while it may get "broken in" (not broken ) if it's new...
If it's slightly stuck (very low effort to move it all the way and back) it's almost normal. If it's harder you should get it back to Nikon
Edited to add: The bad new is that to repair this little plastic tab and the mechanic that behind, you need a full disassembly !!! (been there)!
When using very often the same lens (or the same minimum aperture value lens), or using G lenses for long time periods, dust and sticky gooey can gather and "stick" the tab, moving it slightly at each lens change should keep "clean".
In old times it was also a ritual when changing AI lenses to verify before mounting, the aperture control pin to see if the diaphragm wasn't stuck at some point (not closing after f/5.6 for example), the "new" tab system is about the same thing and we should have a ritual to verify it frequently !!!