#2. "RE: D Type Lens and Manual Focus" In response to Reply # 0 Mon 07-Mar-11 08:15 PM by gkaiseril
Have you looked at page 269 of your camera's reference manual?
Note the column headings for the two columns under the "Focus". One is "AF" the other is "M (with electronic range finder)". This means you can refocus and hold the focus lens. If you want you can set the focus mode selector to 'M' and just focus the lens but you will be able to take the shot even if focus is not obtained.
#3. "RE: D Type Lens and Manual Focus" In response to Reply # 0
I too have on occasion forgotten to switch to manual mode on an AF (Not AF-S) lens. I have gotten spoiled by the new G lenses with the A/M setting that lets you fine tune with manual without having to turn of the autofocus.
I always notice when I feel the increased resistance and stop immediately. To date I have not seen this adversely impact the operation, although as instructed by the manual I try to avoid doing it.