Do you ever clean the front element of your lens by fogging it up with your breath and then wiping it off with a cloth? If so, you might want to stop — Nikon says the practice could be damaging to your glass. Apparently human breath contains stuff that isn’t too friendly toward camera lenses.
The best way to clean a lens is to use a piece of lint free lens cleaning tissue and a small amount of Lens Cleaning solution. Do not use anything containing abrasives or solvents, only use Lens Cleaning Solution.
First we recommend taking a small blower brush to blow off or brush away loose dust or debris.
Next, place a drop or two of cleaner on the tissue (never directly onto the lens) and then wipe the lens in a circular motion, beginning in the center and working your way outward, removing any marks or smear.
If the above supplies are not available a clean, dry, soft, lint free cloth can be used to clean the lens. Do not breathe on the lens to fog it for cleaning. There are harmful acids in breath that can damage lens coatings. Just use the blower bulb, then brush, and wipe the lens in a circular spiral from the center outward.
And you thought acid breath was only a spell in fantasy video games…
P.S. Some people fog up their lens intentionally for clouded photographs. If what Nikon says is true, it might be wise to breathe onto a UV filter when doing these artificially hazy shots.
Update: Nikon has updated its support page to remove the acid reference discussed in this post.