> I don't think you'd want to put either Rain-X or a silicon compound on a > photographic lens, there might be a reaction with the coating.
I've had a lot of experience trying to keep the front element of the lenses I've used on whale watches dry, and it's not easy. Whether the drops are from rain or fog (annoying), salt spray (worse, since it smears a bit, as compared to rain water), or whale snot (don't ask - <g>), I have found that nothing works as well as a pocketful of old, no-longer-used-by-Fred handkerchiefs. Admittedly, I tend to not take some of my more precious lenses to sea, but I still am concerned about front element abrasion on those that do get "impressed" into marine use (pun intended - sorry). However, since dust (often abrasive) is generally not much of a problem offshore, I have found that Pentax SMC and the coatings used on my VS1 and Tokina AT-X lenses (as well as the HMC coating on several Hoya filters) have all stood up well to numerous handkerchief wipes. (It's worth using only soft, well-worn handkerchiefs, and avoiding newer, "stiff" handkerchiefs, methinks - it's better to scratch your nose than to scratch your lenses - <g>.) Fred
