Another Good Way to Clean Your Lenses, and Several Ways Not To
A lot of people have tried to come up with better or perhaps just cheaper ways of cleaning lenses and I by no means exhausted the list of potential ideas last week. Not every idea that has ever been put forth is a good one though. In the interest of completeness, presented here is one lens cleaning method I didn't mention that is worth considering, and several that are probably best avoided.
The Lens Pen
For those dying to know how this week's tip turns out, the LensPen is the good option. As far as I know, it was first brought to market around 10 years ago by International Parkside Products of Vancouver, Canada. Held like a regular pen, the LensPen uses an ingenious dry carbon-black cleaning compound on a small felt pad to clean lenses without liquids. Upon first seeing one years ago, I was somewhat skeptical that it could actually work, but work it does.
For convenience, it also has a brush on the back end to get rid of any loose dust or grit before using the cleaning end.
The makers have contracted an outside consulting firm to test the safety and effectiveness of the LensPen, and their results do look impressive (pdf link). Extensive usage by countless photographers bears this out in real life. I carry one with me for use in the field in case my usual hard-breathing-and-microfiber-cloth routine meets its match in a stubborn spot. Sometimes it's just not convenient to break out the lens cleaning fluid while waiting for sunrise in freezing weather.
On occasion, the LensPen may leave small amounts of a fine black powder residue behind. This is the carbon-black cleaning compound and can be safely removed using the brush on the back end of the pen. It is not abrasive.
My only real concern with the LensPen is that while they work quite well when new, people tend to keep on using them, often long past when they should be replaced. Twisting the cap is supposed to replenish the cleaning compound so the tip will last quite a while, but it's not indestructible. That tip is the very one you will rub on your lens every time you clean it so if it does get dirty somehow I think you could end up with problems. If you like the LensPen, I'd suggest buying a new one periodically just to be safe. Consider it cheap insurance.
These days, LensPens are everywhere. Just about every camera store sells them under at least one brand name. If you've always dismissed them as being just for amateurs, you might want to pick one up and give it a try.
Seeming to cater more to the telescope market than to camera owners, a Wisconsin company named Dantronix Research and Technologies makes a lens cleaner called Opticlean. I've never actually seen this stuff, but have heard of it off and on in both a good light and a bad one. Opticlean is a polymer compound that you paint on the lens element in need of cleaning. After it cures to a plastic film, you can supposedly peel it off using one of the supplied pull tabs, taking with it all the dust, finger prints and other contaminants.
The problem is, it doesn't always turn out that way it seems. I have seen reports that it can sometimes be hard to get all of it off, especially if any gets on the edge of the front element where it meets the lens body. The idea of trying to pick some sort of plastic off the front of my lens doesn't sound very appealing to me, especially when there are easier, safer ways to clean it. Distribution of Opticlean is somewhat limited, so it would seem to be an idea that never achieved mass appeal.
Windex and other Window Cleaners
The short answer is: don't do it. Regular glass cleaners contain ammonia, a chemical that will destroy many coatings used on modern lenses. Some glass cleaners rely instead on vinegar or other ingredients, but I just can't see any good reason to experiment with different cleaners when perfectly good lens cleaning solutions are readily available.
Soap and Water
Another idea best left in the "don't do it" category. Most soaps are far to harsh for use on coated optics.
Diluted ethyl alcohol is often recommended by purists for cleaning lenses. If you get laboratory grade alcohol, this can work, but avoid anything labeled as "rubbing alcohol" as it also contains some percentage of glycerin which will leave a residue on your lens. As with the various window cleaners already mentioned, I just can't see a reason to experiment so I tend to stick with Formula MC or other quality lens cleaners.
Yes, vodka. Diluted similarly to ethyl alcohol, this can indeed work in a pinch. It wouldn't be my first choice though. Save the vodka for after you clean the lens.
Quality lenses aren't cheap, and I see no reason to risk damaging them. Be careful how you clean yours, and remember: doing what you can to prevent them from getting dirty is still your best option.