How Tough Is Glass?

We tend to treat our glass as holy relics, being reluctant to clean and extremely careful when we do. Those of us old enough to remember when almost everyone routinely wore ties will remember cringing seeing a photographer clean his lens with the end of his tie.

Truth is, glass is pretty tough. Your windshield stands up to being scraped across with windshield wipers when it's covered in dirt , you clean your plastic glasses every day, yet years later, you are still able to see through with minimal if any impairment. OK, maybe your five year old windshield shows a bit of flare when driving into the sun, but consider the abuse, and a lot of the windshield damage is not the wipers, it's small rocks coming up and pitting the surface.

Even if you do get a major scratch on a lens, it's possible to paint the scratch black (so it doesn't cause flare) and the impact is negligible.

Modern lens coatings are pretty tough too - my glasses are multicoated and two years later the lenses look pretty darn good.

Bottom line: you have to work pretty hard to really mess up a lens. Probably the single biggest reason to fret about the surface is if you think there is a possibility of selling the lens down the road, in which case, a pristine surface does add to the value, but not to the quality of the lens. If selling a lens on isn't important, then go ahead and clean when you need to, and if you happen to not have lens tissue, go ahead with the corner of your shirt - better a clean lens and a good shot than an untouched lens and flare spots in your image (especially with wide angle lenses).