Hello UHH friends,

I suspect there may be a few of you who have dropped a lens and have considered doing your own minor repair with a dab of glue. I think it would only take the tiniest dab with a toothpick to re-secure the casing over the Focus switch on the side of the lens, but do I dare? The lens survived a ten inch drop onto a granite counter very nicely, except for the Focus switch, which is loose and can fall off. I took it into a camera shop yesterday, no one one the premises does repairs, but they would happily send it away for a tidy $330 repair fee! What would you do? Wisdom and sympathy accepted :)

Is it OK to use your breath to clean your lens?

This question arises from time to time here on UHH and opinions vary. Some think it is OK and have been doing so for decades with no problems. Some have heard from experts that there is acid in your breath that will damage the coatings on many modern lenses.

Many years ago Nikon once published in a manual that they do not recommend breathing on their lenses as it may damage them. Nikon seems to be the only manufacturer that has put that in writing.

So what's the correct answer?
A) Yes, if you really really have to and do it correctly.
B) No, not as a matter of routine or as a substitute for more proper methods.

Here is why:
The real concerns with breath condensation on optic glass are:

1) Not properly removing it immediately afterwards and polishing the lens. Condensation can evaporate quickly.

2) If you have to breath on it, then you probably don't have the right gear to clean it with you (your shirt tails are not suitable)

3) Using an improper technique can allow small drops of spittle to be exhaled onto the glass. To avoid the enzymes from forming organic acids they need to be cleaned. Once you get folks think they can all but spit on the lens to clean them (like they do with glasses sometimes) problems may occur.

For all of these reasons and many more, keeping a Skylight or clear filter on your lens at all times is the best solution. I rarely clean my lenses as they are protected by filters (which I clean often).

Bottom-line: Only use condensed breath on your optic glass if you really really have to. That should be never if you are prepared and carry single use wipes and keep a filter installed.

I hope this helps clarify things.

PS: What is not often mentioned on these forums are fingerprints. If left on the coated glass the oil from your shin is slightly acidic and as it oxidizes become more acidic. Over time fingerprints can etch the coatings and leave almost invisible marks that will never show up directly on the image because they are too close to the image plane. But they can create minor flares which will be visible from time to time. Fingerprints should always be removed from your lenses (and filters if you wish to make them last).