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Nikon specifically recommends not breathing on the glass elements to clean them as harmful acids in the breath can damage the coatings on the glass.
However, I've read on many other websites that it is OK to clean the lenses in this manner.
What are the potential pros and cons of doing it?
NOTE: Shortly after this question was posed Nikon removed all references to the issue of breathing on Nikon lenses from the page at the above link.
If acids in human's breath are enough to degrade Nikon lenses, I think that's the best argument yet for buying any other brand.
I've been involved in photography for 27 years. This is the first I've ever heard of "harmful acids in breath" that could harm a lens. I don't believe I've been living under a rock.
I could be wrong, and my lenses could be days away from disintegrating. When that happens, I'll come back and post a follow-up to let people know that huffing on lenses and using a clean cotton cloth is no long recommended.
Don't hold your breath. Unless you own Nikon lenses, in which case, you'll want to not breathe around them. :)
I haven't done any analisys, but here is my take on this.
There is no doubt that Nikon knows what they are talking about when it comes to lenses and lens care. However, in this case I suspect they are covering their butt. Unfortunately manufacturers are driven to do that more and more because every once in a while someone does something stupid, perhaps deliberately, and some sleazy lawyer hypes it as uncaring giant corporation screwing the little guy and gets a jury to fall for it.
Your breath is saturated with water vapor, which condenses on anything colder. In the winter when the outside air is sufficiently cold, it even condenses just in the air and causes fog. This condensate, whether the fog in the air or the thin layer of microscopic drop on a hard surface, is essentially distilled water.
Now distilled doesn't mean pure, but it will be pretty clean. Only the stuff already in the breath can condense, so we have to consider what exactly is in breath. Most of the breath will be nitrogen, oxygen, and carbon dioxide. Those will remain gasses at normal human temperatures, so what we really want to know is what else is in this mixture in partial-pressure form that has a lower saturation level at lower temperature. That's going to be overwhelmingly water. I'd like to know what acids Nikon thinks are in breath in partial-pressure form. The body has some hydrochloric acid, but that is in the stomach and not in your lungs. The most likely culprit is carbonic acid, which wouldn't actually be in the breath, but could be formed by the condensed water particles dissolving some of the CO2.
Maybe Nikon is referring to this weak carbonic acid, but my guess is that they don't want to get into a case where they said breathing on the lens was OK and then somebody claims damage when they actually got spit on it.
I have breathed on camera lenses many times over many years and have so far not noticed any ill effects. And yes, these were overwhelmingly Nikon lenses.
Ever since I posted this question here, this has been featured on 2-3 websites:
Although I'm not sure if this was a direct result of posting this question here.
Nikon has now updated the support page and removed the statement where it said that breathing on the glass could damage the lens coatings due to presence of harmful acids in the breath.
The way best to clean the front element of your lens is with a lens pen.
Look up on amazon, I think Nikon sells one for around $5. They have special black-carbon powder that you apply on the lens. It basically removes/absorbs any residual oils and fingerprints from the surface of the glass without leaving any micro-scratches (like the ones left by wet-wipes). I'm really scared of wet wipes or breathing on my lens as it might destroy the coatings on the front element.
I'd personally recommend the lens pen and a good micro-fiber lint-free cloth with a very diluted glass cleaner sprayed onto the cloth instead of directly on the glass. Hope this helps! :)
I don't know anything about acid on the breath (that sounds like a Japanese-English lost-in-translation issue to me) but I have noticed that optics I've cleaned with breath-and-cloth tend to be ever-so-slightly hazier than professionally-cleaned optics, over time.
Rather than acidity, I chalked it up to saliva being a poor cleaning agent and the cloths I used being too coarse which caused micro-scratches over a very long time.
The best way to clean lenses, screens, glasses and just about anything else is to use disposable lens wipes.They come in boxes of about 200-500 for 10 bucks or less. Otherwise I breathe on the lens from time to time when in a hurry or I dont have the lens wipes. I've never noticed any harmful effects. But I also usually clean them again with the lens wipes when I get home.
What they won't say is "this statement attempts to cover our arses in-case our lenses come back with fungus or moisture affected areas, which in turn affects the performance of our products".
In all honesty, it depends of the build of the lens. If it's well built and sealed, then breathing on the lens and wiping it will cause no damage to your lens.
However, if it's not well built and/or sealed properly and there is regular breathing on the front element, over time this may cause problems down the track. However, it will not damage the coating of the glass. BUT! Depending on the material used to wipe off the moisture, it may (again, over time) scratch off the coating the glass has.
In summary, the 'acids' in your breath do not damage the coating of the glass.
