Does cleaning solutions deteriorate lens/filter coatings?

Started Mar 9, 2013 | Questions thread
apaflo Veteran Member • Posts: 3,854
Re: Use what you need to

ARShutterbug wrote:

I know that water is sometimes better than stronger chemical cleaners, but I use whatever I need to get the lens clean. In the end, who cares? Just use a standard optics fluid and lens paper. It's not going to make much difference if you have some fancy coatings or not. You can have scratches all over your front element without noticing anything wrong from your photographs.

The lens doesn't need to be "clean"!   Removing dust is nearly meaningless.

But don't kid yourself about how important the coating is, or that scratches have no effect. Wearing off the coating with solvents or excessive cleaning causes the same effect as scratching the lens surface.  The lens loses contrast due to the flare that results.  Tiny scratches cause reflections, as does a lack of the coating.

Dust or dirt on the lens tends not to cause reflections, but rather to just block light transmission.  Your lens, if literally half of the surface is blocked by dust and dirt, will be almost as high in contrast and as sharp as if clean, but it would lose about an fstop of light.  A lens with a large scratch can actually be "repaired" by filling in the scratch with flat-black paint to prevent reflections.  But the tiny scratches from excesssive cleaning can only be fixed by replacing the front element with a new part that has the original coating intact.

Lenses rarely ever need cleaning.  Blowing dust off is quite sufficient.  Finger prints, however, should probably be cleaned to avoid corrosive etching of the lens coating.  Pure water or a very mild cleaning fluid is adequate.  The main thing is to use a brush first and then a liquid to remove all dust and avoid abrassion (scratching) of the lens coating when wiping with any tissue or cloth.

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