Can i use isopropyl alcohol to clean a digital camera lens?

no it can leave smears, just use a cotton lint free cloth, if you need some kind of moisture use your breath but dont use alcohol

in the manual
it tells you to use a damp soft cloth

You can, but not recommended.

No

Absoutely not!

Breath and a clean cloth

no....

Camera lenses are protected with coatings applied at the factory to resist scratches and reduce glare and other light problems. A harsh chemical like alcohol could damage these coatings.

The proper thing to clean camera lenses with is camera lens cleaner. There is a technique to it to avoid damaging your lens. (Don't just dump lens cleaner directly onto the lens, for example.)

Visit your local camera shop and ask to buy some lens cleaner and get shown how to clean your camera.

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http://www.lenslenders.com