Dust will hardly affect image quality, and apparently even pros use scratched lenses without any issues. The risk is that, if left there for long enough, or if they start to 'stick' because of other contaminants, moisture etc, they may not be easy to remove with just a blower or a brush alone. And when the cloth goes over that, the lens is certainly going to get scratched.Originally Posted by wong1979
The choice is up to you, but personally, I'd rather take the safer route and not let any dust on the lens in the first place. Best defence is not to get hit, as they say.
Just out of interest, are you doing long-exposure night photography or handheld? How badly does the flare degrade your image? Any examples?