So my Nikkor 70-200mm f/2.8 on my D90 is ALREADY dusty. I can see a few specs, and one rather large spec on my lens behind the first piece of glass. Recently I purchased a UV filter to protect it, but anybody got any tips on keeping the lens clean? Whenever it isn't being used, it has the lens cap on, a filter, and it is in a bag. Tips? Also, [this is aimed at switchfx], Is it really going to make any difference?