> Step 2: > Given: > 1. UV light flares badly (Theorem 1.1) > 2. For general photographic purposes UV light provides > little or no useful information in the final image. > > We can conclude: > > Theorem 1.2 -- Preventing UV from entering the lens is > a good way to reduce flare. > You mean: A good way of preventing _invisible_ flare (by step 2.2). > Theorem 1.3 -- A UV filter will not reduce flare from > visible light, because visible light will > still be reflected by the internal elements. > > Corollary 1.3.a -- An uncoated filter will increase flare > from visible light, because it provides > an additional reflecting surface. A fully coated filter will also increase flare, just not as much. > And in conclusion: > Don's Postulate: You can eliminate all flare from a lens by > simply removing the lens elements. So how, then, does adding an element reduce flare (And I mean visible flare, since I'm not much concerned with invisible flare)?
