How important is it to have a coatings on all your filters? A plain UV filter might cost $10 while an SMC filter would cost $35. I can't see how it would matter much on the outer surface, a little bit of light would just be lost. But on the inner surface?
-- "A nice adaptation of conditions will make almost any hypothesis agree with the phenomena. This will please the imagination but does not advance our knowledge." -- J. Black, 1803.
