Originally posted by ghiaauto Then let's say which lens is the sharpest one! XD thanks
From the looks of it I would think the 18-35. But again, as Rondec and HenrikDK say, almost any lens is plenty sharp when you stop it down - and for landscapes that's usually what you want to do.
I would recommend looking at the works of others and check out the exif of the ones you like the most. That will give you an indication of what focal length you most likely would want, and also what f-stops and exposure times you are looking to match.
Another filter tip would be to get a circular polariser. It may not be that useful on very wide lenses, though, as the polarising effect will shift over the frame and may make especially the sky look strange. And, also as Rondec so eminently shows, the DA 15 really doesn't need a polariser. It has really punchy colours all on its own