all these questions about filters and stuff, i've come up with a couple of my own.... I'm pretty sure my lens focuses externally, and i know polorized filters dont seem to be a problem with this (since i can turn the filter after focusing) but what if i used a graduate or split ND filter? do they rotate like a polorized? or is it fixed? i take mostly landscapes and i'm reasonably sure that a split ND is what i need...but i need to clarify some things before i buy one...or some Thanx!