Originally posted by aherpel I am having difficulty using either a circular polarizer or a ND grad filter on a wide-angle lens (either the 12-24 or 16-50 at 16mm). There is always vignetting. Please tell me what I'm doing wrong because I'm really trying to improve my landscape photography for a trip to Ireland in the fall. Thanks!
You're probably doing nothing wrong, but the 12-24 @12mm is reaaallly wide! It will "vignette" on all but the slimmest of screw-on filters, and for landscapes, the best way to use ND filters is a square system. The reason for a square filter is because graduated neutral density filters (which can equalize the difference between bright sky and darker land) can be moved (in the filter holder) to be anywhere (and any angle) in your composition. If you don't want vignetting, then a larger square system like Cokin Z-Pro is what you want for the 12-24 even @12mm, and can do more than just reduce light overall.
When it comes to polarizers (circular or otherwise), they definitely have a use with wide-angle lenses, so get a very good and very slim one. The reason they might sometimes appear to have less of an effect is because the polarization is most effective when perpendicular to the source of light (the sun), and many folks naively only use polarizers on sunny days near noon! A very wide angle lens might show a full 90-degree spread of the land/ sky - so at the height of day the polarizer creates dark bands in the sky or variations in the polarization effect across the angles of incidence.
However, I've found that my Marumi DHG-Super CPL (slim) could've been welded to my 12-24, mainly because on overcast days, or when the sun is very low in the sky (prime photography times), the polarization doesn't cause banding (if you're aware of where the sun is) and the results are much better than an un-polarized lens. Of course,
the Marumi is one of the best slim-CPLs you can get, so YMMV with cheaper ones.