Originally posted by jshurak You can rotate the cokin filter system around to adjust for a not straight horizon.......But HDR will work to, but its a little more work.
I meant a straight line horizon, not a horizontal one. The site I linked to has the example image of such situation. If you use an ND grad, the mountain range, and the tree section on the right area will not get enough detail.
Personally, I don't use much PP for my picture except minor exposure adjustment. However, HDR is the one method that, I believe, would accomplish more than any simple equipment out there. After all, it gives you a higher dynamic range.