Now we see through a glass, darkly...
- Apr 5, 2016
I'd recommend going with a decent 100mm filter holder and 100x150 mm graduated ND filters, which are far more useful for seascapes and landscapes than screw-on GNDs. GNDs in general are better for landscape than straight NDs. You can get CPLs that fit the 100mm holder, too. Then the only thing one needs each time they get a lens with different thread sizes is an adapter ring for the holder.I would recommend for land and seascapes
a) Canon 10-18mm (67mm filter thread)
b) Canon 70-200 f/4 (67mm or 72mm filter thread)
I would recommend screw on Neutral Density (ND) and Circular Polarizer (CP) filters
For ND (3, 6 and 10 stops) I would recommend either Hoya (ProND 8, 100, 1000) or Breakthrough (X4-ND 3, 6 and 10-Stop)
For CP, I would recommend Breakthrough or B+W XS-Pro Kaesemann.
I would recommend getting two sizes for 67mm filter thread and 82mm thread with couple of good step-up rings to adapt from (58-67mm, 62-67mm, 72-82mm, 77-82mm, etc)