Hi guys, I've been taking quite a lot of landscapes lately and I really thought the use of some ND filters might help in improving exposures and increasing DOF. The question is, I have yet to purchase a really wide lens and hence have yet to really settled on a fixed lens diameter. I was considering between the cokin square type or the common screw on filters. Which type of filters normally give better results and have more versatility? I'm very new to such filters and hope some gurus out here can advice me on which type is more suitable. Thanks!!!