FILTER ME

[Berter]

looking for some input/recommendations on filter setups. right now i mainly want to get an ND filter but i see myself wanting more in the future. my question is what system do you guys use and which do you find to be easiest to work with and most cost effective- the screw on type with step down rings, or rectangle type with a filter holder? i dont really know much about the rectangle type as i have not seem them in use. i assume you still need adapter rings for different lens sizes? any input will help
Dunca