I am a little mystified by the various filter systems used for large format. I have never actually seen anyone use a filter that did not simply screw onto the lens, but I know, from this site, that there are systems which adapt to any lens. I also read that some filter systems work in front of the lens, others behind. Can any of you give me some tips on what to look for in a filter system? Robert White in the UK has quite a bit on Lee filters. Any others worthy of note?

I shoot mostly black and white, in 4x5 on a Wisner, and 5x7/8x10 on an old Ansco. I would like to get something that works for all