It seems that there are many opinions on filters. When I purchased my camera and lenses I bought NC filters for protection for my all of my lenses (all two of them. Ha!) This was from some recommendations that I had read. It made sense to me as I had UV filters on my film camera lenses years ago. I had also read that UV filters were not needed for digital cameras. This info may have been good or bad, but anyway that is what I had read and decided on. I then read in my search for better photos in bright situations that CP-L filters were great. I bought one for each of my lenses (as said before, all two of them. Ha!) Anyway after some time of playing, I have decided to put the NC on my 70-300 and leave the CP-L on my 18-55. Here is my reasoning: The long lens is used mostly for BIF, wildlife photos which can be spur of the moment type photos taken in any direction. The CP-L couldn't be adjusted because of the constant spinning to different directions. Ha! The CP-L does work well on the 18-55 because most of the time I have time to adjust it before taking a shot ie landscape, scenery, etc. Basically I have two lens filters that stay in my camera bag and two that stay on the lenses. Money wasted, maybe or maybe not. For me the jury is still out on it. Ha!
Argue with this. I don't care. Ha! More fun!