content: I bought this filter to protect a Canon EF 85mm/f1.8. It does the job, but I get noticeably better photos with it off. I guess the debate rages over whether a filter to "protect" the lens is even a good idea, but I usually like to have one on, especially if I'm outdoors or in a dustry environment.If you are going to go the "protect the lens" route, I'd recommend something better, like the HMC / multicoated filters from Hoya.