I purchased this product as a newbie. I read quite a few reviews and discussions as to whether or not it's needed. I keep it on my 17-55 lens most of the time for protection sake. I honestly can't say that I notice any difference when it's on or off. It is a bit of a hassle taking it off (unscrewing it) and replacing it with another filter. It's not something that happens instantly, so hopefully there's no hurry when you're making the change. Someday I'll have to compare some pics with it on and off to see if there is any difference in sharpness, etc. Get more detail about B+W 77mm UVA (Ultra Violet) Haze MRC Filter #010.