There are times when a UV filter is a good thing. Like when you're hiking at a high altitude or taking pics at the beach or in the snow. It does cut some of the bad reflective light from white surfaces and when you are somewhere up high. It can also help with sand and grit when the wind is blowing but you must be using a good one, not a crap one, and it does mean adjusting your exposure et all a bit to compensate.
Think of a UV filter as a light pair of sunglasses for your camera. Sometimes it does help to have sun glasses on in the brightest light or when stray light is bouncing around all over the place, but sometimes having shades on can get in your way of seeing well too. You'd maybe take off the shades when you walk a bit more into shade, no? A polarizer that's just like using polarized sunglasses on the water or around snow. There you need that to cut the glare, but you don't really need them on an overcast day.
But no, you don't need to leave one all the time. That's just a sales person trying to sell you a filter. There are legit uses for one though and I do keep one in my bag along with my polarizer. Where I live actually there is a lot of reflected glare. You don't go out the door sans sunglasses for long if you don't want to end up frying your eyes. Sunscreen is kind of mandatory too. Using a lens hood/UV/polarizer combo can actually be quite necessary at times.
I live in the tropics. Too much UV can be hard on me and my eyes. I'm thinking maybe a bit eventually on lens coatings too maybe. My very dark coated sunglasses tend to actually fade in a year or so actually just from me being outside a little. So it makes sense to me that my lens coatings might too eventually. It really depends upon your location I think. But most places, no, it's not necessary, not unless you happen to shoot mostly at the beach or up a snowy mountain and rather constantly besides....
I don't believe UV filters are just useless though. I've seen the effects of long term UV exposure on my glasses coatings and it really made me think about my lenses and UV. If my sunglasses can go from ultimate dark to pale gray in a year just going in and out of stores and such and shooting only randomly outside then maybe a UV filter on the lens part of the time isn't such a silly idea. The UV stuff on my car windows, same thing. I had to have it darkened again this year but like I said, tropics, more near the equator, blah, blah.
I can get fried in 10 mins standing outside sans my hat and sunscreen but likely my lenses are a bit less likely to damage than redheaded, fair skinned, little me...I do wonder sometimes though, seeing the sunglasses and how they fade. Some UV exposure is necessary though for lenses. Keeps the fungus critters away....
Last edited by magkelly; 11-08-2012 at 09:47 PM.