This is one of the biggest topics of debate when it comes to photography and lenses. Should you use a UV filter on your dslr? Well some big photographers do not. Some do. Here is my experience and opinions on when you should or should not use them.
Reasons to use UV Filters
IMPORTANT UPDATE: Some lenses when zooming, like the Canon 16-35mm f2.8L II, the front element slides in and out. This creates a suction that will pull any dust and debris into your lens. You must use a UV filter on a lens like this to seal it from dust and keep it as clean as possible or else you will find your lens unusable after a few years. This has happened to me. After several shoots in dusty desert conditions my lens has so much dust inside it no longer is usable at high apertures and I have to send it into Canon for disassemble and repair. Use a UV filter on your zoom lens if the front element moves in and out!
A Little About UV Filters
UV filters are suppose to cut down UV light, but really modern lenses and sensors now have advanced coatings on them so it's no longer necessary to add extra filters for UV light. They were really more designed to be used with Film.
Now, the main reason to use a UV filter is to protect your lens. And this is true in more than one way. First and most obvious, it's nice to have them incase you accidently bump your lens on something breaking your cheap UV filter instead of chipping the front element of your lens. This is even more important when you have expensive lenses.
UV filters are also used to weather seal your lenses. A lot of Canon or Pro lenses are weather sealed, but not completely until a filter is screwed onto the front. So if you're shooting near water falls, in the rain, on a boat or anywhere that might have weather problems, you might want this extra protection.
UV filters aren't just used to protect your lens from physical damage but also can be used to keep them clean. Here is an example. I was shooting the Santa Monica pier one night when the waves were about three to four feet. It was throwing up a salty mist that would collect on my dslr and my lens creating a sticky film. When I tried to wipe this film off it would smear everywhere. Then it gets on your micro fiber cloth and you have to keep using clean cloths to try to get it off, in my case the inside of my shirt. Luckily I had a few filters so I could just swap them out and put on a new one instead of having to clean the existing one. The last thing you want to do during a sunset is waist vital minutes cleaning lenses and filters.
Other lenses like the new Canon 40mm pancake lens also can be difficult to clean. The lens is set into the body making it easy for edges to collect a lot of dirt and dust which are hard to get out. If you have a UV filter on, then you only have to clean a large broad piece of glass.
Reasons not to use UV Filters
There are a few reason photographers stay away from UV filters. They can increase the flaring on your lens. Especially if the filter isn't coated very well. If you get a UV filter make sure you get one that is multi-coated. This helps get rid of the flair and reflection.
There is an interesting article I read on lenses and coatings. You should check it out at CanonRumors All About Lens Coatings if you want to know more. To summarize; glass reflects some light, so the more glass you add on your lens the less light gets to your sensor, like 4%-1.5%. The advanced multi coatings keep light from reflecting allowing more light to pass through the lens resulting in a higher contrast image. So an advanced coating, multicoated both sides will only reflect 0.5% of the light.
On some lenses like my Canon 70-200mm f2.8L USM IS II, adding a UV filter can cause more vignetting. In this case you might have to get a Slim UV filter which are harder to find can can cost more money.
Some say a lens hood can provide all the protection you need from physical damage. And this is true. On many lenses I use, the hood is so massive that there is really no reason you'd ever have to worry about something hitting the front element.
In a studio environment it really doesn't make any sense to use a UV filter. You don't have to worry about the weather or UV light and the flaring from poorly coated cheap UV filters could create extra problems with the studio lights. But beware of dust.
Do you need a UV filter?
Well, It's up to you. I use them sometimes because I am a run and gun type of photographer. I throw my lenses in my camera bag without lens caps. I always am shooting near the beach or water falls or in the rain. So for me, it just makes sense in those situations. When I shot in Death Valley or the desert I did not use one. (lesson learned, dust!) Now if I was strictly a studio photographer, I would never use one.
What kind of Filter should I buy?
I've heard so many photographers say, "If you spend all this money on your lens you better get a good UV filter to protect it and not some cheap one." The world of making filters is a lot like the sunglasses industry. A lot of times you're just spending the money on the brand name.
There are companies that sell you them for $150 dollars, and some that sell you them for $20 dollars. I've had them all and honestly, as long as they are multicoated I can't tell the difference. Putting something over your lens won't really change the clarity or sharpness of your image by much, like said above 4%-0.5%. That comes from the engineering of the fluorite and glass elements and coatings inside your lens.
I have one really expensive B+W UV filter, but lately, I've started buying the cheaper ones off Amazon. Like Tiffen, and Hoya. I like Tiffen.
Here is what I currently use if you're interested in checking it out.
So should you use a UV filter on your dslr? It's up to you. If you have a lot of money and don't care about having to replace your lenses for the small chance something happens to them, then don't get one. I've been using my filters for years and they are all still in mint condition. Not a scratch. So it's safe to say I didn't need them for protection. I just like to use them because they are easier to clean, but lately for my landscapes I've hardly taken them out of my bag. Except when I'm at the beach.
Also be sure to check out this video by DigitalRev UV Filter vs No UV Filter. They talk all about UV filters and I agree with this video 100%. It's a really good video as always.
And the guys over at Lens Rentals posted a pretty interesting situation you should really be careful in, especilaly without a UV filter. A fun read. How to ruin your gear in five minutes.