Never in my life did I expect to see so much debate over something as simple as a filter, but if you pardon the pun, the argument over whether or not a UV filter is necessary has become quite the polarizing topic. Back in the day, a UV filter served the purpose of preventing UV light from exposing film and causing a haze to appear in the image. THe image above was made using Fuji Velvia film and a UV haze filter. However, with digital cameras, there is already a UV/IR filter over the sensor that eleminates haze from a scene.
So the question is whether there is still a need for a UV filter with digital photography. There are two schools of thought on the matter. The first being that a UV filter is a low cost way to protect the front element of the lens from dust and scratches, and the other being that adding another piece of glass will only offer minimal protection at the cost of reducing image quality.
My opinion definitely falls in to the latter of the two categories, and here is why. A cheap poor quality UV filter will hurt the overall quality of an image. Sure, a $50 UV filter might seem like a good way to protect a $1,300 lens, but just like a chain is only as strong as its weakest link, a lens is only as good as its cheapest element. What’s the point of even having a nice lens if you are going to stick a cheap filter on it, that will lower quality and increase lens flare The alternative is to purchase a high quality UV filter like the B+W UV coated filter, available for $190 from B&H Photo. Of course the downside here is that, it would cost $1,900 to put a UV filter on all of my lenses.
How important is it to even worry about protecting your lens? I use only Canon ‘L’ series lenses. All of them have a very tough fluorite coating on the front of the lens which is pretty difficult to scratch. That isn’t to say I have never scratched a lens, but how will a small scratch in the lens effect an image? With longer zooms, a scratch will be almost unnoticeable, because the minimum focusing distance might be several feet in front of the lens. With wider lenses, a scratch or dust can definitely be a problem. To satisfy my curiosity, I called Canon to ask them how much it would cost to replace the front element of a lens, and they told me $200-$400. That is not much more than the cost of replacing a UV filter. Another factor to consider is that a serious accident that actually breaks the UV filter will likely ruin the front element of your lens as well.
So is that to say that I would never advocate using a UV filter? Not at all. In fact there are times when I do use them. Usually, if I am doing photojournalism, where I know there is going to be a fair chance of material striking my lens like when I spent 6 days in the desert photographing the Primal Quest Adventure Race shown above. During this race I did use a UV filter because I was photographing a lot of the race from in the middle of the action, hanging out the window of a jeep, or running along side the racers.
So whether or not you choose to use them to protect your lens is up to you. You need to factor in the cost of the UV filters, and the cost of repairing a damaged lens. Also you need to decide it the protection they afford is worth the degradation of image quality that will result. My recommendation is to skip the UV filter and make sure you always leave your lens cap on when you are not actively shooting.