UPDATE: 20/5/2009 filter comparison link added

We have all been recommended to buy UV filters by those salespeople, whether it is a Hoya, Cokin or the like, or even the high end Nikon, B+W, Tiffen, do we need them? Then there are ‘creative’ filters with exotic colour tones and graduation, do we need these?

In short, this should be a decision that you make for yourself, BUT there are a few arguments for both sides of this debate.

Pros

  • Scratching or damaging a filter is cheaper to replace than damaging the front element of your lens. Even the cheapest of lenses will cost more than a decent filter
  • Filters allow you to: change exposure, change colours/colour balance, increase/decrease contrast, add a visual effect

Cons

  • A lens is carefully designed and coatings are very carefully researched as not to affect the performance and colour rendition of a lens, a filter will affect this performance
  • Adding filters can lead to vignetting (light fall off in the corners)

Thom Hogan has a really good article about filters for those who want to read more. Here is an excerpt from a larger article by Thom that has a bit on his thoughts on filters.

Filters are for koi ponds, Sean. I’ve never been a huge fan of filters, but digital has turned me 100% against them unless they provide an effect I can’t get any other way. That means that the most used filter in my bag has turned from the graduated neutral density filter I almost always had to use with landscapes to hold dynamic range with slide film to the Singh-Ray Variable ND filter I use pretty much only with moving water. What’s the problem, you ask? Loss of contrast and back flare. The AA filter that sits in front of the sensor on a digital camera is flat and highly reflective. So more light bounces back into the lens than it did with film. And some of that has a tendency to bounce right back to the sensor if it hits a flat piece of glass anywhere forward of the sensor, i.e., on a filter. Indeed, Nikon changed the design of the protective glass on their exotic telephotos for this very reason; it used to be flat, now it has a slight curve to it. They’ve also changed to back-coating on some rear elements to lower the potential for problems. Basically, what I see is this: filters lower my overall contrast and increase the likelihood of fringe flare on high contrast edges. So, I’ll use a filter when it’s necessary to get the pixels I want, but otherwise I leave it off. ~ Thom Hogan

Another good article to read on filters can be found here, where they have compared a large number of UV filters to see if they are worth the cost.