How a UV Filter Can Protect Your Lens

Let's start out with the technical definition:

UV stands for Ultra-Violet, and UV filters are designed to keep Ultra-Violet rays from entering the lens.

Here's a simpler one: a UV filter is a clear piece of glass.

The filter won't alter your photographs: it won't change the colors or make things look blurry.

So what's the point of a clear piece of glass?

An Insurance Policy for Your Lens

The clear UV filter screws onto the front of your lens.

Imagine that you're on a hike and grind the front of your lens against a sharp rock. Without a UV filter in place, you're going to have to replace the lens.

This can cost anywhere from $300 to $3000 (depending upon the lens).

With a UV filter in place, the only thing you've damaged - and need to replace - is the filter. Approximate cost: $30.

Big difference.

What's the Catch?

Since the logic behind a UV filter makes so much sense, why doesn't everyone use them all the time?

Most people do, but there are some professional photographers who argue that a UV filter affects the quality of your photos regardless of the filter's clarity.

This argument also makes sense: for the clearest possible images, don't put something on the front of your lens and leave it there all the time.

In the end, the answer has a lot to do with how you use your camera:

If you enjoy taking your SLR on your travels, hikes and other excursions, where there is a high chance of smacking the front of the lens on something, then always use a UV filter
If you take photos in more controlled environments (indoors, studio, etc.) then you may opt to leave off the UV filter to ensure the highest possible image quality