I see the question asked a lot. Should I get a UV filter to prevent my (expensive) lens from being damaged should something bad happen? Or “the salesperson told me I’d get better photos if I used a UV filter.”

In a nutshell my answers are no and wrong.  The thinking that a $25, $50 or $150 piece of glass in front of a $1,000 lens is going to somehow protect the lens element from harm seems a bit absurd except in a very few scenarios which I’ll address in a moment.  Moreover, to assume that a thousand dollar lens’ image quality will be improved by a filter is unlikely.

Here are some of the arguments for NOT using a filter (clear, UV or any other for that matter).

1. A filter creates another surface that may cause additional flare, glare or reflection.
2. For all but the most perfectly polished and coated filters, optical degradation is certain with a filter.
3. Filters can introduce color casts and vignetting.
4. Putting a thinner shatterable piece of glass in front of a lens provides a source of sharp shards with which to to scratch the front lens element.
5. Those who leave a filter on all the time often find their protection becomes unremovable preventing them from using a more useful filter like a polarizer or neutral density filter.

But… That Filter Might Save My Bacon!

Think about it. In what scenario will a filter protect the lens? A blow by a golf ball, baseball or softball? Nah, a direct blow will shatter the filter and drive shards of glass into the front element.  A drop onto the floor, lens first? Maybe. The filter holder may provide a little extra protection to the lens barrel, but again, when the glass filter shatters you’ve got shards of sharp up against your expensive glass.  What about a fall onto a rock?  Yep, a filter might help a little, but a lens hood would help a lot more – as would a lens cap.

Block UV rays

What about the argument that a UV filter will “block UV rays” and improve the contrast and exposure?  That is part true – if you’re shooting film. DSLRs are far less sensitive to UV light than film and that filter is more likely to become a source of glare, flare, internal reflection and vignetting.  That UV filter is also yet another expense and item to carry around.

When Does it Make Sense to use a UV/Clear Filter?

If you have burning metal or corrosive substances flying at your camera, I would certainly prefer that they strike a cheap(ish) piece of replaceable glass rather than my expensive lens. Also, some lenses are only well sealed against rain and dust if you put a filter on them. So an excessively wet, dusty or sandy environment might be a good candidate for filter use.

What Do I Do to Protect My Lens?

Aside from being careful, I would argue that using a lens hood is an almost ideal solution. A lens hood helps keep things away from the front element and it also serves the important additional photographically USEFUL function of keeping off-axis light out of your shot. Off-axis light can cause significant glare and flare and attendant loss of contrast.  Even the best filters are little or no help with off-axis light.

My personal policy is also to “cap the lens” whenever  I am not shooting and definitely before I move anywhere. The cap stays accessible in my back pocket and it goes on the camera before I move it. Much like my seatbelt is always fastened before I start the car.