I've previously written about why I like to keep a filter on the front of each lens to protect it (normally a UV filter). It is a subject that seems to divide photographers - some always have a UV filter on each lens, while others don't like to put any extra glass between their lens and the subject matter.

While recently in Europe, I had another experience that confirms why I have a filter on each lens.



While getting down on my knees to shoot some interesting cobblestones in the Netherlands last month, I stumbled, and the end of my lens banged into the hard cobblestones. I had the Canon EF-S 10-22mm wide-angle lens on my camera at the time, with a 77mm low-profile circular polarising filter (CPL) on the lens.

The end of the filter took the brunt of the impact, as shown in the photo below.

damaged CPL filter on a Canon EF-S 10-22mm lens

The lens itself wasn't damaged at all, other than a slight scuff mark on the outside of the filter thread. Despite the damage to the CPL filter's outer element, the filter glass is still intact, and the filter still rotates fine (initially a little stiff, but it has since loosened up).

damaged CPL filter

With the damage to the CPL filter, I can no longer attach another filter to the front of this CPL filter. However, I don't like to stack filters, so that's not an issue for me.



If I hadn't had any filter on the lens when it contacted the cobblestones, the filter thread on the lens itself would very likely have been damaged. With damaged filter thread on the lens, I wouldn't be able to screw on any filters, nor would I be able to use my Cokin Z-Pro filter holder on the Canon 10-22mm lens.

I would much rather have a damaged filter, than a damaged lens! A filter is a lot cheaper to replace than repairing or replacing a lens. In this particular incident, although the filter was damaged, it's still completely useable.