Ouch !!

There are many different opinions on whether a UV / skylight or any sort of protection filter is required on your lens, and whether one reduces the clarity & performance of your expensive piece of glass. Well that last point is a good reason to consider one at least, as it can well be the difference between replacing the filter versus replacing the lens or at the very least an expensive repair to the lens's front element. I personally haven't found there to be any degradation to my images  - all my lenses are fitted with a UV filter. I would recommend buying the best you can afford though as some of the cheap ones will definitely lower the image quality from what I have seen. I am definitely careful with my gear, and have had a pretty good run over the years but twice now a lens has been saved by that UV filter. The last incident involved my camera body with 24-70 lens attached falling from a back pack that wasn't zipped up properly onto a tiled floor (from over a metre). The lens hit first followed by a very loud noise and the distinct sound of glass smashing. This was followed by a string of naughty words from me along with a small coronary. After the smoke had cleared and I calmed down I discovered the filter had sacrificed itself and the lens had only a  minor battle scar around the end of the barrel - I have tested it thoroughly since and it hasn't missed a beat. I am most certainly counting my lucky stars but I think it is also testament to the build quality and toughness of the true pro gear - it is big and heavy for a reason, and not just to put your spine out of whack. That $50 filter saved me $2000+.

 this is the filter's outer ring after I  persuaded it to part company with my lens.