It has been debated in the past whether using a UV Protective filter on your lenses is a good idea. If it actually improves image quality or adversely effects it is also a point of debate. I for one had used them in the past full-time on my lenses but have experimented with them on and off to check IQ. I have not seen any noticeable difference with or without. Last night, my camera bag slipped from my hand and dropped to the asphalt. Slight thud and scrape, nothing to worry about. I thought nothing of it since the drop was like 18" at most. I have a Kata H-12 Sling bag and it is built like a tank. Dropped it before with no problems. Went to do a birthday party today and removed the lens cap from my 24-105 f/4L IS only to see shattered glass. Needless to say my heart skipped a beat. a loud, WTF was more like it. At first i thought the lens was toast because I had removed the filters off all of my lenses a few weeks back. A closer look revealed a filter ring on the lens. Sigh of relief to say the least. After carefully removing all of the shards, the lens was intact. As light of a drop as I thought it was, the protective UV filter did the job and absorbed what force there was in the drop and saved the lens. Not sure if it was designed for that, more dust and debris i suppose, but thank goodness I had it on. Granted it was a $80 Hoya Pro1 filter, better than the repair bill of a few hundred and loss time with the lens. Gonna run more test with the focus chart to make sure everything is kosher, but one thing is for sure...filters are going back on. Just thought I would share this experience for anyone who might be on the fence regarding the use of filters.