Using filters to protect your lenses
This, ladies and gentlemen, is why using a UV filter on your lens is a good idea. Usually. Some times.
The strange thing is, I have NO idea when this happened during a shoot at a reception venue where I was doing room shots and detail shots. Most of the times I was using two cameras, with the other one slung over my shoulder. At some point I lifted the camera to my eye and noticed rainbow colored diffraction patterns across the image. My immediate reaction was .. huh? My lens is THAT dirty? And then I checked and saw the actual damage.
Whatever caused that impact would’ve destroyed the front element of my lens, so the filter saved me a lot of money there by protecting my lens. (Even then, the filter cost around $110 .. ouch!) Btw, this was with the lens hood in place.
The downside to using a UV filter as a permanent fixture on a lens, is that you risk flare and ghosting whenever the light is coming from the front. A lens hood doesn’t cover all that much when you’re using a wide zoom. A poor grade filter will also lower the contrast of your images.
There is no definitive answer to the endless discussions about the pros and cons of using a UV filter (or similar) in front of a lens – it’s a good idea sometimes, and sometimes it isn’t a good idea. Personally, I use high quality UV filters on all my lenses, but I often have to remove the filter when I am shooting into a light source or suspect I am getting flare. But that’s the beauty of a filter – you can always take it off momentarily if you need to.