Over the past years I've mainly shot with some sort of filter on most of my lens, mostly to prevent the front element from getting scratched. I learned the hard way once, when a lens that had no filter on, my Sigma 10-20mm f4-5.6, made solid contact with a door handle on the front element as I was rushing out of our hotel room in Spain. This incident left a permanent mark, more of a coating mark than a scratch, and while it didn't at all affect lens performance, it did affect its resale.
However, much has been made about the reduced sharpness and performance of lenses with filters fitted, so lately I have been shooting my new Sigma lenses without filters, but instead regularly fitting the lens hood. These lenses have taken some of my best photos in a while, with excellent sharpness, so there maybe something is to be said. It also could be suggested that lens manufacturers don't design their lenses with filters in mind, and extra optics, ie the filter, may cause a deterioration n quality.
On the negative side to that argument, I had been using a crappy filter on my Tamron 24-135mm f3.5-5.6 zoom lens, yet it can still out resolve the D600 sensor at f8. The same can be said about both the Sigma lenses on the NEX5n. Weird. The jury is still out, but I have decided that it I can get away with not using a filter and still offer some protection for the front lens element, then I probably will.
|Fuji X100 with old, crappy Toshiba 49mm UV filter fitted|