Matthew Saville, over at SLR Lounge on YouTube, recently set out to bust (or confirm) photo myths and stereotypes, and his first challenge was this very topic: Do UV filters degrade quality on digital cameras? To test the myth Matthew went out to the mountains armed with his Nikon camera equipment, a tripod, and — of course — a selection of UV filters ranging from cheap to expensive. Then he tested each filter and compared to it to images shot without a filter, and the result?
As Matthew puts it, “UV filters do not horribly affect your images.” But he does note some situation in which you may want to remove the UV filter. The biggest issue he noted, and showed plenty of examples to corroborate, is the negative flare if you are shooting into a light source. As he states, this is not the good kind of flare that adds to the overall look and feel of an image, this is the bad kind of flare, the sort that distracts and takes away from the feel of an image.
So basically, UV filters shouldn’t be a problem so long as you make a point to remove them when shooting into direct light. Matthew also notes that this mostly applies to “high quality” filters, as it is very possible for a low quality filters, such as those that don’t use real glass or otherwise cut corners, to affect the quality of your image. So just make sure to buy quality, reputable UV filters if you do choose to use them.