Skylight filters and UV filters are not the same. Skylight filters are intended for use on color film and have a very mild pink/magenta tint to make photos shot outdoors under natural light look more natural/color accurate, while UV filters are completely clear. I keep a UV filter on all of my lenses (unless using another more specialized filter) to keep out dust. I don't recall ever noticing any difference from using a UV filter on a digital camera, but it has been a LONG time since I've done any kind of side-by-side testing. Recently, however, I accidentally used a skylight filter on my digital camera thinking it was a UV filter. It gave the photos a very noticeable magenta tint that was difficult to correct in post. (I'm not very skilled or experienced with digital image manipulation, so YMMV.)