i use a uv for each lens as well simply to protect the lens but some just use lens hoods, it 's your call.but i have seen articles where cheap uv filters changed the image quality a lot.
This is a very good point. For a DSLR, if you get a non-coated or single coated filter, it could affect image quality. If you want to use a UV filter for protection, then go for a more expensive multicoated one. I had a single coated one on an adapter for my S1 IS and it caused no difference in quality. I tested it on my K100D and quality was noticibly degraded.
I prefer to use the hood for protection as my biggest worries are from impact instead of scratching and residue. A plastic hood protects from impact better because it can absorb some shock for an impact where a metal hood or filter will simply pass that shockwave on down the lens to the delicate parts inside. Rubber and metal hoods offer some protection, but not as much as plastic. A filter protects from scratches and residue buildup. I typically do not put my camera in extreme situations and opted for just a hood. It would be the best protection to use both, but I do not want to spend the money on a nice filter when the hood should do fine for me in most cases. Plus, my Pentax lenses are known to have some of the best coatings around, so why cover them up?
I also have a CP and a star filter, which I really like. Most film filters have become almost obsolete with software doing the same thing, but there are a few that just cannot be duplicated. For example CPs, neutral density, IR, etc. Other filters can still be more effective, but most people now opt for software solutions for the cost savings, flexibility, and ease of use.
I found an online shop for them that I really like.
http://www.camerafilters.comThey are cheap, seem to be honest, and very quick. They are also a nice place to pick up a few extra caps and so on for next to nothing.
Kevin