Lens Filter

[Tailgunner9]

Which filter should you use on Canon 17-85 lens EF-S A polarizer or UV

[another view]

Usually you'd only want a Polarizer when you want that effect - it will cost you a stop or two of light depending on the situation and angle that you're at to the light. A lot of people use UV filters as "protective" filters on their lenses because they're clear. Make sure to get a good multi-coated filter; Hoya HMC have worked well for me.

However, a lot of people - myself included - don't use any filters on a regular basis. I almost always use a lens hood which will provide some protection to the lens as well (assuming it's hard platic or metal). The downside of UV filters is that they can flare just like a lens can and are usually more likely to do it. A hood is designed to cut lens flare, so there is really two advantages to using a hood. Get the hood that's specifically designed for that lens; it will give you the most protection on both accounts.

[mwfanelli]

Which filter should you use on Canon 17-85 lens EF-S A polarizer or UV

A polarizer is not a full time filter. It cuts light down by 2 - 2.5 stops. Use only when required. By the way, you need a circular polarizer, not a linear.

The UV filter is useless. If you insist on one for "protection", get the very best you can afford.to limit the image degradation. A better solution is to use the free lens cap. A hood is also great as it does protect the lens as well as reducing flare and stray light.