Serves no purpose that a lens hood doesn't do better, unless it's raining or snowing.

or you are photgraphing at a high altitude where the uv filtration is neccessary.

Every enthusiast photographer, before they can call themselves a photographer, should have to spend some length of time behind the counter of a camera/photo store!

Well, with just a few replies, i notice that no one has said "it protects your lens from damage", yet that is one of the biggest selling points that retailers use to try to sell one. I have not yet taken test photos and then zoomed in to 200% to see what difference there might be, but in my simple mind, the less glass i have between my CCD and the subject, the better, so i'm leaning towards not using a uv filter on my lenses any more unless my "test" shows otherwise. In particular, if i am only 10' away from a subject with a macro 180mm macro lens, i really doubt that many ultra violets can get in the way of my subject anyway.

Arthur, I did as David Brooks said all photogs should; I sold cameras. The UV filter is an "add on" that boosts company profit.
The best arguement that I have ever read against UV filters is in the NYIP course materials. Why are they be,ievable? They do not sell filters!

Ronk,

Well said, I love it. In addition I might also recommend that every photo enthusiast before venturing into a photo store or onto an Internet photo sales site on the web should understand thoroughly what a "spiff" is and some of the effects of the "sales programs" that are imposed on dealers by big companies and distributors and how they influence the behavior of front-line sales personnel.

Well, I've been thoroughly "spiffed" that's for sure.
There are some interesting results if you Google UV filters, such as the following skeptics about the filters:
http://www.photo.net/equipment/filters/
http://dpfwiw.com/filters.htm
http://www.luminous-landscape.com/columns/sm-feb-05.shtml
The long and the short of it seems to be that such filters were probably useful for MUCH older lenses that were both easier to scratch and more inclined to transmit UV rays. Moreover, only the more expensive filters even do what they claim, and even then it depends on the make. Further, with the sorts of myriad-element lenses so common these days (aka zooms) the extra glass of the filter likely degrades the image.
Now my pathetic question, having been talked into expensive multi-coated filters: is there even any basis for this multi-coating? My present hunch, based on a prelimary test of shots with and without (not at altitude) is that the image is marginally better without the filter.

I am leaning towards the side of not using the filters when i take photos, but merely to leave them on at all other times just for the (maybe) protection against scratches. Most of the articles i have read (i didn't want to bias the replies by saying this) state that you should always have a uv filter on your lens in case you drop it. well, duh....if you drop it, it's not likely the uv lens is gonna do that much anyway. I'm thinking i'll do a non-scientific test this weekend using telephoto (up to 500mm), macro (180mm), and a 17-35mm lens, and then compare the images both in RAW and jpeg with some super magnification. My guess is that i probably won't be leaving the uv filters on after this test is concluded. thanks for your insight, everyone...you always have a lot of good information.

Alex,

First of all UV reduction by means of a filter does have a positive functional role, as you indicate at high altitude, but also in certain atmospheric conditions when a lot of moisture content in the air reflects UV radiation in every possible direction creating haze and excessively blue shadows.

Applied to digital cameras how much this UV reduction is needed may be somewhat moot as there is filtration at the front surface of the sensor chip that blocks a lot of UV, and of coarse the mentioned effect of multi-element zoom lenses also probably blocks a lot of UV transmission, especially with different kinds of glass diffraction indexes in various elements..

What makes more practical sense to me is a mild circular type of polarizing filter. From what I have seen of the photography of a professional friend and colleague who uses a polarizer a lot with a Nikon D2X the quality of the color is benefitted quite significantly. But of course that depends in part on what subjects you are photographing and under what conditions - a polarizer is not a universal advantage.

As for protection of the front element, with any prime or premium independent lens I have had my hands on in the last 15-20 years the provided hard plastic lens cap is well designed for protection, much more reliable than a filter and much more convenient than with many older or cheaper lenses.

Coating of lens surfaces has only one optical function and that is to reduce surface refraction of light to enhance transmission. Older lenses for instance without modern coating tend to flare more and do not preserve internal image contrast nearly as well. Applied to a filter there is an advantage as there is to a lens element, but the two simple flat surfaces of a filter do not cause that much potential for refracted light causing a reduction of efficiency in transmission to produce a notable difference except under very close examination if at all.

A protection filter is not likely to affect your images if it's high-quality glass. But buying a cheapo one for a tenner (or even double that) will very likely have an adverse effect. Unless your prepared to pay around

I normally use a multi coated skylight (1a or equivelent) from either B+W or Heliopan because much of my photography is near the ocean and salt air, sand, etc. is deadly on lens coatings. I actually did have one occasion where a filter did save my lens when I fell down an embankment and shattered the filter (yes I did have the lens shade on and it went flying into the surf). The lens itself was not damaged--saved by the filter.

I've never tested it out, but I'm in the lens protection camp myself. While surfing around I found a post(w/pics) of someone that had their brandy new 2 day old 85mm 1.2L II roll out of his bag onto the sidewalk. The filter took all the damage and left the front element intact. Albeit it had to be sent in due to a damaged filter ring, but it came back and immediately had a new filter placed on it.

On a side note, it fell out because his friend was looking through the bag and forgot to zip up while the owner was on the phone in another room.

The moral of the story, always check your zippers to avoid a potential $2,100 accident.

LOL, sorry if I got a bit OT.