Gearing up for a summer vacation trip to Yellowstone and southern Utah, I have my trusty EOS 5D + 24-105 and I've just taken delivery of the Canon 100-400 mm IS USM. I'm itching to go out and play with it but I won't risk it until I get some protection on the front of the lens.
Question is, which protection?
I wan't something I can leave on the lens all the time which - ideally - will serve some optical purposes as well as a mechanical role. I don't want to be constantly switching filters. And anyway the front of the 100-400 is 77mm, which means that filters tend to be pricey.
What sort of filter would meet my needs?
I've taken about 100,000 images with my 100-400, over a period of 3 years, and have never had any filter on it except a rare polarizing filter (for shooting fish in lakes, etc) and the occasional color filter for special purposes. I don't have a single nick or scratch or abrasion on the lens, nor any of my other lenses.
Protection filters are not necessary, IMO, unless you're going to be in windstorms, or are photographing cars racing on gravel, and things of that nature. The lens hood will provide all the protection you need from the lens falling or bumping into things, IMO.
Filters just put out something closer to where the sun can reach, to lessen contrast by the fingerprints and dust lighting up from the sun, and they lose some optical sharpness (though that varies with quality). With very wide angle lenses, the dirt on filters can actually be almost in focus.