what kind of filter should I buy?

I have a Canon 40D with an EF28-135mm F3.5-5.6 IS USM lens. I am thinking of to get a filter to protect the lens as I take the camera for hiking.

what kind of lens should I buy?

Please give me some advices,

Thanks,

Hi Ping,

The EF28-135mm F3.5-5.6 has a front diameter of 72mm - so that's your first decision made :)

Traditionally most people use a UV filter because it doesn't attenuate light in the visible band, and is relatively inexpensive - and current thinking is that it's best to use a multi-coated filter.

My personaly preference is to use a Heliopan SH-PMC UV filter (B+W filters are also top-shelf), but they're not cheap. Others will no doubt chip in with some lower-priced suggestions.

Hope this helps :)

B+W Pro F series clear UV haze multi-coat or higher end Hoya Pro are also ones I would recommend.

I'd agree that multicoating is far more important for digital sensors than film stock. While previously we might have bought them for basic UV reduction and lens protection, it's beyond me why anyone would add a cheap one of these filters if it may increase your chances of either flare and/or reflections. Now flare & reflections won't always show up, but when they do, it can wreck a good photo.

I'd suggest that if you have really inexpensive lenses now, then it probably (hopefully?) wouldn't cost a huge amount to replace the damaged lens if it was violently smacked in the front: remember, the UV filter doesn't render the lens invulnerable, it just slows down whatever is coming at the lens, so less damage happens to the actual lens. Even with a UV filter, a damaged lens may need repair (and another UV filter!), and it could be almost as inexpensive to replace the lens. On the positive side, it will hopefully help to reduce the haze most of the time, while only some of the time, it might introduce flare or reflections.

If you have pretty costly lenses, when the lighting isn't proper, a cheap UV filter may degrade your good lens' results. If you only could afford to buy the most inexpensive UV filter right now, you might want to defer that purchase until you can afford a slightly better filter. IMHO. They don't have to be too expensive, either. See the bottom link for some highly scoring but not too costly 72mm UV filter brands and makes, and check out their prices on the web or locally to you.

Examples of a Hoya vs Tiffen UV filter in a test:
http://www.kenandchristine.com/gallery/1054387/1

Article on UV filters and how well they block actual UV wavelengths, but remember that the quality of the multicoating (not just its presence) is about as important as the quality of your lens: skimping there could certainly reduce an otherwise excellent lens to bargain bin quality. This comparison never takes any of that into account. Noticeably Tiffen friendly too.
http://photo.net/equipment/filters/

Very nice UV filter comparison (all 72mm UV filters) with sample shots of each:
http://www.lenstip.com/113.4-article...d_summary.html
(note that the far right column of the ranking list indicates the price - possibly not your currency, but at least you can treat the currency as a comparative guage)

HTH,
dlj

This is a well managed and extensive test.

Very nice UV filter comparison (all 72mm UV filters) with sample shots of each:
http://www.lenstip.com/113.4-article...d_summary.html

However at least ten points on each test were awarded regarding UV blocking. This is a non-factor in digital photography since the digital sensor, unlike most films, is not particularly sensitive to UV radiation.

I wonder since the spread between the several front runners is actually quite small, what the ranking would be if the UV blocking factor was not counted in the final grading of each filter.