Yeah if you buy a filter, spend the extra and get the multi-coated ones.

And i think the 24-105L and 135L needs a filter to complete the seal also. The 17-55 f/2.8 IS needs a filter to prevent sucking in dust.

I personally use Hoya pro1 filters which are reasonably priced and doesn't reduce image quality too much.

I don't know about 24-105L but I have 135L and it is not weather sealed at least not in the same fashion as 24-70L. The 50L and 17-40L need a filter to complete weather sealing because the front element extend and retract inside the barrel while focusing or zooming something the 135L doesn't do. lol the ef-s 17-55 IS would collect dust even with a filter because dust get inside it through the cracks on the lens itself like around the zoom ring etc

Cokin is a good system. Easier to use and also cheaper. especially when using a gnd, you can actually adjust the height. good luck!

This post was edited by SeaBas on Mar 10 2010 12:05pm

all weather sealed lenses need filter to complete the sealing

I've seen those, but I am afraid I will snap the filters in half.

Really? I'll need to recheck my sources.. though i'm fairly positive the longer primes ie 300L, 400L, 500L, 600L, 800L and 1200L are completely sealed without the help of a filter.

@ I've heard tons of great things about cokin filters too from other photographers.

Haha That's why i use the 'Z' type. More tough system with better filters. a little more expensive but better too.

Good info, thanks for link.

i use cokin filters. but i made the mistake of buying Cokin p series when i only had a 52 mm lens. when i bought my 10-20 sigma lens i needed 82mm filters so had to buy a whole new cokin system the z-pro which is dam expensive. cokin filters are really good though but a bit pricey