Lens filter for L sealing

[Leopard Lupus]

Hello there, again!
I am without a doubt sure this has been covered in a forum post before, but for the life of me I am unable to find it.
Last evening I was using my 5D mk ll and 50mm f/1.2 for indoor sports photography, and received wonderful shots. The only issue was the amount of dust in the venue! I have always been opposed to using filters due to placing another chunk of glass on a lens, thus lowering IQ.
My question is: What is the best option for a filter for the soul purpose of weather sealing? I want to be able to worry less about the dust build up on my glass, as well as possible water/sweat from close shots without disruption of the IQ... Too much 
Thanks!

[Edwin Herdman]

If the lens claims a filter is needed to complete sealing, then any protective filter should do.  In that case people usually use the simple ultraviolet filter - I have one and while I don't use it, it doesn't seem to degrade IQ in any notable way.  It probably would protect against fingerprints (not that that's happening anymore...) but seeing what damage a "protective" filter can do to a dropped lens is enough to make me shy away.

[neuroanatomist]

For a dSLR, there's no difference between a clear filter and a UV filter, since the sensor is basically insensitive to UV wavelengths (unlike film). 

The 50mm f/1.2L is one of the lenses that definitely requires a filter to complete the sealing (the other definite ones are the 16-35mm II and the 17-40mm; the ones that definitely do not are the super tele primes; other 'sealed' L lenses, e.g. 70-200 IS, might or might not).

So...UV or clear.  The reason to choose one over the other are cost and availability (in some lines, clear filters are more expensive, and UV filters tend to be more widely available).

Personally, I use B+W MRC UV filters.  The high end Hoya filters (SHMC, HD) are also good.  A cheap filter is a bad idea, IMO.

[lol]

Assuming you don't go for ultra-cheap no-name filters and get some half-decent ones, the quality loss in terms of perceived sharpness from adding a filter is practically undetectable. What can be more detectable is ghosting,  increased glare or flare when shooting into bright lights. So watch out for those.

Personally I use Hoya HD if I need top end protection (thin but toughened glass, easy clean coating), but I also use Hoya HMC UV(C) or HMC UV(O) as a decent quality moderate cost filter. Don't look at the HMC UV(N) though... the sample I tried has a slight colour cast and poorer performing anti-reflection coatings than the others in HMC family and the cost wasn't that much different either.

[JR]

I am using B+W clear and UV filter on my 50mm 1.2L and have been extremely happy with the result.  I see no degradation on IQ what so ever.  As mentionned above other good brand exist as well but I like B+W filters...

[kennykodak]

I am using B+W clear and UV filter on my 50mm 1.2L and have been extremely happy with the result.  I see no degradation on IQ what so ever.  As mentionned above other good brand exist as well but I like B+W filters...

+1

[7enderbender]

In my experience it's worth investing in something like B+W. I'm not even sure if the optical qualities of the better coating really make much of a difference (at least I could not find any differences when using a cheap old Quantaray on my 50 1.4 vs no filter at all). But as far as an extra layer of protection and the quality of the threads it does make a difference.

I first had a chain-store labeled clear filter on my 24-105. I noticed that dust would get through the unsealed edges of the glass during cleaning. Decided to go with the thin version of the clear B+W filter instead. It's a lot more solid all around and their optical qualities are undisputed.

[LuCoOc]

I use Hoya HD UV filters on my Ls. There's no visible reduction in IQ.
Before I went for Hoya I had a cheap Hama UV-filter and it seemed to make my lenses less flare resistant.

Check out this thread:

http://www.canonrumors.com/forum/index.php/topic,823.msg10615.html#msg10615

as well as this very good article @lensrentals.com

http://www.lensrentals.com/blog/2011/06/good-times-with-bad-filters

[Leopard Lupus]

Thank you all for the quick replies!
I will be ordering a 72mm B+W filter today.

[jcns]

make sure you get a multi coated filter.
I once bought a non-multi coated and completely ruined my night shots during a vacation.

[Edwin Herdman]

For a dSLR, there's no difference between a clear filter and a UV filter, since the sensor is basically insensitive to UV wavelengths (unlike film).

I didn't know clear filters were actually produced in volume.  The more you know...