Here are the results of the 200mm contrast test side by side. The 200mm test was choosen since it appeared to have the largest difference between the no filter and multicoated filter cases. I'm interpreting this as the 70-200 having a bit more contrast to start with out at 200, but I could be wrong. It is worth noting that in the 70mm case it is impossible to distinguish the no filter and Hoya S-HMC filter squares.
It appears that in very strong contra-light and flare situations that a good multi-coated UV filter holds up pretty darn well. It does in fact cause a bit of loss of contrast, but nothing awful. In a more normal day to day shot without a strong contra light source there'd be no noticable difference. An uncoated filter on the other hand is an abomination if bright light gets near it.
Similarly for polarizers coatings really are a good idea. Sorry to say I think we'll just have to pay for performance.
What does this mean for me? It means my Hoya S-HMC UV filters are staying on my glass. For all but the most extreme cases they have no apparent impact on flare or contrast. I'll probably take them off in the rare cases I'm dealing with a serious contrast issue but most of the time they'll stay on keeping the dust out and, in not too long for me, salt laden marine iguana sneezes off the front optic.
In addition I'll be trying no filter/S-HMC filter comparisons of real world shots as I come upon them.
Others have reported some AF issues with UV filters. I've yet to experience but will be on the look out.
If you'd like to read Hoya's marketing-speak about their coatings you can go here
. Remember, in this test both Hoya filters were Super HMC filters.
I had some issue verifying that the Tiffen filters were in fact uncoated (as opposed to single coated). I'm leaning towards uncoated since no where could I find Tiffen making claims on any coating at all and I'm sure they'd take the opportunity to point them out if they had them. In addition a FAQ on the B&H website specifically refers to the Tiffen filters as uncoated.
What about other brands? Well I'd expect high quality multicoated filters in general to perform similarly. Of course there is more to a filter than just its coatings (e.g. construction and color shifts) and many people have religous affinities for various brands. I'm not plugging Hoya here, I just happened to like their price point for a good multi-coated filter.
As far as the Hoya HMC filters (that is not "super") go I don't have any to test, but based on the Hoya marketing babble I'd expect them to be superior to the uncoated by a wide margin and perhaps a little worse than the Super's just based on their slightly higher reflection numbers.
Hopefully you've found this helpful.