For this test a high contrast target is made from a light box and a small slide box lined with black felt. The test setup is photographed with no filter on the lens, a Hoya S-HMC UV filter (a multicoated filter) and a Tiffen Haze 2A filter (an uncoated filter as far as I can tell from Tiffen marketing material). A 70-200/4L lens is used since it is a good constrast lens that has good tolerance for flare. Most importantly I own this lens and happen to have 67mm filters of both types available. For each condition three shots were taken to verify there was no shot to shot variance. Only one of each is shown here.

So here we have the 70mm/4.0 shot with no filter. The average RGB value of the center of the dark box is 53,51,46. This is the base contrast level for this lens at this exposure. For those who care these were all shot in sRGB with daylight WB and parameter 2 set on the XT (that is, contrast, saturation and sharpening at 0).

This is with the Hoya S-HMC UV filter, the RGB is 54,52,47. This is a negligibly lighter tone than without the filter, but for what it is worth we can say we lost a smidgen of contrast. One would be hard pressed to see the difference.

This is the Tiffen Haze 2A filter. Let no one ever say coatings don't matter. Yikes, there is a clearly visible difference here. The RGB value is 96,93,80. This shows an uncoated filter causes significant loss of contrast compared to no filter or a multicoated filter.

Just for variety the same test was done at 200/4.0. Here, with no filter, the average RGB value of the center of the dark box is 41,41,37. Again this is the base contrast of the lens for this target. This seems to indicate the lens is a bit more contrasty at the long end, but perhaps this is also because the lightbox doesn't quite fill the frame as much as in the 70mm shots.

With the Hoya S-HMC we get 46,44,39. Now we see a more measurable difference between no filter and the multi-coated, perhaps because the lens has more contrast to start with at this focal length. Probably not a very noticable difference in all but the strongest contra-light situations (like this contrived one), but nonetheless there is a difference.

Well the Tiffen isn't doing so well still. Obviously a big loss of contrast. RGB is 78,77,68.

Just for giggles the light box was turned off and the identical exposure taken (no filter if it matters) and a RGB value of 0,0,0 is obtained.

Now it was time to test some flare. A halogen desk lamp was set just outside the field of view (you'll see it better in later shots) and once again a series of exposures were taken. These were all done at 200/4.0. It is a bit harder to get a read on the central RGB value since the flare varies over the dark box. These measures should probably be taken as plus or minus a count. Here, with no filter, we get 156,82,46. This is just the reference value for flare for this particular situation with this lens.

Visibly the Hoya S-HMC does suffer a bit more flare in this drastic situation. The RGB value here is 165,90,50. Certainly noticeable but by no means objectionable, especially considering the severity of the test.

My, does the Tiffen suck up a storm here. RGB value is really hard to pick because of the severe flare across the dark box, but picking the center the same as on the other two shots the RGB is 237,166,101. Ouch.