Is AF : 16x supposed to make a 10 fps (measured with fraps) drop over AF : Off or is it just my crappy gpu? (see signature) Not using CCC forced AF, just normal 16x AF through skyrim launcher settings.

Not too much, but it depends on some systems. Here is a benchmark test on AF:
http://www.geforce.com/Optimize/Guides/the-elder-scrolls-v-skyrim-tweak-guide?sf2686171=1

Hope that helps!

That seems too severe...by any chance did you also enable AF elsewhere, like in CCC? That drop seems more in line with AO, not AF hmmm

16 x AF should have 1 or 2 fps impact on Vanilla. If you have any HD texture mods installed though then results may vary.

10FPS is a bit much for a drop, but it could be what it is. Some have gotten better performance setting this in game, some have gotten better performance setting it in CCC. Also, (note I am old and my eyes are not what they used to be) but do you need 16X? For me, 4X is tolerable, 8X is pretty sweet.

Also, if you have this set at 16 in hopes of making the shadows look less jaggy, there are some INI tweaks that are better for shadows.

This would be true for AA, but he is reporting AF. Although the more I think of it, maybe actually meant AA all along. hmmm

6790 shouldn't be experiencing any significant effect in frame rate... at all with x16 applied...

I didn't mean AA, stil talking about AF as in anisotropic filtering. Could it be the drivers, i'm using catalyst 12.2 preview? Also, i have no mods installed and no ini tweaks.

it could be 12.2 related.. but i'm running them on a 5770 1gb at work with skyrim and several super ultra resolution mods with no drop in fps more than 1 or 2 fps going from 0x AF to 16x AF....

You are applying the AF via the Skyrim settings and having set to USE APPLICATION SETTINGS in the CCC?

Yes, everything in CCC is set to default, AF is set to 16x in Skyrim settings, no mods, no ini tweaks, no frame limiters, just fraps, version 1.4.21.0.4., just tried 11.10 catalyst (read somewhere they're good for skyrim) no change, still an exact 10 fps drop (from 59 to 49), I don't know what to do, should I reinstall the game? Does the ingame location make any difference to AF frame drops? I'm looking at a large body of water, and since it looks to me that AF makes more visual difference on water surfaces than on terrain could that be it? Do other graphic setting influence AF? I have AA off, view distance sliders on max, object detail fade off, sky reflections on water off, FXAA on and everything else on high.

water rendering could indeed be the contributing factor..

the way water is rendered....

otherwise general scenery out in variou places would typically have no decernable impact.... i haven't really paid attention to staring at water.

Could you maybe post some screenshots with AF on and off with the frame rate and see?

http://imageshack.us/photo/my-images/837/tesv2012020320583301.jpg/
http://imageshack.us/photo/my-images/38/tesv2012020320572551.jpg/

the 52 fps image is AF x16 and 60 fps image is AF off. I reinstalled skyrim today, no changes, had to overclock my cpu and gpu to get the 52 fps.

Just for grins, try running the game without CCC running. I had some issues with the game that went away when I stopped that program from running.

Well perhaps you've found the 6790's rough spot.... that is a large scene to draw..... and a lot of improvement going from 0 to 16x af for sure..

i think it could be just a weird glitch that may be resolved later with either driver update or game update.. who knows.

considering 52fps though.... it's more than playable.. i personally wouldn't be to worried.

yeah that's a bit high of a frame rate hit just for 16x AF. I only lose about 3fps going from no AF to 16x AF (forced through NVidia control panel with AF=0 in SkyrimPrefs.ini)