I've always wanted to know, and haven't been able to find out why the anisotropic filtering setting only goes up to 15x. I couldn't find anything on the forums or google, and I've just been curious ever since Fallout 3. All other games allow up to 16x, I just want to know why Fallout only goes to 15x.

I just checked to confirm this and noticed how weird it was.

Don't worry about it, though. 15x and 16x should be almost indistinguishable.

Mystery! You could force it to 16x with an external program though.

I use Nvidia Control Panel to force it.
It just feels so... uneven to me! Lets call it OCD lol.