anisotropic filtering

[Gawain of Orkeny]

OK what does it do and what are the advantages of turning it on and off?

[Bijo]

It shows better quality textures in the distance, better filtering of textures and such. For instance, when not using it the textures look vague in the distance, but when you apply it, they look sharper.

[LeftEyeNine]

Not a great impact as anti-aliasing can do. Bijo defined it quite right. So it depends on the pay off between your preferences for an indirect visual effect, something generally out of your focus, and system load.

[Husar]

Well, it depends, in some games the textures look really washed unless you turn on AF. But I almost never use the highest setting because at a certain distance, the difference is hardly noticeable anymore but the fps drop usually is.
Though IIRC the newer your graphicscard, the less your fps will drop, the 8800 series can do it with a very low fps drop IIRC.

[Productivity]

This gives a decent summary, the examples on the next page put it into a real perspective though.

[sapi]

You should be running at least 4x depending on your video card, imo - it really makes a difference