Canon USM AF Motor Speed?

[prodigy2k7]

Keep in mind that there are two types of Canon USM. The good (faster) one is called 'ring' USM and is found on higher end lenses. With this type, you can manually adjust the focus with the focus ring, even when the lens is in auto mode...I believe this is called full time manual (FTM).

If you can't override the focus manually, then you probably have the lesser version of USM...which is still better than non-USM but not as good as ring USM.

Another factor that affects AF speed & performance is the max aperture of the lens...bigger is almost always better because it gives the camera more light to work with. I know with the 20D (and probably the 30D) that the centre AF point becomes a more sensitive 'cross type' sensor when using lenses with a max aperture of F2.8 or larger.

I thought that FTM doesnt always mean ring USM,

I have EF 50mm F/1.4 USM and I dont think its ring USM, but it has FTM