panning shots

assuming you use autofocus, do you keep the autofocus working while panning shots ? or does that depend on the camera ? my Canon USM lens is supposed to have a pretty quick autofocus.
Or should I focus on the car when i see it then just follow it through with the focus set ?

thanks for any advice.

On the EOS 30 make sure it's set to AI Servo. If you are using the Sports pre-set this is already done for you. Half-press the shutter as the car approaches and keep it held down. The camera will adjust the focus as necessary until you fully depress the button.

You might have a slight problem if you are very close to the car or it's travelling very quickly but in general the EOS should have no problems keeping up.

right, ok thanks.
I remember when i last used it, i was keeping the autofocus pressed.

It works nicely with AI servo (eos 50 here) if you take 1 shot per panning. But if you take multiple shots you'll find that 4 frames per second much reduced (and what's more annoying is that the camera actually fires when it decides that's the right time) I usually use Autofocus, but 1-shot setting. Or prefocus the area and use manual focus.

I manually focus on panning shots as my Canon and the aftermarket lens just are not fast enough. The camera does not have predictive focus. After some practice I have gotten pretty good at focus tracking fast moving race cars.