photo help!?

Hi
just wondering if I've gotten the right technique to take a motion shot wherein the mobile subject is in sharp focus, and the stationary background has speed blur:

I tried to take a few shots the other day like this, and, shooting with cheap 400ISO 35mm in the pentax, I set the speed to Bulb, followed the subject while depressing the shutter button for a second, trying to keep it exactly in the same spot in the frame, then released.
I'll find out in a week or two if I got it right when I finish the roll off and develop the roll, but I'm wondering if I'm doing it right?

You don't need to use bulb for it. You'll get the whole picture blurry that way. Just set the shutter speed to like 1/250, use the same technique you were describing, but release the shutter while you are panning.

Right. The chances you'll get the subject in focus while panning on bulb for one second are super rare. Set the exposure correctly, but do it with a smaller aperture and a longer shutter duration; for instance if you wanted a good crisp stop motion, you might do 1/1000s at f3.5. To show blurry motion, you might use 1/125s at f11. Same light gets through, but one is blurry.

So, use a slow-ish shutter and tight aperture. Pan with the subject and shoot.

It doesn't take much to blur motion. Here is a shot taken at 1/30s while panning. 1/30s is quick enough to keep the subject crisp while panning, but slow enough to blur the background. (not my photo, just googled it)

curtis73 wrote: It doesn't take much to blur motion. Here is a shot taken at 1/30s while panning. 1/30s is quick enough to keep the subject crisp while panning, but slow enough to blur the background. (not my photo, just googled it)

thank you much! I'll post results if I have any favorable ones, when I get the rolls developed

Panning is a skill that demands lots of practice.

I always use shutter priority and let the camera figure out the aperture. For cars on the track I usually start with a shutter speed of 1/250th. This gets the background blurred and the car in focus with the wheels slightly blurred to show the speed/motion.

Shutter speed needs to be varied according to how fast the subject is moving. If the cars are at high speed on a straight I might use a stop or two faster shutter and in slow corners a slower shutter.