OK, welcome back. So - what are some of the things you need to think about when shooting high speed subjects like runners and skiers? I'll talk about this photo to illustrate what I mean.
The first thing to realise is that you are going to need to explain what you want to your model. Believe it or not, getting a skier passing through the sun with a giant spray of powder doesn't just happen by accident. Explain exactly the path you want your model to take, including which way they are going to turn, where you want the powder spray to go, what body position you want - everything you need in the final picture.
This is especially important for ski photography for two reasons: firstly you only get one try before you get tracks through that beautiful patch of powder you were counting on and secondly its hard (sometimes impossible) to hike back up the hill to take the shot a second time.
To communicate effectively make sure you pack 2-way radios, or at a pinch mobile phones. Sometimes your model will have to start their run from far uphill, or even out of sight, and shouting just won't cut it. Trust me.
Once you've got everything lined up you need to get the shot. There are a couple of ways you can go about capturing high speed subjects. OK, actually there are 3, but I'm saving one of them for another post. Which you use depends on the type of shot you need to capture. There's the 'static' method and the 'panning' method. I'll start with panning.
The Panning Method:
1) Switch your camera to 'tracking' autofocus. On Canon cameras this is called AI Servo.
2) Start your model off on their run
3) Find the model in your viewfinder and allow the autofocus to lock on
4) As the model reaches peak action, hold down the shutter button with the motor drive screaming
5) Hope you got the shot
The advantage of this method is that it is relatively easy. The tracking autofocus on high end Canon and Nikon bodies is now exceptionally good, and once it has picked up your subject, 90% of the subsequent frames will be in sharp focus. Secondly, you can follow your subject through the viewfinder and shoot when the action is at it's peak - at the centre of the turn or in the middle of a stride.
However you pay a price for it being easy. Firstly, the autofocus sensors, even on top-end cameras, are clustered around the centre of the frame, making it impossible to have your subject far off center. Secondly, because you are tracking the subject not the background, it can be hard to get the background framed the way you want.
So if you're finding these limiting you can try another way: the Static Method. This allows you to have off centre subjects and frame your background accurately, but requires you - and your model - to have very good timing. It works best when shooting very close to your subject with a wide-angle lens.
The Static Method:
1) Frame the background you want in the viewfinder.
2) Focus on the point where you want the model to be in the picture
3) Switch to manual focus - either disengage autofocus from the shutter button (CFn 4-1 on Canon) or switch the lens to manual
4) Keep the camera framed on your background and have your model start his run. It can be helpful to have your assistant count down their approach so you are ready
5) As the model passes into the correct point of the frame, shoot
As you can see, this requires you to have very good timing on the shutter, and for your model to hit his mark precisely. To maximise your chances it helps to shoot with a high resolution camera and frame the shot a little loose, giving you room and resolution to crop in post. Also, to ensure critical focus, close your aperture down to give you more leeway with the depth of field.
It's hard, but when you get it right it gives you results that can't be had any other way.