Background and wheels are blurred, the car is sharp. 100mm, ISO 100, 1/100 sec. The trick here is that you have to move your camera while you take the image. Let’s start at the beginning.
1) Find a good location
The car above was shot at f=100mm. I was about 70m away and 3 meters above the subject. For most subjects you will need a telephoto lens. E.g. if you have a 28-135 or 70-300 you will fine.
2) Take your time
Besides a good technique, this requires a bit of luck. When you start you will have less than 10% keepers. So shoot a lot when trying this for the first time and also try different shutter speeds …
3) Camera settings
AI Servo (continuous focusing) and continuous shooting (burst mode). Select central focus point only. Set camera to Tv mode and set your shutter speed. The shutter speed is the tricky part. It needs to fast enough to keep the subject sharp. But slow enough to get the background blurred. There is no fixed rule as it depends on your focal length and the speed you move your camera … which depends on the subject speed and distance. The car above was shot at f=100mm, I would guess it was about 70m away and doing 80 km/hr. On that day I tried shutter speeds between 1/60 and 1/160. 1/60 was too slow, the car was not sharp. 1/100 and faster got good results. Some experimentation is required for your subject speed / distance combination.
4) Technique
Locate a spot where you want to take the image. Turn your body about 45 degrees to the direction from where the car is approaching. Once the subject approaches, look through the viewfinder. Keep the central focus point over the subject and press shutter half way to activate continuous focusing. Follow the subject and keep it under the central focus point by moving your camera. Try to move your camera only horizontally and as smooth / continuously as possible.
Once the subject is close to your chosen spot (but not there yet!), press the shutter through and hold it down, while you still follow the subject with your central fucus point. Release the shutter after the car (or whatever) has passed your reference point. In burst mode you will take about 3-5 shots (within a second) every time a car passes. That way you have the best chance to get the image at your chosen spot.
Try this with a variety of shutter speeds! Also give it at least 10 tries per shutter speed. This technique requires some practise. The number of keepers will improve over time. Also you will develop a feel for suitable shutter speeds depending on your subject.
5) Check the LCD screen - Once
Have a quick look at your image on the LCD screen. You will not be able to tell if your main subject is really sharp, but you will see if the background is blurred. After you have done that, switch the LCD off (or forget about it). As you shoot in burst mode, you will take many, many shots. Do not check them/ delete them on the screen. Keep shooting. Do the checking / deleting at home on your PC. Will save you lot’s of time.
Ok, now it’s time to find that racecar ;-)))
