One way that the shutter speed impacts an image is by determining how bright or dark the image is.  Read the previous post for more details.

But, as with the other camera settings, there is a trade-off involved. There are certain situations where you will always want a quick shutter speed, and there are other situations where you will want to use a slow shutter speed.

Freezing Action vs. Motion Blur

The problem with leaving the shutter open is that if your subject moves, your image is going to end up blurry. If you’re taking a picture of a moving subject, you need to have a quick shutter speed to freeze the action and prevent motion blur.

In this image, for example, a relatively quick shutter speed helped freeze the runners in place. Yes, they are moving pretty fast, and with a slow shutter speed he would have come out quite blurry. This is the final leg of a 4 x 100m relay. While these high school athletes are no Usain Bolt’s, they’re running as hard as they can.

But the quick shutter speed, 1/1000th of a second, freezes them in place. The shutter isn’t open long enough to register the subjects’ motion, so they appear to be standing still in the picture.

Compare that to this picture, where there is very clearly a motion blur problem.

In this case, my student photographer accidentally used a slow shutter speed (1/30th of a second). Since the football players are moving pretty quickly, they move in the space of time that the shutter is open. This blurs the players across the frame, leading to a lackluster, blurry image.

So What’s a Good Shutter Speed?

Well, that’s a good question. And the answer will vary.

Another thing to look out for is “camera shake.” Instead of the subject moving, the camera itself moves… causing a slightly blurry image. The problem is magnified by longer focal lengths (i.e. zoom lenses). So, as a rule of thumb, you should try to use a shutter speed that’s equal to the focal length you’re shooting at.

If you’re using a 50mm lens, shoot at 1/50th of a second or quicker. If you’re using a 400mm lens, shoot at 1/400th of a second or quicker. A steady hand, a mono-pod, or an image stabilization system can reduce this problem… but the idea is to use a quicker shutter speed with a longer focal length.

Other than that, it’s all relative. If you’re shooting a quickly moving subject (i.e. sports), you’ll want a minimum of 1/125th of a second. Depending on how quickly and in what way the subject is moving… this might be ok. But, you’ll probably get better results if you can get up to 1/250th of a second or faster.

The problem? You still need to let in enough light for the image to come out. If you’re shooting sports outdoors, this usually isn’t a problem. But, if you’re shooting sports indoors, you might have to compromise and settle for a little motion blur in exchange for bringing in enough light.

Is Blur Always a Bad Thing?

Not necessarily. There are certain artistic reasons for including motion blur into a picture. Read the next post on when motion blur isn’t a bad thing to see a couple examples.