Last week I talked about ISO. But that’s only a third of what makes up exposure. This week I want to talk about another part of the triangle. Shutter speed, or exposure time, is how fast the shutter moves or how long the shutter of the camera is open, exposing either the piece of film or digital sensor to light and controls how much movement is in the image. This is measured in seconds for long exposures and fractions of seconds for faster exposures. Unless you plan to use a tripod or some other form of image stabilization, you are going to want to stick to a speed of 1/60th of a second, or faster. Anything slower than this, you are likely to introduce what’s called “camera shake” when hand-holding the camera. This is when the camera moves during the exposure and the whole image is blurred because of this.
When you’re choosing what shutter speed to use, take a look at the scene and see if there’s any movement. If there is, you need to decide how you want to capture it. Do you want to freeze the action, or allow it to blur? Sports and nature photographers almost always want to freeze the action. To do this they’ll often use a shutter speed in the thousandths of a second. Take this hummingbird for example. It was shot at 1/2000th of a second, which froze all of the motion of its fast-beating wings.
Motion isn’t always a bad thing. Many landscape photographers will carry a variety of neutral density filterers with them so they can slow down their shutter speed if they’re stuck shooting during the day. Notice the smoothness of the water as it goes over the falls in this shot of the Des Moines skyline. Even with a high ISO setting, the exposure took roughly half a second to create. This doesn't sound like a slow shutterspeed, especially when it only takes about a third of a second to bink your eyes, but remember hand-holding your camera at anything slower than 1/60th of a second can introduce blur you weren't looking for.