SHUTTER SPEEDS
Discover how your shutter speed affects your exposures, and how faster or slower speeds capture movement
The shutter speed is one of three fundamentals of your exposure for regulating the brightness of your pictures. The shutter speed setting works in tandem with the aperture (and ISO) to help you take a perfect exposure, in a variety of lighting conditions.
Shutter speeds are easier to understand than apertures as the scale is more logical. Shutter speed – or length of time the shutter is open – is simply measured in fractions of a second. So 1/500 sec shutter speed lets through half as much light as 1/250 sec.
The shutter speed range is also more extensive than the aperture range, as you control it with your EOS camera. The top speed on EOS cameras is usually around 1/4000 sec, while the longest automatically set shutter speed is 30 secs.
Allowing for movement
You can set your shutter speed to control the amount of motion blur (or lack of it) in a picture. This effect is only noticeable if either the camera or the subject is moving. Even with stationary subjects, shutter speed is crucial if the camera is handheld – the slightest movement of your body results in camera shake and a blurred image. If the shutter speed is fast enough, this movement becomes imperceptible. Just how fast the shutter needs to be to avoid camera shake depends on a number of factors (including whether you use an image-stabilized lens, and how windy it is), but the most important factor is the focal length of the lens. The longer the focal length, the faster the shutter speed you need. A good rule is your minimum shutter speed should be ‘one over’ the focal length. So, with a 50mm lens setting, use 1/50 sec or faster, and 1/200 sec or faster with a 200mm lens.
Use a solid tripod, though, and the camera shake problem is eliminated, giving you complete control of shutter speed – and therefore also a greater choice of apertures.
Moving subjects also affect shutter speed choice. If you want the subject to appear sharp in the shot, a fast enough speed (such as 1/1000 sec) must be used. However, it is not essential for everything to be completely still – many moving subjects are more artistically captured with a slower shutter speed, such as the rushing water in the above shots at around 1/2 sec. The secret is to use a speed that is long enough to make the blur look deliberate. Using a tripod is essential, so static parts of the scene are sharp, and only moving parts are blurred.