Shutter speed and motion
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In short
- Shutter speed is how long the sensor is exposed, usually a fraction of a second.
- Fast speeds (1/1000 s) freeze motion; slow speeds (1 s and longer) turn movement into blur.
- Doubling the time doubles the light: one stop.
- Handheld, stay at or above roughly 1 / focal length to avoid shake.
How long the light comes in
Shutter speed is written in seconds or fractions of a second: 1/4000, 1/250, 1/30, 1", 30". Each halving or doubling of the time is one stop of light.
Freezing and blurring
Fast shutter speeds stop motion. A running child needs about 1/500 s; a bird in flight or a ball in play may need 1/2000 s.
Slow speeds record movement as a trace. Around 1/2 s to a few seconds, flowing water turns silky and soft. Several seconds or minutes can turn car lights into lines and clear crowds from a square.
The waterfall in the photo above was shot with a long exposure: the rocks stay still and sharp, while the water becomes a smooth veil.
Camera shake
When you hold the camera in your hands, small movements smear the whole image at slow speeds. A classic rule of thumb is to use a shutter speed no slower than 1 divided by the focal length: about 1/50 s at 50 mm, 1/200 s at 200 mm. On cameras with a cropped sensor, multiply the focal length by the crop factor first.
Image stabilisation lets you go a few stops slower, but it only steadies the camera, not the subject. For anything slower, use a tripod or rest the camera on something solid.
Typical speeds
Sports and wildlife: 1/1000 s or faster.
Everyday people: 1/125 to 1/250 s.
Handheld in dim rooms: 1/30 to 1/60 s with stabilisation.
Water and night scenes on a tripod: 1/2 s to 30 s.