Shutter speed is the length of time the camera shutter remains open. It is measured in fractions of a second, from 1/8000 of a second to several seconds or more. A fast shutter speed freezes motion. A slow shutter speed blurs it. The choice depends on the subject. A running athlete needs 1/1000 or faster. A waterfall at 1/4 second becomes silky. A night sky at 30 seconds captures star trails. Shutter speed is one of the three variables in the exposure triangle, along with aperture and ISO.

Shutter speed affects more than motion. It affects exposure. A slow shutter speed lets in more light, which is useful in low light. But it also increases the risk of camera shake. The rule of thumb is to use a shutter speed at least as fast as the reciprocal of the focal length. A 50mm lens needs at least 1/50 second. A 200mm lens needs at least 1/200. Image stabilization allows slower speeds. A tripod eliminates the problem entirely. Shutter speed is also a creative tool. It controls how time is rendered in a photograph. A fast speed freezes a moment. A slow speed shows the passage of time.

Shutter speed guide

• 1/1000 and faster. Freezes fast action.
• 1/250 to 1/500. General action and handheld shooting.
• 1/60 to 1/125. Everyday scenes and portraits.
• 1/15 to 1/30. Blurs motion, requires steady hands.
• 1 second and slower. Long exposures, requires a tripod.

Shutter speed is not the same as exposure time. Exposure time is the total time light reaches the sensor. Shutter speed is the setting that controls it.