Definition
Shutter speed is how long the camera's shutter stays open for each exposure, written in seconds or fractions such as 1/1000s, 1/60s or 2s. It controls two things at once: how much light reaches the sensor and how movement is recorded. Fast speeds freeze action; slow speeds blur it, along with any camera shake.
A cyclist frozen at 1/1000s, f/4, ISO 400 starts to blur at 1/250s. That slower speed lets in two more stops of light, so close the aperture to f/8 to keep the same exposure. Handheld with a 50mm lens, stay at about 1/60s or faster (one over the focal length) to avoid camera shake.
Calculate it for your own shot with the Exposure Calculator.
Also used in: ND Filter Calculator, Lens & Settings Recommender, EXIF Viewer
Shutter speed is where a photographer decides how time itself looks in the frame. Freeze a hummingbird's wings at 1/4000s and the image shows something the eye can never quite catch; let a river blur at 1/4s and you get a sense of flow that no single instant holds. It also sets a hard limit on hand-holding.
Below roughly one over the focal length, so about 1/60s on a 50mm lens, camera shake starts to smear fine detail even when the subject is still, and stabilisation only buys two or three stops back. This is a common indoor mistake: someone shoots a birthday party at 1/30s to keep the ISO down, and half the frames have soft faces from a mix of subject movement and hand shake. The usual fix is to accept a higher ISO so the shutter can get back to 1/200s.
At an outdoor track meet, a runner crossing the frame is rendered three ways from one spot. At 1/1000s, f/4, ISO 400, every limb is frozen and the background is still. Drop to 1/250s and the runner is mostly sharp, but hands and feet smear just enough to read as speed. Pan the camera with the runner at 1/30s and the body stays recognisable while the background stretches into horizontal streaks.
Each drop also doubles the light, so going from 1/1000s to 1/250s is two stops that have to leave through a narrower aperture or lower ISO. Flash is a separate trap: try 1/500s with a hotshoe flash on a body that syncs at 1/200s, and a black band from the shutter curtain covers part of the frame. Panning at 1/30s with a 300mm lens adds its own problem, since camera shake at that focal length smears the background more than the pan intends, so a monopod earns its place even for the deliberately blurred frame.
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