Shutter speed
How long the sensor is exposed decides whether movement is frozen or smeared. It is the most visible of the three controls.
The shutter is a curtain in front of the sensor. Shutter speed is how long it stays open, and it is the control whose effect is easiest to see.
The numbers
Written as fractions of a second: 1/1000, 1/500, 1/250, and so on down to whole seconds. Each step in that sequence halves or doubles the time, and so halves or doubles the light — one stop.
The printed numbers are rounded. A camera marked 1/125 is really giving you 1/128; the sequence is powers of two underneath, which is what makes the stops exact.
Freezing and smearing
Anything that moves while the shutter is open records in more than one place, and that reads as a smear along the direction of travel.
| Subject | Roughly enough to freeze |
|---|---|
| A person standing, small movements | 1/60 |
| Someone walking | 1/250 |
| Someone running | 1/500 |
| A cyclist or a car at speed | 1/1000 or faster |
Three things push those numbers up: a faster subject, a closer subject, and a longer lens. All three amount to the same thing — how quickly the subject crosses the frame.
Blur on purpose
A smear is not a fault unless you did not want it. Slow shutter speeds are how flowing water becomes silk, how traffic becomes ribbons of light, and how a photograph says that something was moving.
The condition is that everything else stays sharp. That means the camera cannot move — so a tripod, or a wall, or anything solid. Otherwise you get camera shake on top of the intended motion blur, and the result just looks like a mistake.
The cost
Every stop of shutter speed you gain has to come from somewhere. Doubling the speed halves the light, so it must be paid for with a wider aperture or a higher iso.
This is the trade you will make most often. Freezing a subject in poor light is exactly the situation where all three controls fight each other.
Try it
Freeze it first, then do the opposite:
Freeze the pendulum
The bob is swinging past a ruled backdrop. Catch it sharply as it passes through the centre, where it is moving fastest — without over- or under-exposing the shot.
Loads an interactive 3D camera simulator.
Key takeaways
- Each step of the shutter sequence halves or doubles the light — one stop.
- How fast you need depends on subject speed, distance and focal length.
- Movement across the frame smears far more than movement towards the camera.
- Deliberate blur needs the camera held still, or it just reads as a mistake.
Common questions
What shutter speed freezes a person walking?
Around 1/250 for someone walking across your view at a normal distance. Running needs 1/500 or faster. Closer subjects and longer lenses need more, because they cross the frame faster.
Why do slow shutter speeds need a tripod?
Because below roughly one over the focal length, your own movement blurs the whole frame. A tripod removes that, which is what makes deliberately blurred water or traffic possible.
Next steps
The exposure triangle
Three controls decide how bright a photograph is, and each one changes something else as well. That trade-off is the whole of exposure.
Holding the camera steady
Most photographs that beginners call out of focus are not. They are blurred by the photographer's own movement, and that has a specific cure.
Aperture and depth of field
The aperture controls light and how much of the scene is sharp at the same time. It is the control that most changes how a photograph feels.