The exposure triangle

The big idea

Three dials, one photo

Shutter speed, aperture and ISO each do two jobs: they change how bright the photo is, and each adds its own creative effect. Change one and the brightness shifts — so you balance it with another. That balancing act is the exposure triangle.

Control 1

Shutter speed

How long the sensor stays open to light. Slow = more light, and moving things blur. Fast = less light, and motion is frozen sharp.

Control 2

Aperture

How wide the lens opens. Wide (a low f-number like f/1.8) = more light and a shallow depth of field — a blurry background. Narrow (a high f-number like f/16) = less light and more of the scene in focus.

Control 3

ISO

How sensitive the sensor is to light. High ISO brightens a dark scene — but adds noise (grain). Low ISO gives the cleanest image, but needs plenty of light.

The balance

Give and take

Every change costs light somewhere. Speed up the shutter to freeze action → the photo darkens → open the aperture or raise the ISO to win the light back. There’s no single “right” setting — there’s the right trade-off for the shot you want.

Worked example

Freeze + blurred background

You want a skater frozen mid-jump with a soft, blurry background. That means a fast shutter (to freeze) and a wide aperture (for shallow focus) — both hungry for light. If it’s still too dark, your last lever is ISO: push it up and accept a little grain. Try it below ↓

Three dials, one photo

Shutter speed

Aperture

ISO

Give and take

Freeze + blurred background

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