Every photo is a balance between three settings. Learn what each does and you can fix almost any exposure problem in seconds.
The three settings
Aperture is the size of the lens opening, written as an f-number such as ƒ/1.8 or ƒ/8. A lower number means a wider opening: more light and more background blur.
Shutter speed is how long the sensor collects light, such as 1/250 s. Faster freezes motion. Slower blurs it.
ISO is the sensor’s amplification. Higher ISO brightens the image and adds noise.
What each one changes in the picture
| Setting | Exposure | Creative effect |
|---|---|---|
| Aperture | Light through the lens | Depth of field |
| Shutter speed | Time the sensor is exposed | Motion blur |
| ISO | Brightness amplification | Noise |
Stops: the shared language
A stop is a doubling or halving of light. Going from ƒ/2.8 to ƒ/4 is one stop darker. Going from 1/125 to 1/250 is one stop darker. Going from ISO 400 to ISO 200 is one stop darker. To keep the same exposure, trade one for another: close the aperture a stop and slow the shutter a stop.
Starting points
- Portraits: ƒ/1.8 to ƒ/2.8, 1/200 or faster, ISO as low as the light allows.
- Landscapes: ƒ/8 to ƒ/11, base ISO, tripod if the shutter gets slow.
- Action: 1/1000 or faster, widest practical aperture, raise ISO to compensate.
- Low light handheld: widest aperture, shutter around 1/focal length, then raise ISO.
- Video: shutter at about double the frame rate (1/50 for 24p), then control exposure with ND filters, aperture and ISO.
Use a mode that helps
Aperture priority (A or Av) lets you set the look and lets the camera pick shutter speed. It is the best learning mode. Add exposure compensation to brighten or darken the result.
Next steps
Once exposure feels natural, the biggest upgrades come from light and lenses. See our lens mount guide and crop factor guide.
Frequently asked questions
What is a stop of light?
A stop is a doubling or halving of light. Opening the aperture one stop, halving the shutter time or doubling ISO each changes exposure by one stop.
What shutter speed should I use for handheld photos?
A common starting point is 1 divided by your focal length, for example 1/60 for a 50mm lens. Stabilization and steady hands can let you go slower.
What shutter speed is best for video?
The 180-degree rule suggests a shutter speed of about double the frame rate: 1/50 for 24p, 1/60 for 30p, 1/120 for 60p.