ISO on a phone camera: what it does and what to set
ISO is the setting that brightens your photo in low light, at the cost of noise. Here's what it actually does on a phone, how it trades off against shutter speed, and what to set for common scenes.
What ISO does on a phone
ISO controls how much the camera amplifies the signal from the sensor. A higher ISO makes the picture brighter without letting in more light. Each doubling, from ISO 100 to 200 to 400, makes the image one stop brighter.
Most phones go from around ISO 50 or 100 up to several thousand. The lowest value is the sensor's base ISO, where image quality is best.
Why high ISO looks noisy
Amplifying the signal amplifies its noise too. A phone sensor is tiny and collects little light, so noise appears early: speckled grain, blotchy colour in shadows, and lost fine detail. The phone's noise reduction then smooths it, which can make textures look painted.
ISO and shutter speed work together
On a big camera, brightness comes from three settings: aperture, shutter speed and ISO. Most phones have a fixed aperture, so on a phone it's really two: shutter speed (how long light is collected) and ISO (how much it's amplified).
- Halve the shutter time and you need to double the ISO to keep the same brightness.
- A slower shutter lets you keep ISO low, but risks blur from shake or movement.
- So the rule is: use the slowest shutter speed you can hold steady, then the lowest ISO that gives the brightness you want.
What ISO to use
| Scene | ISO to start with | Shutter speed |
|---|---|---|
| Bright daylight | Lowest (50–100) | 1/500 s or faster |
| Overcast or shade | 100–200 | 1/125–1/250 s |
| Indoors by a window | 200–400 | 1/60–1/125 s |
| Dim room, evening street | 800–1600 | 1/30–1/60 s |
| Night, phone on a tripod | Lowest | As long as needed |
| Moving subject in low light | As high as needed | 1/250 s or faster |
These are starting points. Check the result, and watch the histogram. For a full set of scenes, see the pro mode cheat sheet.
Auto ISO or manual?
Auto ISO is fine most of the time. Set ISO by hand when you want control over the trade-off: low ISO and a tripod for a clean night shot, or a high ISO to freeze a moving subject in dim light. Also set it by hand for video, so brightness and noise don't change in the middle of a take.
Setting ISO in One Camera
One Camera Pro puts ISO, shutter speed, focus and white balance on real dials, for photos and in Pro Video, with a per-channel histogram and zebras to check exposure. The available ISO range comes from your phone's camera. Pro is a one-time purchase, and one short ad unlocks it for 24 hours. New to manual mode? Start with manual camera settings explained.
Questions
What does ISO mean on a phone camera?
ISO sets how much the camera amplifies the sensor's signal. Higher ISO makes the picture brighter in low light, but adds noise and loses fine detail.
What is the best ISO for a phone camera?
The lowest ISO that gives a sharp, bright enough photo: about 50 to 100 in daylight, 200 to 400 indoors, and 800 to 1600 in dim light. On a tripod at night, keep it low and use a longer shutter speed instead.
Why are my phone photos grainy?
Usually because the camera raised the ISO in low light. Add light, steady the phone so a slower shutter speed works, or use Night mode, which merges several frames to reduce noise.