For portraits, use your camera’s lowest native ISO (often 100 or 200) when there is plenty of light, and raise it only as much as you need to keep the shutter speed fast enough and the aperture where you want it. There is no single best value. ISO is usually the last setting you adjust, after aperture and shutter speed.
How ISO fits with aperture and shutter speed
Exposure depends on three things. Aperture controls depth of field and how blurred the background looks. Shutter speed controls motion blur. ISO controls how much the camera amplifies the signal, and higher values add visible noise. A sensible order is:
- Choose the aperture for the look you want, such as f/2 for a soft background.
- Choose a shutter speed that avoids blur. See shutter speed for portrait photography.
- Set ISO to get the exposure you want.
ISO by lighting
| Lighting | Starting ISO |
|---|---|
| Bright sun, or large window light | 100 to 200 |
| Overcast or open shade | 200 to 400 |
| Bright indoor room | 400 to 800 |
| Dim indoor or evening, no flash | 800 to 3200 or more |
| Flash or studio strobes | Base ISO usually |
Values are rough starting points. Modern cameras vary widely in how clean their higher ISO files look.
Is ISO 800 too high?
Usually not. On most recent cameras, ISO 800 looks clean at normal viewing sizes, and noise often matters less than a sharp, correctly exposed photo. Older or smaller-sensor cameras may show more noise, so test yours by shooting the same scene at several ISO values and viewing them at full size. A noisy but sharp portrait is often more useful than a clean but blurred one.
Auto ISO
Auto ISO is helpful when portrait light changes, such as at events or when subjects move between rooms. Set an upper limit, such as ISO 3200 or whatever you find acceptable, and a minimum shutter speed if your camera allows it. Use exposure compensation if skin tones look too dark or bright, since the meter can be fooled by bright backgrounds.
Flash and studio
With flash, ISO mainly affects how bright the ambient light looks relative to the flash, so you can often keep ISO at base to keep files clean and use flash power for exposure. Raising ISO makes the background brighter and also makes the flash exposure brighter at a given power, so you may need to turn the flash down. Check your flash manual for the specifics.
Reducing noise
- Expose well. Underexposing and brightening later often increases visible noise, especially in shadows on skin.
- Use a wider aperture or slower shutter speed if the subject and lens allow it.
- Shoot RAW so you can apply noise reduction with controlled settings.
- Add light, such as a window, reflector or flash, instead of raising ISO.
Street portraits taken in changing light follow similar logic, as covered in our street photography camera settings guide.
FAQ
What f-stop should I use for portraits? Many photographers start between f/1.8 and f/4 for a softer background, and use f/5.6 or higher for groups so everyone is sharp. Our guide to the best lens for portrait photography covers which fast lenses make the wide end practical.
What ISO is best for indoor portraits? Often 400 to 1600 without flash, depending on window light and lens speed.
Should I always use the lowest ISO? Not necessarily. If a low ISO forces a slow shutter speed, the resulting blur is usually worse than the noise from a higher ISO.