Advanced Techniques

ISO – Your camera’s sensitivity to light

Written by Digicamhelp Editor

Digital cameras are typically set by default to Auto ISO. ISO is a camera’s sensitivity to light. Learn when you may want to set it manually.

Atuo ISOISO is a camera’s sensitivity to light. The majority of digital cameras are typically set by default to Auto ISO. 

When set to Auto, the camera automatically sets the ISO according to light conditions: the brighter the light, the lower the ISO; the lower the light, the higher the ISO.

Use a flash or increase ISO?

Sometimes you can avoid using the flash by increasing the ISO. However one of the negative effects of using high ISO is that images will may contain noise to varying degrees: the higher the ISO number, the greater the visible noise. This is much more true for small sensor digital cameras than ones that have large sensors.

ISO camera settingsMany users prefer to manually adjust the camera’s ISO. It gives them more control over the amount of noise that appears in images.

ISO and noise

On many consumer digital cameras, selecting an ISO number of 100 or below produces little noise. Test each ISO number under a variety of lighting conditions until you become familiar with the noise your camera produces at each setting.

If images are noisy, noise reduction programs do an effective job at eliminating some of it, though fine detail may be sacrificed. So it’s preferable to try to produced noise-free or low noise images if you can.

Low ISO settings

High ISO settings

ISO 100-200

ISO 200 and above

More light needed Less light needed
Less noise Increased noise
More image detail Less image detail
Larger aperture +/or longer shutter speed Smaller aperture +/or faster shutter speed


Question markShould you use high ISO?

When deciding whether or not to set a high ISO number, keep in mind how the images will be used. Depending on the amount,, noise is often barely noticeable when images are reduced in size for printing, viewing on a computer or posted to a social media site. Importantly, an acceptable level of noise in a photo is preferable to not getting the shot at all.

An option to raising the ISO is to select a lower number and set your digital camera on a tripod or level surface. Use the self-timer or a remote control to trigger the shutter. This will eliminate camera shake.