Digital cameras are typically set by default to Auto ISO. ISO is a camera’s sensitivity to light.

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.

Sometimes you can avoid using the flash by increasing the ISO, but one of the negative effects of using high ISO numbers is that images will most likely contain noise to varying degrees: the higher the ISO number, the greater the visible noise. This is much more true for compact digital cameras than digital single lens reflex cameras.

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Many 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 best to try to produced noise-free or low noise images to the extent you can.

To use, or not to use high ISO…that is the question

When deciding whether or not to use an high ISO number, keep in mind that the visual presence of noise is often barely noticeable when images are reduced in size for printing and/or viewing on a computer. In addition, 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. Use the self-timer or a remote control to trigger the shutter to eliminate camera shake.