What Does the ISO Setting on My Camera Mean and How Do I Use It to Take Better Pictures?

This article discusses what the ISO setting on your camera does and explains the impact of changing the ISO on the look of your final photograph.

In simple terms, the ISO rating determines how sensitive the digital sensor on your camera is to light. It is a throwback to the film days when film speed was rated by the ISO standard (the smaller the number, the lower the light sensitivity of the film).

The same principle applies nowadays to the digital sensor on a camera. The lower the ISO the less sensitive the digital sensor is to light hitting it and, therefore, the more light required (through the shutter speed or aperture variables) to achieve a correctly-exposed photograph.

It is important to bear in mind that while a higher ISO will allow for photographs to be taken in low-light or indoors and still achieve a suitable exposure, the enemy of digital (and film) photographers which arises from a higher ISO setting is “noise”. Noise arises as a by-product of using a more sensitive sensor and can result in pictures having a grainier look. This is particularly relevant if a photograph is enlarged.

In the right circumstances, however, noise can be used for creative effect (for example, if you are trying to create an older black-and-white look to your picture, some level of noise can often add character to the picture). This is a fine balance, however, and too much noise can ruin pictures.

It is also important to note with a digital camera that a lower ISO typically uses more memory to save the photograph (this may be relevant if you are running short on memory card space).

Typically, unless I am deliberately trying to use noise to create a particular effect (e.g. add a “grain” effect to a picture) or I am photographing indoors and unable/unwilling to use flash lighting, I aim to use the smallest ISO setting possible to ensure maximum quality from my pictures. This allows for photographs to be enlarged in future, without fear of noise disrupting the quality.

An ISO setting can be set on most digital cameras – check your manual for advice on how to use your particular camera’s settings.

You should experiment with different settings to get an understanding of which ISO gives the best outcomes in different circumstances. Having a working understanding of the ISO setting will allow you to choose the appropriate setting for the circumstances infront of you. Have fun!