What is ISO?
ISO is one of three important settings on your camera that is used to take a well exposed photo. The other two are Aperture and Shutter Speed. In traditional (film) photography ISO (or ASA) was the indication of how sensitive a film was to light. It was measured in numbers (you’ve probably seen them on films – 100, 200, 400, 800 etc). The lower the number the lower the sensitivity of the film and the finer the grain in the shots you’re taking. In Digital Photography ISO measures the sensitivity of the image sensor.The same principles apply as in film photography – the lower the number the less sensitive your camera is to light and the finer the grain. Higher numbers mean your sensor becomes more sensitive to light which allows you to use your camera in darker situations. The cost of doing so is more grain (although cameras are improving all the time and today many are able to use high ISO settings and still get very usable images). An example of a situation you might want to choose a higher ISO would be photographing an indoor sporting event where the light is low and your subject is moving fast. By choosing a higher ISO you can use a faster shutter speed to freeze the movement.