ISO

Sensitivity of film or a digital camera sensor.

The higher the ISO number the more sensitive the sensor/film and the less light needed to form an image, ie higher ISO means you can take images in lower light levels without needing slow shutter speeds. But high ISO can lead to noisy, grainy images, particularly on early digital cameras.

The ISO of a digital camera sensor is actually a fixed property of the sensor, and the variation in sensitivity is created by amplifying the signal to a greater or lesser degree.

The term ISO came to be used for sensitivity because the International Standards Organisation - ISO - produced a standard for film speed which was universally adopted. When digital cameras came along the same standard was continued.

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