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In film photography, a measure of a film’s “speed” or light sensitivity. The higher the ISO, the more sensitive the film. The sensitivity of digital camera sensors are also rated using the ISO scale. ISO stands for the International Organization for Standardization (or, International Standards Organization, if you want an acronym that fits better) the people who define, among many other things, the spec used to gauge light sensitivity. ISO is equivalent to the old ASA scale (American Standards Association) which has since been discontinued. (Curiously, ISO is not meant to be an acronym for anything, it’s allegedly a pun on the Greek prefix “iso-” meaning “same.”)

ISO is one of three exposure controls that you have on a digital camera, in addition to aperture and shutter speed selection. Each exposure control allows you to affect different image characteristics.

You can learn about each of these controls, how to use them, and how they affect your final image in Chapter 7 of Complete Digital Photography, 3rd edition.

One Response to “ISO”

  1. boso de Niro

    Thanks for declaring front and center that ISO in cameras is not a conventional acronym! Do you know how many newbies waste millions of man hours hunting for this useless factoid! You were the only one out of millions of links on Google.that had the good sense to say in the abbreviated link on Google — What is wrong these people! Thanks again..