by Sheree Zielke

Created on: November 06, 2008   Last Updated: October 19, 2010

"What does ISO stand for?" my bright-eyed student asks. I am always asked this question in my digital camera classes. My answer? "What the letters stand for have very little importance. What is more important is that ISO is part of the magic triangle on all cameras that works towards ensuring a perfect exposure."

International Organization for Standardization - see, the words mean very little to the actual function that ISO performs on your digital camera. ISO controls your camera's sensor's sensitivity to present light. It is a function that is invaluable to all photographers, and must be learned if you want to truly tame your exposures.

Cameras (in an AUTO mode) and photographers have perfect exposure as their ultimate goal. To achieve a perfect exposure or exposure value (EV), three things must be set in concert with one another: the shutter speed, the aperture width (f/stop), and the ISO .

To put it very simply, your digital camera's ISO control helps your camera to "see" in the dark. This control enables your digital camera to record an image in low light situations. Even the simplest understanding will help you improve your digital photographs, but be sure not to confuse your camera's ISO settings with your camera's shutter speed; they work together, but they are not similar. One controls sensitivity to light, while the other controls the amount of light striking your camera's image sensor.

In our modern digital cameras, ISO settings have replaced ASA (film speed) once acquainted with our old film cameras. ISO numbers can range from a very low 80 and can go as high as 6400 on many compact point-and-shoot cameras. The more expensive DSLR cameras (single lens reflex cameras with interchangeable lenses) can sport ISO settings as sensitive as 12,800 and higher. The lower numbers 80, 100, 200 are reserved for brighter light, and sunny days. Mid-range numbers like 400 and 800 are necessary once the light diminishes, like the low light found in deep shade, at dusk and dawn, and inside a building. The higher settings of 1600 and greater are necessary when light is extremely low, like in concert halls, museum, etc.

Since a great deal of our picture-taking is done in low light (nighttime parties, museums, concert halls, sporting events), understanding when to adjust your camera's ISO setting will also help you to capture a stable image devoid of camera shake (blur). The more sensitive you can make your camera to existing light, the faster your camera will be able

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