What is ISO?
Digital Photography Basics

What is ISO and why should you care? If you want to improve your photography understanding basic digital photography terms like ISO is vital. Here's a description of ISO that will help you understand this term.

In film photography, ISO refers to film speed. Film comes in speeds like 100, 200, 400, and 1600. Each film speed is used in different lighting situations. The lowest numbers are used in brighter light situations and the higher numbers in dim lighting.

In digital photography, ISO is used to refer to the sensitivity of the camera sensor to light. You can set the ISO in your camera menu. Each camera is different so you'll have to read your manual to find out how to set it. When not set manually your camera will determine which ISO to use on its own. The settings will appear in numbers like film speed numbers.

ISO settings affect the shutter speed and aperture you'll need to take a high quality picture. If your camera sensor is very sensitive to light because it's set at a high ISO you'll require less light to enter the camera to get a properly exposed picture. This means that you'll be able to have the shutter open for less time. That is important because the longer your shutter is open the more motion blur you'll get in your picture. You'll also be able to have a narrower aperture which will increase the depth of field in your picture.

There is a problem with using high ISO settings. The higher the ISO you use the more noise will appear in your pictures. Noise is a grainy distortion that can occur in pictures. The lower the ISO setting the clearer your picture is. Ideally, you should set your ISO to as low as you can in each lighting situation.

Use low ISO settings like 100 in bright lighting situations. When you must take pictures in dimly lit situations use higher ISO settings. I take a lot of stage photos and always have to use ISO 1600 or greater in those situations.

One thing I really like about digital photography is that you can change your ISO settings between pictures. When using film you have to use up the entire roll of film before you can change your ISO by changing film.

Now that you can answer the question "What is ISO?" check out other articles on this site to learn more.

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