What is ISO?

High ISO

High ISO = Grainy

ISO measures the sensitivity of the image sensor. It is measured in numbers - 100, 200, 400, 800, etc. The lower the number the less sensitive your camera is to light and the finer the grain Higher ISO settings are generally used in darker situations to get faster shutter speeds, for example inside a church. However, the result of having a higher ISO means noisier shots. 100 ISO is general accepted as 'normal' and will give you crisp shots with little noise or grain.

ISO impacts the aperture and shutter speed needed for a well exposed shot. For example, if you bump your ISO up from 100 to 400 you'll notice that you can shoot at higher shutter speeds and/or smaller apertures.

When choosing the ISO setting ask yourself the following questions:

  1. Light - Is the subject well lit?
  2. Grain - Do I want a grainy shot or one without noise?
  3. Tripod - Am I using a tripod?
  4. Moving Subject - Is my subject moving or stationary?

Situations where you might need to use a higher ISO setting include:

  • Indoor Sports Events
  • Concerts
  • Churches
  • Wedding Receptions
  • Birthday Parties

Of course the disadvantages of using a higher ISO setting is noisier shots.

Read more at Digital Photography School