Tuesday, August 11, 2009

What is ISO?

The ISO setting on your camera controls the sensitivity of your digital sensor. Increasing the ISO (changing it to a higher number) makes your sensor more sensitive to light and lowering the ISO makes the sensor less sensitive. This has an important effect on exposure because changing your ISO changes the amount of light your sensor needs to produce a correctly exposed image.

In the real world, here's what this means: when you set your ISO higher you can take pictures in darker settings (all else being equal.) However, increasing your ISO also has a negative effect on the quality and clarity of your images. (Later we will discuss this relationship between ISO and digital noise.)