Using Auto ISO
Learn to make the most of your ISO setting
You don’t have to be a new photographer to appreciate the benefits of allowing your EOS camera to choose an ISO speed for you. When you’re in the thick of the photography action, it’s one less setting that you will need to think about.
It’s fair to say that Auto ISO used to be a bit of a blunt tool. On the EOS 40D, for instance, Auto ISO defaulted to ISO400 in almost every situation, even in bright sunshine. Today’s Auto ISO is a world away from that rough usage. Now, you may be able to set not just the ISO range that Auto ISO can select a sensitivity from, but the minimum shutter speed that the Auto ISO should try to maintain as the light changes.
Of course, you are still sacrificing an element of
control with Auto ISO enabled. This means you can’t switch off when you’re shooting, as the camera might choose an ISO speed that it determines will give a ‘correct’ exposure based on the its meter reading. Faced with bright or dark subjects, it can give a wrong exposure, so you may need to override Auto ISO by using exposure compensation.
Auto ISO comes into its own when light levels are fluctuating, as it will adapt the sensitivity to maintain a consistent, usable exposure when you move from a bright area to a dark one, or vice versa. As a result it can be a good choice for street photography, travel photography and other types of ‘walkabout’ photography – particularly on a sunny day when there will be pockets of sun and shade.