What Is ISO Speed?

People often ignore ISO because they don't fully understand what it does, but once you do, you'll be making use of this clever tool all the time - and not only in low light conditions.

ISO is a kid of bonus exposure control which can help you out of all sorts of tricky situations.

In this video we'll explain

• ISO introduction
• How ISO works
• ISO range and shooting in low light
• Grain and noise
• When to use ISO rather than flash

Instead of using flash for this indoor portrait I increased the ISO speed to make the camera more sensitive to light. Why would I not use flash?

Small on camera flashes have a nasty harsh look to the lighting which looks so stark and unflattering. Watch the video and you'll see what I mean. As far as I'm concerned ISO speed is king.

Don't miss our Using ISO speed films...