With film cameras, exposure is controlled by aperture and shutter speed settings at a fixed ISO setting (which is dictated by your film). Digital cameras allow you to change the ISO setting with just the push of a button, but on most models this can be performed automatically with your ‘Auto ISO’ function.
This is very useful when the lighting conditions are changing quickly – when you’re moving from outdoors to indoors, or from bright sunlight into shadows.
With the Auto ISO function set to On, your camera will select the lowest ISO for the lighting conditions to maintain maximum image quality.
If light levels fall, the camera will increase the ISO up to a maximum setting you’ve chosen, maintaining a good exposure at your chosen aperture and shutter speed settings. On some camera models, you can also set the minimum shutter speed at which Auto ISO kicks in.
For example, if this is set to 1/60 sec, the camera will continue to shoot at the lowest possible ISO until the shutter speed required to make an accurate exposure drops below 1/60 sec, at which point Auto ISO increases the ISO to maintain this shutter speed. This is a handy way to avoid blur caused by camera shake, and it enables you to concentrate on the subject.
The downside? Auto ISO may lead to over-exposure in very bright conditions, depending on your aperture setting. It doesn’t work when using flash, either.
Follow our quick, three-step tutorial below to find out how to set your Auto ISO function.
How to set your Auto ISO
Find the Menu
Press the Menu button, then go to Shooting Menu and scroll down to ISO Sensitivity Settings. Press OK. This brings up the ISO Sensitivity Settings menu screen. Set the ISO Sensitivity to the lowest setting available – typically ISO 100 or 200.
Switch to Auto
Use the multi-controller to scroll and highlight ISO Sensitivity Auto Control. Select On then OK. ISO-AUTO will be displayed on the rear control panel and in the viewfinder. At the default setting (Off) ISO sensitivity will remain at the value selected manually.
Take some control
To set an upper limit for ISO, highlight Maximum Sensitivity and select a value. At high ISO values image noise will be apparent. Set the Minimum Shutter Speed value to determine the setting at which Auto ISO is activated. Press OK to confirm.