Photography Basics 4 – ISO

ISO refers to the sensitivity of the camera’s sensor (or of the film if you’re using a film camera).

Increasing ISO increases noise in a picture which shows as unwanted imperfections  particularly in solid blocks of colour in darker areas like pavement in shadow.

Have a look at the pictures below (you’ll see the differences more clearly on a monitor, especially if you zoom in).

They are all of the same scene at the same exposure. I’ve increased the ISO and used a faster shutter speed in each to achieve this. I’ve kept the aperture the same so the depth of field remains unchanged.

You’ll notice that as the ISO increases so does the noise and the pictures progressively degrade.

As a general rule use as low an ISO as you can (tripods for landscapes are invaluable even in good light).

That said, if you’re shooting sports or wildlife for example, don’t be afraid to increase the ISO. It’s far better to have a sharp shot with noise than a blurry one without.

There are, of course, noise reduction software packages and whilst these can be very useful just bear in mind that there is a trade off between noise reduction and retention of detail. If you’d like to know more about this and other aspects of photography there are more details here