Understanding The ISO in Photography for Beginners

In previous article we’ve seen that we can control the exposure through choices for Shutter Speed, Aperture and ISO. Although understanding the ISO seems to be very simple, it has its own challenges. In this article I will discuss some popular questions that I have received about the ISO.

What is ISO

ISO in photography terms is a measurement unit which measures the sensitivity of our media (film or digital sensor) to light. In the simplest terms the higher the number the more sensitive the media is to light.

Low Light, Higher ISO

When it comes to low light situations, to maintain a certain shutter speed or to use a desired f-stop, we have to adjust the ISO. The higher (Faster) ISO setting allows us to shoot with a faster shutter speed or higher f-stop. But it can introduce lots of grain (Digital Noise) in our images. The high ISO reduces the sharpness and dynamic range of the camera’s sensor, which I will cover in other articles.

What is the best ISO?

As a rule of thumb, photographers prefer to use the lowest possible ISO to keep the sharpness and dynamic range in their photos, but there are times when you want to capture a moving subject (such as sport photography or taking photos of kids) and there is no other choice than to use a higher ISO setting. After all a noisy (grainy) photo is far better than a blurry one!

What is Digital Noise (Grainy photo)?

In this article I am going to show you some samples of different ISO and discuss some guidelines for choosing your ISO setting.

Here are photos for comparison. I shot the first one at 100 ISO and the second one at 12800 ISO.

As you can see the lower ISO image is sharper, has better colour and more details in highlight and shadow (more dynamic range).

Here is a comparison at 100% view.

What is the best ISO setting?

Generally speaking you want to stay with lowest ISO setting when you shoot landscape, portrait and detailed images such as macro photography. For moving subjects you should consider the lowest possible ISO. As an example if your subject is a bird in flight and you want to keep everything sharp and you are using a 300mm lens at f5.6, your minimum shutter speed should be 1/1000s or faster. With your shutter speed set to 1/1000s and your aperture at f5.6, check your camera’s light meter for exposure. If your camera cautions for under-exposure (usually there is some kind of warning that tells you the exposure is not correct), instead of reducing shutter speed (which results in a blurry photo) or opening up the f stop (which will give a shallow depth of field), increase the ISO till your camera’s built in meter stops asking for more light!

There is much to learn about ISO and dynamic range which I will cover in future articles. For now, happy ISO shooting!

Stay tuned for my next article about Auto ISO and as always feel free to contact us if you have more questions. Follow us on Facebook, Instagram and Twitter for new tutorials and tips.

Ted and the Omnilargess Team