Pixiq

Once upon a time, in days of old, when we shot on film and had to fend off dragons simultaneously, we also had to choose the ISO of our film when we bought it. 100? 200? 400? Huh? Now it’s just a button on our cameras and we can change it every shot. But what is ISO? What does it do? How does it work? Why’s it important? Well, Matt Druin is here to explain it all.

Maybe you’ve heard the term ISO thrown around, maybe not. Either way, ISO can be an important tool if you understand it, and use it correctly. So what is ISO? Well, photographically speaking, an ISO number refers to a film’s sensitivity to light, when using film cameras.

But…ehm…Matt, we’re mostly using digital cameras today…

Okay, yes, today, many people are using digital cameras, but the meaning has not changed. Instead of film, digital cameras use a sensor to capture the image, and ISO refers to the sensitivity of the sensor.

Ah, gotcha. So how do we measure this sensitivity, then?

ISO is expressed as a range of numbers, such as, ISO 100-1600, or even higher on some of today’s digital cameras. The higher the number, the greater the sensitivity to light.

This was shot using ISO 100 in an aquarium, where it's pretty dark and using a flash isn't a great idea

Low vs High

There are many reasons you might choose a particular ISO setting. For example, a low ISO is generally preferred in sunny or brightly lit situations. You don’t need that much sensitivity light when there’s so much light around. On the other hand, a higher ISO setting may be needed in low light situations, like shooting at a museum, where flash and tripods, are commonly not permitted.

That sounds awesome!

But…

There’s always a but.

… using a higher ISO can cost you. It won’t necessarily cost you money, but instead, potential loss in quality of your photos.

This was shot using a much higher ISO. See how grainy it looks?

You’ve lost me now.

Let me explain. As the ISO setting increases, more amplification is used to capture light, this amplification in turn can cause grainy specs, or noise as it is called in photography, to appear in your shots. This noise is typically undesirable, because the image is not sharp, and does not look its best. At the same time, there are some instances where a photographer may want to introduce noise in a photo, to add to the feeling, or to help better tell the story of the shot.

Right, so there’s a trade-off: more sensitivity to light means lower picture quality. So what do I do?

Which ISO to use

Many photo editing programs offer quick fixes to unwanted noise issues, but really it’s best to use the correct ISO for your situation. Often, the lowest ISO available to you will be the best choice. This will allow you to capture the crispest image while limiting the introduction of noise.

But what if the light isn’t good?

Shot at ISO 800. Much better!

Of course, in low light situations, it may be necessary to use a higher ISO setting in order to capture the image. In which case it is recommended to avoid going to a higher setting then needed, if the cleanest image is your goal. If you can, use a flash and/or a tripod to help you get the shot you want without having to use a higher ISO setting, or at least limiting how high of a setting you must use. But in some circumstances, like in museums or at concerts, that’s not practical.

So what should I do about it?

More then likely, you will benefit from a little trial and error to get the best photo. So play around with different ISOs. And if you’re having to shoot with a high ISO and there’s a bit too much noise (or graininess) in your pictures, have a look at them in black and white instead.

Can we summarise this, please?

Quick recap

ISO refers to the sensitivity to light of film or the digital camera’s sensor.
The higher the number, the greater the sensitivity.
A low ISO generally offers the best image quality, and great for brightly lit situations.
A high ISO setting may be required to capture images in low light situations, but can cause noise to show up in your photos, especially at higher settings.

Thank you!

Now, go out and try some shots using different ISO settings, and in different situations. The practice will better help you understand ISO, and the results in your photos. Then you will be better prepared for any situation. You might also want to experiment with higher ISOs to create interesting twist to your shots!

Okay! I’m going out with my camera now.