How Does Your Camera’s ISO Setting Affect Your Photos?

Dann Albright 08-08-2016

Camera settings can be a bit esoteric, and ISO is one that a lot of people don’t really understand. But knowing when to adjust it can make a huge difference to your photography. Automatic mode will make adjustments for you, but learning to adjust ISO yourself is a big step toward taking full control of your camera.


What is ISO?

Let’s get a really common question out of the way: ISO doesn’t stand for anything. Or at least anything useful. The International Standards Organization (ISO) has a standard for measuring film sensitivity, and that’s what determines the ISO value of a particular photo (just like ISO images How to Create an ISO Image of Your Windows System Need to backup and restore Windows without backup tools? It's time to learn how to make an ISO image of your Windows PC. Read More ; they’re named the same way). The calculation of the ISO value is really complicated, but you can read all about it on Wikipedia if you want to know more.


To greatly simplify the definition, ISO is how sensitive your camera is to light. A camera that is highly sensitive will pick up more details from a dark scene than one that’s less sensitive. However, this increased sensitivity comes with a cost; you get a lot more “noise,” or seemingly random visual distortion. It’s a lot like film grain in old film photos. With a high ISO, you trade some image quality (in the form of increased noise) for increased detail in a dark scene.

You can see this type of noise in the image below (this is significantly zoomed in; you usually won’t see it quite this clearly in a full photograph).



ISO isn’t the only culprit when it comes to noisy photos; sensor size 6 Things to Consider When Buying Your First DSLR Camera With so many options out there, how do you choose the right DSLR for you? Every camera has so many specs and features that it's hard to tell them apart. Read More , shutter speed, and other factors also come into play, but your camera’s sensitivity is the main determining factor. Getting the proper ISO will help you take pictures that capture a lot of detail without introducing too much noise. It’s a bit of a balancing act, but with some practice, you’ll get really good at choosing the right ISO for every photo.

Some General Guidelines

It’s tough to give specific ranges for ISO, as the proper sensitivity depends on the light in your photo. But there are a few things you can keep in mind while setting up your shot that will help you get the clearest, most detailed images possible.

Use as low an ISO as you can. Jamming the ISO up as high as possible will certainly let you capture the most detail in very dark parts of your photo, but it will also add a lot of grain to other areas of the image and could cause the lighter sections to become totally blown out.

Compensate with slower shutter speeds. If you’re having trouble capturing the amount of detail you want in a scene, instead of bumping up the ISO, try opting for a slower shutter speed 4 Common Shutter Speed Mistakes That'll Ruin Your Photos When learning photography, you need to understand the essential rules of exposure. Here are some common shutter speed mistakes and how to overcome them. Read More first. Even if you just go up to 1/60, you might be able to keep the shutter open long enough to get the required amount of light for a good photo.



Use a tripod. This is good advice for photography in general, but it’s especially useful when you’re capturing low-light photos and you don’t want to add noise in the form of grain. If your ISO is getting to the 800+ range, consider backing it down and using a tripod Everything You Need to Know About Choosing the Perfect Tripod A tripod is one of the most important accessories for your camera - but how do you know which one to choose? In this article we explain everything. Read More with a shutter speed of 1/25 or slower instead.

High ISO is useful for quick shots. If you’re trying to capture something that’s moving fast or happening over the course of a fraction of a second (think blowing out candles on a cake), a high ISO is going to be useful, as it allows you to get a quick shot without sacrificing too much detail.

Don’t get in trouble with flash. Many places, like museums and churches, don’t allow flash. If you still want to get good shots, you might need to turn up your ISO. The photos might be a little grainy, but it’s often better to capture a grainy photo than nothing at all!


Some Examples of ISO

To give you an idea of how you might want to adjust your ISO, I’ve included a number of photos that have different ISO values. This should help give you an idea of how to think about ISO and the other factors that affect it.


The image above was shot at ISO 400, which is pretty low for a photo this dark. However, the shutter speed was 1/6, which is very long. You’d need a tripod for this long of an exposure. You’ll notice that there’s not a lot of noise in the photo — the black background is very uniformly black. The lower ISO setting for this picture helped in creating a nice, smooth background without distortion.



If your subject is in motion, and you don’t want to blur the photo, you’re going to need a faster shutter speed and, if you’re working with low light An Illuminating Guide to Low Light Photography If photography is about capturing light, how do you take photos when light is scarce? Read More , that means you’ll want a correspondingly high ISO. The image above was created using an ISO of 3200 and a shutter speed of 1/13, which is still fairly long. Because of the very dark scene, however, a higher ISO enabled the photographer to get more detail in the photo without motion blur.


On the other side of the spectrum, we have the picture above. This scene has plenty of natural light, so the photographer used a very low ISO of 50. The shutter speed was 1/160, which let in just enough light to prevent the highlights from being blown out.


Even when you do have plenty of light — such as at this track meet — you might have to bump up your ISO a bit. To keep these runners from being blurry, this photographer used a shutter speed of 1/2000, which doesn’t let much light into the sensor. To compensate for the quick shutter speed, he used an ISO of 200. Not very high, but higher than the previous photo.

East Wing of the Ontario Legislative Building

The photo above was taken with an ISO of 800, which is starting to get into the “dangerously high” range. However, because the picture was taken without flash and the scene is quite dark, the increased ISO is warranted. It’s possible that flash wasn’t allowed in this building, leaving an ISO increase as the only option for capturing the scene.

Start Practicing

Like anything else in photography, the best way to learn about ISO is to play around with it 7 Skill-Building Photography Exercises That Really Work Anyone can take a photograph, but taking a great photograph? Difficult. These photography exercises actually work. Read More . Take the same picture with several different ISOs and see what happens. Try turning it way up, try turning it way down, and compare the results. Eventually you’ll learn to fine-tune your ISO so you get the best exposure every time.

Do you use the ISO settings on your camera? Or are you intimidated by this setting? How have you practiced using it in the past? Share your experiences and tips in the comments below!

Image credits: photoschafl via Flickr, Lauri Heikkinen via Flickr, Tim Bartel via Flickr, Ron Lute via Flickr, Billy Wilson via Flickr.

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  1. wayne
    August 12, 2016 at 12:14 pm

    This is a great summation of iso. Greatly extended my understanding. Practical.Thanks!

    • Dann Albright
      August 16, 2016 at 2:20 pm

      Really glad you found it useful! I learned about ISO settings in a workshop once, and it was one of the things that really stuck with me. It's been a hugely useful thing to know about!