How To Choose An ISO Setting: The Basics

DSLR for Beginners, DSLR Photography

how to choose an iso settingIn this post, you'll learn how to choose an ISO setting.

Choosing an ISO setting basically comes down to two things:

  1. the light you're working with, and
  2. the type of shot you're after.

Low light requires a higher ISO setting. You might also want to adjust the ISO for action shots and shots taken without a tripod.

ISO is one of the three fundamental things you need to learn in order to get creative with your photography. (The other two are aperture and shutter speed.)

Playing with the ISO settings can help you learn a lot about how your camera works.

While ISO is fun to experiment with, I usually let my camera choose it automatically. You'll see why later on in the post.

What Is ISO?

ISO stands for International Organization for Standardization, or International Standards Organization.

The ISO setting on your digital camera allows you to control its sensitivity to light, it measures the sensitivity of the image sensor in your camera. The lower the light, the more sensitive your camera needs to be to capture the shot you're after.

Remember these two things:

  1. The lower the ISO number, the less sensitive it is to light.
  2. The higher the ISO number, the more sensitive it is to light.

Each step up in ISO number, doubles your cameras sensitivity to light. It also allows you to capture a photo faster.

An ISO of 800 is eight times more sensitive than an ISO of 100. This would mean that if your camera was set at an ISO of 800, it would be 8 times faster at capturing an image than if it were set at ISO 100.

How To Choose An ISO Setting

Deciding how to choose an ISO setting all comes down to light and motion.

The more light you have available the lower ISO setting you should use to get a crisp, high quality photo.

The exception to this rule is if you want to freeze action. As mentioned above, the higher your ISO the faster your camera will take the shot. So to freeze action you are going to need to go with a higher ISO, or your action will come out blurry.

In the first picture (below) I was using a lower ISO so the water is a little more blurry. In the 2nd and 3rd picture I kept the ISO at 800 which allowed me to “freeze” the water.

motion freeze by setting iso

ISO 200, f/8.0, shutter speed 1/160

freeze motion with high iso setting

ISO 800, f/11, shutter speed 1/320

how to choose an iso setting

ISO 800, f/18.0, shutter speed 1/640

As I took these pictures, I set the ISO and let the camera take care of the aperture and shutter speed. Notice how those settings changed in the first two pictures as I adjusted the ISO, and then again in the 3rd, as I zoomed in.

By reviewing the settings chosen by your camera, you can learn a lot.  For example, the shutter speed in the pictures with the ISO of 800 is faster, so that tells me that shutter speed also has something to do with freezing motion. As the ISO goes up the camera becomes more sensitive to light, so the shutter does not need to be open for as long as it does when the camera is less sensitive.

Higher ISO to Reduce Camera Shake

If you are shooting without a tripod, a higher ISO will help reduce camera shake in your image. A handheld camera is in motion, even if it is ever so slight, so if you can capture your shot faster there is less chance of seeing blur from camera shake in your shots.

adjust iso for motion freeze and low light

Playing with the ISO during this shoot. I couldn't get very close because of the splashing water, but I wanted to get the light shining through it. Bryan took this shot with a GoPro

Choosing a faster shutter speed will also help reduce camera shake. I prefer adjusting the shutter speed rather than the ISO.

You can also reduce camera shake by going with a lower aperture setting, just remember that lower aperture settings change the depth of field, so closer objects look clear while the background will be blurry.

You may also want to choose a higher ISO setting in low light to make the most of the light available.

Why I normally don't like to adjust the ISO…

The higher the ISO setting, the more grain (noise) you will see in your photos. Some of that noise can be softened when you edit your photos, but it's usually best to have the least amount of grain possible.

To eliminate noise and capture the highest quality photos, it's always best to use the lowest ISO setting you can. For that reason I usually choose to freeze motion by controlling the shutter speed (speeding it up) and letting the camera deal with the ISO. I find that the camera is pretty good at choosing an appropriate ISO. Shooting inside in low light (without a flash) might be one of the times I would manually adjust the ISO.

Knowing how to choose an ISO setting will come from playing with the settings in various conditions, and then examining your results.

How To Adjust The ISO Setting

To adjust the ISO settings you push the little button (seen here on my Canon camera) that says ISO. When the ISO screen comes up, turn the little black dial in front of the ISO button.

set the iso on your camera

iso screen on camera

As you turn the little black dial in front of the ISO button you will see a different ISO option highlighted

iso setting on camera screen

The ISO is at 400. You will see that number change as you choose a new ISO.

When experimenting with ISO, it's easiest to just let the camera take care of aperture and shutter speed for you.

Keep in mind that if you set the ISO it will not change until you reset it, or set it to auto. So if you want to shoot in Aperture priority or Shutter priority mode, you'll want to make sure ISO is on auto, unless you want it on a specific setting.

How do you determine how to choose an ISO setting? Please share your tips by commenting on this post.

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Hi, I'm the Author!

I'm an amateur photographer and Canadian entrepreneur. Since moving to South America in 2009, we have made our living as content creators. I'm a partner at Storyteller Media, a content marketing company for Canadian travel brands. I am co-founder of this site, and our Nova Scotia travel site WiseGuides.ca.

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