How To Change ISO On Canon Cameras

Changing the ISO manually is a critical skill for photographers that want to hone in on their camera settings. 

Today we’re going to talk about how to change and control ISO on your Canon camera. This will be a step by step guide that will cover Rebel series cameras as well as more advanced cameras. 

Processes will be similar no matter what Canon DSLR or Mirrorless camera you have. 

Check out our article on how to change aperture on Canon cameras too. 

Step 1: Turn On Camera

First things first, turn that camera on. Ensure you have a charged battery so we can do plenty of shooting and test out our ISO settings once we control them. 

Step 2: Set Mode

On your camera mode dial, select any of the following modes:

  • [M] Manual Mode
  • [Av] Aperture Priority Mode
  • [Tv] Shutter Priority Mode
  • [P] Program Mode
Camechs - Custom Shooting Modes Explained

Only the above modes will allow you to select and adjust the specific ISO level. Other modes will simply put ISO in automatic mode. 

[B] Bulb mode also has manual ISO, but that is a setting that is only used for super long exposure photography. You will most likely be in one of the settings noted above if you desire some level of manual control. 

Step 3: Adjust ISO

So your camera is on and you’re in the right mode. We can now change ISO. 

The easiest way to change ISO is by using the dedicated ISO button on your camera if you have one. It will be a clearly labeled button. 

Find Your ISO Button

Most Canon cameras have this button on the top of the camera.

Sometimes you will find the ISO button is on the back as one of the direction pad buttons. If you see “ISO” next to it, that’s the correct button. 

Canon BG-E21 Review Camechs 7

Once you press that button, it becomes the only setting shown on your LCD. It is also the only setting that is shown in your viewfinder, or on your top LCD if you have one. 

Now you can either roll your index finger control dial next to the shutter, or press one of the directions on your d-pad. On the 6D Mark II, even the thumb wheel can be rotated to change ISO after you press the ISO button. 

And that’s it! Pretty simple right? 

The Q Button

If you want to use Canon’s Q – Quick Access button, you can do that as well. You do have to be using your camera’s LCD for this operation. 

The Q button basically lets you select from any of the available settings on screen. Even if you don’t use your LCD, the Q button will turn it on and let you browse through the main shooting settings. 

Canon 6D Mark II - Back Button Auto Focus - Q Button

Once you hit that Q button, scroll over to the ISO field. It is typically the setting at the top right hand side of the screen. All you have to do is hover over it, and then scroll your index finger control dial. 

If you do decide to ‘select’ the ISO setting, it will show you a full screen preview of ISO levels. 

What Is ISO And What Does It Do? 

Now that we have ISO under control, what does it do for us? 

Basically, ISO has one job and one main side effect. Its main job is to make your camera sensor more ‘sensitive’ to light. 

Increasing the ISO is the same thing as telling your sensor to collect more light. All of this ‘collecting more light’ does not come free though. 

A side effect of increasing ISO is that you get more sensor noise in your image. Sensor noise is generally undesirable in photography. The lower your ISO, the less sensor noise you get.

ISO Graphic

High end cameras are able to shoot at high ISO levels while keeping noise pretty low. You get what you pay for! 

Most entry level cameras can have pretty clean images up to ISO 1600. Beyond 1600 on affordable cameras usually needs some noise reduction work in post. Every camera is different however. 

High end cameras can go up to 6400 while still outputting usable images! There are some outliers though.

The Sony A7S is probably the best performing low light camera at the time of writing. It has this super power of maintaining detail at ultra high ISO levels

Variable ISO Image Samples 

Let’s take some dark images at various ISO levels with different cameras and see what it looks like. 

Today we’re going to use the Canon T2i and the Canon 6D Mark II.

Rebel T2i, ISO 100
Rebel T2i, ISO 3200
Rebel T2i, ISO 12800
6D Mark II, ISO 100
6D Mark II, ISO 3200
6D Mark II, ISO 12800

You can tell both cameras struggle at 12800, however the 6D looks good at 3200. The T2i still struggles a bit at 3200, but some of that noise might be recoverable with some post processing.

Why Is ISO Control So Important?

Manual ISO control helps you precisely balance your noise introduction and exposure goals. If you are shooting in low light situations, higher ISO levels will be more important. 

You should learn where your camera creates a usable image, and where it is simply limited. If your subject is still, you can always just introduce a tripod to increase shutter speed and reduce ISO. 

It all comes down to the exposure triangle. There are tradeoffs in three dimensions. Check out our article on the basics of photography exposure. We walk through the exposure triangle and all related tradeoffs.