What Is Auto ISO And How To Use It In Your Photography

Automatic ISO is widely used by both professional and beginner photographers alike. Rather than having to manually adjust your ISO for every photo, your camera does the work. Although this setting isn’t meant for every photo you take, it can offer a lot of advantages. Let’s talk about when you should use Auto ISO, and how it plays a roll in your photography!

What Is ISO


Before you can figure out what auto ISO does, you need to first understand what ISO does as a whole.

Your ISO setting is one of the three pillars of exposure that are crucial to every image you take. It directly controls the sensitivity of your camera’s sensor to incoming light. The more sensitive your sensor, the brighter your photo!

If you took away the ISO setting, it would be more challenging to manipulate the exposure of your images.

Unlike the shutter speed and aperture, your ISO setting doesn’t require much technical knowledge. The higher the ISO number, the brighter your image will be. It’s as simple as that.

For example, ISO 100 is the lowest setting on most digital cameras. With this setting, your camera will be the least sensitive to incoming light.

Using a low ISO setting like this is useful when taking photos in brighter environments such as the middle of the day or golden hour.

So what about in low light or complete darkness?

In low light situations, using a higher ISO setting will brighten your photo significantly. This will allow you to use a more favorable aperture and shutter speed to suit the style of your photo.

The max ISO setting across most cameras is ISO 6400. With this setting, the sensor is extremely sensitive to light and will help boost the exposure of your picture.

Depending on the camera brand and model, ISO ranges can go between ISO 100 to ISO 102400. Although there is a wider range, that doesn’t necessarily mean you want to use them.


The trouble with higher ISO’s is that it increased the amount of noise in your photo. Noise looks a bit like the static on an old TV screen and can reduce the quality of your images.

Luckily there are a variety of ways you can avoid noise in your photography that I share in this post.

Ultimately, ISO is a way to balance out your exposure after choosing your shutter speed and aperture settings. Learning how to balance these three pillars of exposure is a crucial part of mastering your camera settings.

To help you understand each of these settings in relation to ISO, the exposure triangle is a useful resource. This triangle shows the relation between each pillar of exposure and how it affects your images.

You Might Like: Understanding ISO In Photography

What Is Auto ISO

Auto-ISO-In-PhotographyThe auto ISO setting will automatically choose an ISO best suited for the exposure of each photo you take. Auto ISO is found across the majority of digital cameras and can be used in a variety of camera modes. Although it’s relatively simple to understand this setting, it leaves you with two main questions:

How does auto ISO work?


Should you use auto ISO in your photography?

The reason it’s so useful is that it will quickly fine-tune your exposure without any manual input. The reality is, you don’t often need to change your ISO setting dramatically.

When you’re shooting outdoors on a bright sunny day, you’ll likely stay between ISO 100 – ISO 500.

This isn’t much a shift but it can be annoying to swap back and forth between. As a cloud covers the sun or you start shooting in the shade, suddenly you may need to change the ISO setting.

With the help of auto ISO, your camera will make those adjustments for you. Whenever you’re shooting in inconsistent lighting conditions, using auto ISO can save you a bit of time.

– How This Setting Works

Like other automatic settings, auto ISO works by making exposure adjustments based on the internal light meter. Your camera’s internal light meter is a key tool to help you find the right camera settings. It can be found when you look through your camera’s viewfinder or on your setting screen.

light meter in photography, beginner photography tips

An example of a light meter.

The light meter works by metering incoming light and predicting the exposure of your photo with the current settings. In an ideal world, your light meter would read as close to the middle (aka 0) as possible.

When using the auto ISO setting, your camera will try to change the ISO value to improve your exposure. For example, if your light meter was reading as 1 stop underexposed, your camera would choose a higher ISO setting. This would brighten your image and bring your light meter reading closer to 0.

If your light meter was reading as 1 stop overexposed, your camera would automatically set your ISO to the lowest setting. For most cameras that would be ISO 100.

Although your photo will still be too bright, the auto ISO setting is doing all it can do to darken your photo.

Fortunately, as the lighting conditions change, so will the light meter readings. Auto ISO works to balance out your settings to best suit any changes in the environment.

– Should You Use Auto ISO?

For many beginners, it can be challenging to decide if you should use Auto ISO or not. Even though it has it’s advantages and is easy to use, it’s not recommended for all kinds of photography.

This setting should be used in situations where you’re capturing action and aren’t set up on a tripod. Any type of photo where you want to quickly capture something and move on to the next thing.


When a lot is happening, Auto ISO lets you move quickly between shots.

Especially when used alongside semi-automatic camera settings, you gain the ultimate balance between creative intent and speed. Photography genres such as sports, wildlife, or events are prime examples of when you should use an auto ISO.

Of course, you can get by without an automatic setting in these genres, but it will sure help!

In situations where you aren’t pressed for time, using auto ISO isn’t as beneficial. For example, with landscape, architecture, or night photography you have time to set up, use a tripod, and compose your shot.


Auto ISO is not necessary at night.

Auto ISO isn’t necessary when you can manipulate your camera settings to keep a low ISO. The lower your ISO setting, the less noise will be in your photo. Even in low light, you could use a slower shutter speed or wider aperture rather than increasing the ISO.

It’s not ‘wrong’ to use auto ISO in any of these situations, but it may choose a higher ISO than necessary.

How To Use Auto ISO

Learning how to use Auto ISO is easy since all you need to do it select it and the camera does the rest! Under your ISO settings, choose the option that reads ‘AUTO’.


Selecting this is all the work required to use this setting. From here your camera with automatically select ISO values to best suit the exposure of every shot you take.

The Best Camera Modes For Auto ISO

Automatic ISO can be used across all camera modes. Here are the best camera modes to use it with:

– Aperture Priority Mode (Av or A)


Aperture Priority lets you manually choose the aperture setting while your camera does the rest. You can manually choose the ISO settings if you wish, but auto ISO is a valuable addition to this camera mode. That’s because it gives you fully automatic settings, with the creative control of depth of field. 

– Shutter Priority Mode (Tv or S)


Shutter Priority allows you to manually set a shutter speed while your camera chooses the rest. This is extremely useful to reduce motion blur and get crisp action shots. Using the auto ISO setting lets you rest easy knowing you’ll have the right exposure no matter the shutter speed.

– Programmed Automatic (P)


Programmed Auto Mode basically does all the same things as Automatic Mode but with more customization. In this mode, you gain access to other useful settings such as white balance, metering modes, focus points, and picture profiles. If you still want fully automatic settings, but with more customization, using Programmed Auto with auto ISO is a great combo.

Read More: How To Choose The Best Camera Mode For A Photo

Does Auto ISO Work With Manual Mode?

Yes, you can use auto ISO in Manual Mode. You can turn it on or off simply by selecting it in your ISO settings. This way you can have fully manual camera settings, without needing to think of your ISO.

However, using auto ISO in Manual Mode doesn’t necessarily make a lot of sense. The reason you’re using this mode is to get the most control out of your camera. So why use an automatic setting?

If you want to speed up how fast you set up your camera for a photo, opt to use a semi-automatic camera mode instead. Save Manual Mode for when you have a very specific creative intent for your photo!

The Best Types Of Photography For Auto ISO

– Sports & Action Shots


Auto ISO is incredible for any type of photo with a lot of movement. Especially with Shutter Priority, all you need to focus on is your shutter speed. Auto ISO will sort out the rest to get you a proper exposure in every shot.

– Wildlife


Animals aren’t going to keep still while you get your settings right. Using auto ISO gives you one less thing to do before you take a photo. It may not seem like much, but it will save you some time while setting up!

– Events


Whether it be corporate events, weddings, or concerts, the lighting conditions are constantly changing. Using auto ISO will help to keep your exposures more consistent as you move between spaces during your shoot.


Although auto ISO is a very simple setting, learning when you should use it is more complicated. The location, style of photo, and amount of time you have will all impact whether you use this setting. Overall, it’s a great way to speed up the shooting process and will help keep your exposures more consistent.

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