What Is ISO In Photography? – The Complete Guide For Beginners

Last Updated:

As you begin to learn how your camera settings work, you still may be unclear about what ISO does for your photography. ISO is the third key pillar of exposure in photography and plays a more significant roll in the photos you take than you might think!

In this article, you’ll discover the importance of ISO in photography, how to best use it, and some tips to avoid going overboard with your ISO settings. If you’re new here and haven’t seen the previous posts in this beginner photography settings series, make sure to check out the best camera settings for beginner photographers, understanding shutter speed, and why aperture matters in your photography.

One last thing before I jump into everything you need to know about ISO in photography, make sure to grab your Manual Mode Cheat Sheet to use as your handy reference guide to perfect camera settings where ever you go! You can click here to get access to the free Manual Mode Cheat Sheet. It’s amazing to help memorize ISO settings so you won’t want to miss this one!

What Is ISO In Photography

ISO is one of the three primary camera settings that affect the exposure (aka brightness) of your photo. When you adjust your ISO setting, you’re actually changing how sensitive your sensor is to light. The more sensitive the sensor, the brighter your photo will appear!

ISO is a fantastic tool to help balance out your exposure after you’ve set your shutter speed and aperture for the scene you are shooting. Changing your ISO can often give you that little bit of brightening or darkening needed to really make your photo pop.

Luckily, the ISO settings are straightforward to understand. As the ISO number increases, so does the brightness of your photo. Most digital cameras will have ISO’s ranging from ISO100 to ISO6400. Higher-end camera models can have ISO ranges far beyond that.

Where To Find Your ISO Setting On Your Camera

Your ISO setting can be found within your settings preview. It’s most commonly labeled with the word ISO in a small box, followed by a number ranging from 100 to 6400 for example. This number is the ISO sensitivity.

Digital ISO Vs. Film ISO

ISO in digital photography is a little bit different than is on film cameras. As you’ve now learned, the ISO setting in digital photography affects how sensitive the camera sensor is to incoming light. However, the ISO on a film camera is how sensitive the film is to light. The higher the films ISO, the larger the film grain will appear.

Now you may be thinking, “sweet, digital ISO means no film grain!”, and although you aren’t totally wrong, there’s a little more to the story. The caveat to ISO in digital photography is as you increase your ISO, you brighten your photo, but also increase the amount of noise in the image. I’ll talk more about noise later in this article.

With film cameras, the ISO cannot be adjusted since it’s the sensitivity of the physical film. With digital cameras, ISO can be easily adjusted up or down since it’s only affecting the sensor and not a physical roll of film.

What Does ISO Stand For

ISO stands for International Standardization Organization. This is an organization that standardizes the sensitivity of camera sensors across all brands (among many other things). Although certain camera sensors may have less noise at equivalent settings, the increase of brightness between ISO settings are the same across all cameras.

The Downside To  ISO

ISO can seem like the perfect camera setting. It’s straightforward to operate, there’s no fancy lingo, it just brightens your photo, what more could you ask for? Although those are all great perks of ISO in photography, there is an obvious downside you’ll discover at higher ISO’s.

As you increase your ISO, the more noise will appear in your photo. Noise looks a little bit like static on an old TV screen. It’s not very stylistic and can often be a little distracting. Not only that but it can also take away from the overall quality of your photo. Unfortunately, digital noise doesn’t quite have the same aesthetic effects as film grain, so it’s not commonly favored by most digital photographers.


This isn’t to say that you should be afraid of using a high ISO setting. It’s just important to remember that as you increase your ISO, so will the amount of noise in your photo. Try not to go crazy with your ISO when you could likely make adequate exposure adjustments with your shutter speed or aperture settings!

What Does Noise Look Like In A Photo

The amount of noise in your photo very slowly increases with each ISO setting. Below are some visual examples of how much noise appears in a photo from the lowest to highest ISO. Notice the significant loss in quality, particularly in the sky.


How To Use ISO In Photography

Learning how to use your ISO is an integral part of learning how to shoot in manual mode. It’s an essential tool to balance out the exposure in your photos but needs to be used purposefully.


It’s always best to keep your ISO setting as low as possible. It’s good to use a low ISO because it makes for a better-quality image! If you’re shooting in daylight, there is rarely a reason to use a high ISO setting, even if you’re in the shade. You can always open up your aperture or slow down your shutter speed to lighten up your exposure instead. Remember, you want to keep your ISO setting low to reduce the amount of noise in your photo!

Now, there are a few exceptions that you’re going to need a higher ISO for. For example, astrophotography or very low-light scenes require you to use a higher ISO setting. Since there is such a lack of available light in these types of scenes, increasing the ISO helps you to utilize every last bit of light to help capture all the details possible.


What Is Auto ISO?

The 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 of 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 Auto ISO 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 settings screen.

light meter in photography, beginner photography tips

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 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 is 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 will automatically select ISO values to best suit the exposure of every shot you take.

ISO Quick Tips & Review

Your ISO Capabilities Will Depend On Your Camera

Depending on the camera you are using, the ISO range available to you can change. The standard ISO range is ISO100 to ISO6400, but with certain camera models, you can get up to something like ISO409600.

The Amount Of Noise Will Depend On Your Camera

Not all cameras have the same amount of noise at the same ISO settings. It all comes down to the actual sensor’s capabilities. Typically, higher-end cameras will have less visible noise at higher ISO’s compared to more entry-level camera bodies.

Don’t Be Afraid Of Using A High ISO

Sometimes, the scene you are shooting requires using a high ISO. Don’t miss out on a shot because you’re afraid of using the wrong ISO setting. Try to keep it as low as possible when you can, but don’t be scared to utilize it when the time comes.

ISO Is A Great Tool To Help You Balance Your Exposure

Once you’ve set your shutter speed and aperture, sometimes your photo still needs a little bit of help to get the perfect exposure. With your ISO, you can boost your exposure to a more even level.


Learning to use ISO in your photography is a big part of discovering how to nail your camera settings. ISO is a great tool to help balance out your exposure or give you a little bit of extra brightness in darker scenes. It’s crucial to remember that ISO not only brightens your photo, but it also can add noise to your image at higher ISO’s. You shouldn’t be afraid of this extra noise, but it’s essential to stay aware of and consider it before you snap a photo!

If you know someone who needs to boost their ISO knowledge, then make sure to share this post with them! If you enjoyed this article and want to keep up to date with more weekly photography content, make sure to subscribe to my weekly email newsletter!

Happy Shooting!


Photo of author
I'm a Canadian photographer and photo retoucher turned founder of bwillcreative.com. Around here I help you to decode the mystery of photo editing with no-fluff videos and written guides to help you achieve your creative goals. Outside of shooting photos and my passion for educating, you'll find me mountain biking or on the trails with my dog, Sunny!

Continue Reading:

How To Fill A Selection In Photoshop (5 Best Ways)

Learn how to fill anything in Photoshop from selections, shapes, and text with solid color, gradients, and even images!

How To Use The Eraser Tool In Photoshop (Complete Guide)

Learn how to use the Eraser Tool, Background Eraser Tool, and Magic Eraser Tool in Photoshop to remove unwanted areas of any layer.

How To Invert A Selection In Photoshop (Step By Step)

Learn the importance of learning to invert a selection in Photoshop with the help of simple keyboard shortcuts and several other methods.

What Are Embedded Previews In Lightroom + How To Use Them

Use this guide to help you understand the use of embedded previews in Lightroom along with tips to help you use them in your workflow.

Adobe Lightroom System Requirements For Mac & PC

Here's a breakdown of the system requirements for Adobe Lightroom Classic and Lightroom CC to make sure it will run smoothly on your computer.

How To Add A Watermark In Lightroom Classic & CC

Learn how to add a text or graphic watermark to a photo in Lightroom Classic and Lightroom CC to protect your photos from theft.

How To Make A Background Transparent In Canva

Learn how to create and export images with transparent backgrounds in Canva to open up more design options and creative styles.

How To Use Frames In Canva (Ultimate Guide)

Here's how to use frames in Canva to creatively add image elements to your designs in just a couple of clicks.

How To Make A Table In Canva (2 Easy Ways)

Learn the ins and outs of how to make a table in Canva along with tons of customization options to make your table look perfect!

Notify of
Newest Most Voted
Inline Feedbacks
View all comments

[…] in Luminar 4. This filter allows you to reduce the amount of grain in your photo from using a high ISO. It smooths this noise to help improve the overall quality of your image. The same sliders are […]

[…] in your photos when shooting in low light situations. Primarily when you’re using a high ISO or significantly boosting your shadows in post is when noise will start to overrun your […]

[…] than cranking the ISO or opening the aperture too much, a tripod will help you choose better […]

[…] freedom to use a slower shutter speed. That way, you’re never sacrificing depth of field or ISO to get the […]