Exposure in Photography: What You Need to Know

11 min readNov 22, 2020

What is exposure, and why do you need to understand it?
We’ve all been there: you shoot a bunch of photos in low light, or on a particularly sunny day, only to realize after you load them into Photoshop that your shadows are slightly too dark, or the sky is too bright, or the motion you wanted to capture is a little blurry. Mastering exposure will help you avoid classic problems like these.

The better you understand exposure, the easier it’ll be to get your photos looking how you want with only minimal edits needed.

Exposure might seem like a basic photo topic — in reality, it’s anything but. While the process of exposure in the camera isn’t too difficult to understand, perfect exposure can be challenging even for advanced photographers due to all the different elements at play.

No matter where you’re at in terms of photography skill level, it’s worth taking a deep dive into how exposure in photography works. This is a part of photography that you’ll keep perfecting over time.

Shot on Canon EOS 6D with 85.0mm lens and aperture of f/2.8, ISO 100. Understanding exposure will help you take perfectly-lit shots like these.

Photo by eberhard grossgasteiger · View Photo

The camera settings that impact exposure
Simply put, exposure is a measure of the amount of light hitting your camera, by reaching the sensor (or film, if you’re shooting analog).

A well-exposed photo ideally won’t be too bright or too dark, but will accurately depict the scene that was photographed. Of course, beautiful photos can also be made by intentionally playing around with exposure for a shadowy or blown-out shot — but let’s master the basics of exposure before we get into those creative uses.

There are three key settings on your camera that you’ll need to work with for accurate exposure. They are aperture, shutter speed, and ISO. These settings work together to change how dark or light a photo is, and the interplay between them is the challenging part of mastering exposure.

If only good exposure was as simple as thinking, “Okay, I’m shooting on a dark night, so I’ll crank up the exposure”! Okay, shooting in the dark does usually call for a wider aperture, faster shutter speed, and higher ISO, but you’ve also got to make sure you don’t make those settings too high. We’ll explain this in more detail below.

How does aperture work?
Check out the photo below — or take a close-up look at a camera lens if you happen to have one handy. You’ll see a series of overlapping elements: these are aperture blades. When you adjust aperture in your camera, you’re adjusting these blades, making the hole at the centre (known as the aperture) bigger or smaller.

The aperture blades in the lens are what makes the magic happen.

Photo by Pixabay · View Photo

Think about how your eyes work. When it’s dark, your pupils get bigger, allowing more light into the eye (in simplified terms) and helping you see better. When it’s bright, your pupils get smaller. The aperture of a camera lens works the same way. When your camera is setting aperture automatically, it’s a bit like your brain automatically working to constrict and dilate your pupils based on how much light there is.

As your camera’s “brain” isn’t quite as advanced as the human brain — yet! — there are some situations where the auto setting might not cut it. And just knowing how to set aperture yourself is extremely helpful in better understanding how exposure works.

Aperture can be a bit confusing to remember because a “higher” aperture number actually means a smaller aperture. What’s important to know is that aperture numbers are fractions. Different lenses will have different aperture options, but in general, the widest aperture begins at f/1.4, and aperture gets smaller with numbers like f/2.8, f/4, and so on, up until f/22 or even f/64.

For now, it’s enough to say that these numbers are simply how your camera measures the size of the aperture, but there is a more complex mathematical explanation you can read about if you’re so inclined.

Shot on Canon EOS 6D with 50.0mm lens and aperture of f/1.8, shutter speed 0.001s, ISO 100.

Photo by Rachel Claire · View Photo

Shot on Canon EOS 5D Mark III with 35.0mm lens and aperture of f/1.4, ISO 100.

Photo by Misael Garcia · View Photo

These photos are both great examples of how a wide aperture improves exposure in a dark setting. On the left, the model is backlit by a bright window in a fairly dark room. Using a wide aperture of f/1.8 allows lots of light into the camera, ensuring that the model’s face and clothing can be seen in detail. This would be much harder to achieve with a small aperture. In the photo on the right, a gloomy day is captured perfectly with another wide aperture of f/1.4. Both photos use a low ISO of 100 to amplify detail — we’ll explain ISO more later.

The photos here also demonstrate aperture’s major impact on depth of field. Depth of field describes how much of your photo is in focus. A large depth of field occurs when your whole photo, or most of the photo, is sharp. This can be best achieved with a smaller aperture. For a thinner depth of field, where only part of the photo is in focus, a wider aperture is helpful. Of course, you can also adjust depth of field through tweaking other settings, but aperture plays a crucial role.

Our examples above show how a wide aperture helps put a selective focus where it matters in an image. The photo of the city street focuses in on the pavement for a creative effect, blurring the traffic in the background. The image of the model uses a more subtle focus: her face and hands are the focal point, while the lower part of her body is slightly blurred.

As a final visualization to help you remember the best aperture settings, compare these two images below by Pexels photographer Ricardo Esquivel. They’re both shot in the same lighting on a Sony Alpha 7 III, using an 85mm lens and 0.02 shutter speed. The change is only in aperture and ISO.

We can see just how much change a large aperture (left) makes as compared to a small aperture (right). Although the small aperture and high ISO shot here captures a lot more detail, the result is a lot of noise and grain, while the large aperture image is smooth. In a lot of cases, you’ll want to aim for an image somewhere in between these two.

Aperture: f/1.4, ISO: 500

Aperture: f/16.0, ISO: 12800

The key to mastering aperture, once you understand how it works, is really trial and error. When shooting in dark conditions, you can experiment with first shooting on the widest aperture possible and then slowing decreasing aperture to balance keeping your image sharp and focused yet also properly lit. In bright settings, first try out your smallest aperture, and then increase the width and see what results. Over time you’ll start to learn what settings work best for your lens depending on the light.

How does shutter speed work?
Shutter speed is even more straightforward to understand than aperture. It refers to how quickly your camera takes a photo. The speediest shutter speeds are mere fractions of a second, while longer ones may go up to a few minutes, or even longer, depending on the camera. Most cameras generally only go up to 30 seconds of shutter speed, but some allow for more.

Adjusting your shutter speed works in tandem with aperture to create a perfectly exposed photo. As we’ve now learned, being able to let more light into your camera is crucial for illuminating detail in darker settings. Leaving the camera shutter open for as long as possible is another way of bringing more light into an image.

In general, fast shutter speeds can be useful when you want to capture motion in an image, whereas slow shutter speeds are good for images where there isn’t really any movement or where you’re in need of extra light.

Shot on Nikon D600 with 14.0mm lens and aperture f/2.8, 30/1s shutter speed.

Photo by James Wheeler · View Photo

Here, we see just how effective a long shutter speed can be for low light shots. This nighttime photo really shines with a 30 second long exposure. We see all the stars clearly, the moon is glowing, and the detail in the rest of the image is captured too. An aperture of f/2.8 also helps ensures the image is sharp.

Shot on Canon EOS 5D Mark II with 105.0mm lens and aperture f/5.6, 1/2000s shutter speed, ISO 400.

Photo by Clem Onojeghuo · View Photo

Shutter speed is important not only for exposure but also in capturing motion. This crystal clear photo of waves uses a quick shutter speed of 1/2000, recording the crest of each wave perfectly so that they appear still. A medium aperture of f/5.6 also helps in creating a wide depth of field so that the entire image is in focus.

Shot on Sony NEX-5 with 16.0mm lens, aperture f/2.8, 1/10s shutter speed, ISO 200.

Photo by Martin Dusek · View Photo

In the photo of the waves, a super fast shutter speed helped freeze motion in the frame. In this highway photo, a slower shutter speed allows the photographer to create an impactful blurred effect, so that only the lights of the cars stand out.

How ISO can be the final step to perfect exposure
You might have noticed that many of the photos featured here have a 100 ISO — but not all. 100 is usually the base ISO for most cameras, and keeping it that way is often fine for many shots. But sometimes, when you’re shooting in difficult conditions or trying to achieve a very specific result, ISO can really be a lifesaver.

What is ISO, exactly? Changing the ISO setting on your camera doesn’t actually change how much light is let in as you snap a photo. Instead, ISO changes how bright or dark your photo appears in-camera, digitally adjusting the image after light has already reached the sensor. Higher ISOs can really help you capture detail when shooting motion or dark scenes.

You may find it useful to think of ISO as a last step in setting up the perfect shot. Once your aperture and shutter speed are set, you might find you still need additional light in your shot, and this is where adjusting the ISO comes in handy.

The one drawback with ISO is that it tends to add a lot of grain to your photos. Basically, the higher the ISO, the brighter the photo, and the noisier. After the base ISO of 100, ISO typically increases to 200, 400, 800, 1600, 3200, and 6400, with some cameras even going higher.

Shot on Canon EOS 1100D with 18.0mm lens and aperture f/3.5, ISO 6400.

Photo by Tobias Bjørkli · View Photo

This Northern Lights photo is the perfect example. Using a very high ISO of 6400, the photographer is able to show every detail of the scene, from the snow-covered trees to the stars in the sky. As the ISO is so high, we also see a lot of grain in the image; but with a lower ISO, we would lose that detail. An aperture of f/3.5 allows for a broad depth of field that keeps both the sky and the foreground in focus.

The end result is a beautiful shot — we think the grain adds an interesting texture rather than detracting from the image. When shooting in dark conditions like these, you’ll have to decide how much grain is acceptable in your shots.

We’ll finish off by contrasting that nighttime capture with a different, lower ISO one. Here, the photographer uses a fairly low ISO of 320 to focus on the brightly illuminated tent, allowing the trees to provide a silhouetted frame for the photo. At the same time, a high aperture of f/2.0 allows him to capture lots of light: even the stars in the sky.

Shot on Canon EOS 6D with 35.0mm lens and aperture f/2.0, ISO 320.

Photo by Josh Hild · View Photo

In conclusion: Mastering exposure for beautiful photos
We’ve covered the basics of how exposure works, including understanding aperture, shutter speed, and ISO. As we discussed earlier in the aperture section, practice is really what makes exposure perfect. You’ll want to try experimenting with all of these elements of exposure to achieve even better shots.

We haven’t included super specific recommendations for exposure settings apart from the examples here because it really depends on your own camera, lens, and the setting you’re in. Now that you know how all the elements of exposure come together to bring light into a photo, you’ll be able to play around with these settings for expertly-lit images no matter where you’re shooting.

Exposure in Photography: What You Need to Know

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