Facebook Pixel Making Sense of the Exposure Triangle – ISO, Aperture, and Shutterspeed Made Simple

Making Sense of the Exposure Triangle – ISO, Aperture, and Shutterspeed Made Simple


Ever hear other photographers talking about shooting in manual mode, and using terms like ISO, aperture, and shutter speed and have no idea what they’re talking about? Then this article is for you. While making sense of the Exposure Triangle may seem overwhelming, you’ll learn everything there is to know so that you can get shooting in manual mode quicker!

Image: Canon 6D, 28mm, f/5.6, 1/250, ISO 400

Canon 6D, 28mm, f/5.6, 1/250, ISO 400

Everything in photography has to do with light

All three settings in photography, ISO, aperture and shutter speed are collectively called the Exposure Triangle. They work together to allow you to get the exposure you want in your image. Use these together to control the camera fully to suit your creative direction.

If you have a perfect exposure, and you change one of these elements (ISO, aperture or shutter speed), you’ll invariably have to change another to make up for that change.

So, let’s break down what each of these factors mean.


What is ISO?

When making sense of the exposure triangle, you first need to understand ISO. ISO is related directly to the way your camera’s sensor handles your exposure. Your camera’s sensor is light sensitive, but the amount of light applied to the sensor itself happens via Shutter speed and Aperture.

ISO is the electrical signal amplification from the sensor that is applied post-exposure. When you have a low ISO number, less amplification gets applied. Alternatively, when you use a higher ISO number, more amplification gets applied.

It’s this level of amplification that can make digital noise more obvious. These noise points already exist in the image, but they are faint. Extending your ISO magnifies this noise to become more apparent in your image.

Image: When it’s particularly bright outside, like in this photo, use a lower number ISO becau...

When it’s particularly bright outside, like in this photo, use a lower number ISO because there is plenty of light.  Camera settings: f/5.0, 1/800, ISO 200, 85mm shot on Canon 6D.



ISO is measured in numbers ranging from 50 to 25,600 on some models. There is usually a button on your camera that is labeled ISO. This is where you’ll be able to change the ISO depending on the lighting situation.

Image: Here, we used auto mode to get an idea of the exposure we would need to take a photo of these...

Here, we used auto mode to get an idea of the exposure we would need to take a photo of these stuffed animals setting the ISO at 100.

Image: As you can see in this photo, using a high ISO made the image brighter than we needed.

As you can see in this photo, using a high ISO made the image brighter than we needed.

Using a higher ISO can help you in low light situations when you want to keep a relatively fast shutter speed to avoid camera shake. However, you need that boost in light to help expose correctly.

Image: When you use a high ISO, your camera magnifies digital noise – little points on your image th...

When you use a high ISO, your camera magnifies digital noise – little points on your image that make it look grainy.


When making sense of the exposure triangle, you need to understand aperture next. Aperture, is the opening and closing of the lens. Measured in F-numbers, it affects both the amount of light entering the camera, and the depth of field in your image.


Camera settings f/2.5, 1/100, IS0 400, 50mm. In order to get the baby’s hand in focus and nothing else, we had to use an open aperture of f/2.5.

The depth of field is how much is in focus from foreground to background. A lower f-number will open your lens and let more light in, but it will also give you a narrower focus range (a shallow, or small depth of field). While a higher f-number will close your lens, and lessen the light entering, it will give you a wider focus range (a wide, or large depth of field).


This is especially important to keep in mind when taking portraits so that you can determine how much you want in focus.

For an individual portrait, any f-number between f/2.8 and f/5.6 works great. You still have your subject in focus but you do get some bokeh (blurry background due to a low f/number).


Here we have a more open aperture and therefore less is in focus.

For groups of people, you’ll want a high f-number like f/8 or f/11 because, at a lower f/number, you have less depth of field. This means your plane of focus is narrower. If you have people standing outside the plane of focus, they will be blurry. Therefore, in order to have everyone in focus, a high f/number is best because it gives you a wider plane of focus.


Here we are using a closed aperture, allowing more to be in focus.

Again, opening and closing of the lens affects how much light enters the camera. Eventually, in manual, you’ll have to compensate with one of the other two settings to make up for the lack of light or excess of light entering your camera.

Image: To capture the bird and the landscape surrounding it, we used an aperture of f/9. Other camer...

To capture the bird and the landscape surrounding it, we used an aperture of f/9. Other camera settings are ISO 400, 1/250, at 28mm.

Use Av or A mode on your camera to play with aperture. The camera will set the shutter speed for you to maintain correct exposure. However, you’ll be able to see a noticeable difference in your depth of field and in light entering your camera.

Shutter speed

When making sense of the exposure triangle, shutter speed is the next thing you need to know. Shutter speed dictates the length of time that the shutter is open.

Image: To get a silhouette, you’ll likely use a faster shutter speed to make up for the fact t...

To get a silhouette, you’ll likely use a faster shutter speed to make up for the fact that you are shooting directly into the light. This image has a shutter speed of 1/1000, f/16, ISO 400, 28mm.

Shutter speed is measured from seconds to fractions of a second (slow to fast shutter speeds). The slower the shutter speed, the longer it stays open to capture light. The faster it opens and closes, the less light is captured to make your photo.


For example, on a really bright afternoon, use faster shutter speed in order to create a good exposure. In a low light situation, like a nighttime scene or a dark cafe, a slower shutter speed can help capture enough light to make the photo.


In these two photos, we only changed the shutter speed and kept the other camera settings the same. You can see a significant difference in light.

Keep in mind, the slower the shutter speed, the more chance of camera shake occurring. Camera shake is an accidental blur due to the camera shaking, either in your hands, or due to some other force.

At slower shutter speeds, you are more likely to get camera shake. At faster shutter speeds this isn’t a problem as the camera opens and closes too quickly to register the shake. This is also dependent on the focal length of your lens. This is where the reciprocal rule comes into play. The rule states that 1/focal length of your lens is a good place to start to avoid camera shake. For example, if you have a 100mm lens, then you would need a shutter speed of 1/100 sec minimum to avoid camera shake. Read more about it here.


Using a slow shutter speed can give you interesting images with movement. Camera settings f/6.3, 1/13, ISO 400, 50mm.

Shutter speed also allows you to show movement in your photos or freezes moments. Slow shutter speed will show more movement, for example, a child running or playing. While a faster shutter speed will freeze the moment or action that you’re capturing.

Manual Mode

Manual mode is where you have to set all three adjustments manually, therefore, giving you complete control of the light and look of your photo.

Think of these three as a pulley system, all working together. When one is moved, one or both of the other settings must also adjust and compensate.


The photo on the left has a slow shutter speed, an open aperture, and low ISO. The slow shutter speed and open aperture help light enter. It also allows the camera to pick up the movement of the water.

In the photo on the right, we get more of an action shot of the water. This is because we have now changed the ISO to 1/2000 sec – a pretty fast shutter speed. With this fast shutter speed, we had to compensate for the loss of light from the fast shutter speed. So, we added light by using a higher ISO and a more open aperture. Even so, it wasn’t enough to get a correct exposure as the photo is a little dark.

The best way to get started in manual mode is to think about what kind of photo you want to make. Are you shooting still life? Is there enough light? Do you want to control your focus range? Is this a portrait? All of these things can help you to determine where to start.


For example, you’re taking photos of your kid’s soccer game in the early evening, and there is still a lot of light left, but it’s not harsh. You want to freeze the action of the game, and so you’d start by setting a fast shutter speed first.

If you’re taking a portrait of someone, then you’d start with the aperture in order to control your depth of field. Then you’d adjust the other two settings accordingly.

Image: Camera settings f/5.6, 1/100, IS0 400, 53mm.

Camera settings f/5.6, 1/100, IS0 400, 53mm.

For landscapes, you’d likely start with aperture and shutter speed. You may need a small aperture (eg f/11) to capture a wide plane of focus. Depending on whether there is water in your landscape, you may want to freeze the water or give it a silky look by slowing your shutter speed right down.

Knowing what you’re shooting and type of light will give you a starting point

Also, in manual mode, there is a built-in light meter. This meter looks like a tiny ruler either at the bottom of the live view or inside the viewfinder. It helps you determine if your photo is too bright (metering to the right), or too dark (metering to the left).

When the line is in the middle, or at zero, you’ve got what the camera considers a perfectly-exposed photo.


The ruler at the bottom of the live view, or through the viewfinder, can help you expose your photos correctly. To the right of the ruler your photo will be brighter, and to the left, it will be darker.

Aim to keep it in the middle as you practice in manual mode. Sett one of the adjustments and then move the other two to add or take away light accordingly until the meter is in the middle.

It’s all about practice and really getting to know what each setting does on its own before switching to full manual. This can feel overwhelming, so try using one of the other modes, like Tv/S or Av/A modes first. Doing so may give you a better understanding of the settings and more control over your photos.


Camera settings f/22, 30 seconds, ISO 200, 28mm.


Image: Camera settings f/10, 1/640, ISO 400, 50mm.

Camera settings f/10, 1/640, ISO 400, 50mm.


The technical side of photography can sometimes seem overwhelming and it seems like there is always something new to learn before feeling confident. Making sense of the exposure triangle will set your creativity free and give you full control of your camera.

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Jackie Lamas
Jackie Lamas

is a destination wedding and portrait photographer based on the beautiful beaches of Puerto Vallarta, Mexico. She earned her degree in photography from California State University, Fullerton. Jackie has over 10 years of experience as a professional photographer and teacher. When she’s not on the beach, you can find her writing on her blog and spending time with her baby and husband. See more of her work on Instagram.

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