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How Understanding the Exposure Triangle Will Help You Get Better Pictures

July 14, 2015

Laura Morita

You got your new fancy Canon DSLR camera. You’re already excited about how much better your photos are just in green auto mode! While you love some of the images you get, you are at the point where you are starting to get frustrated. You want more consistency. You get some images that are amazing, but others that fall flat and you have no idea why. If you’re nodding like an enthusiastic bobble head doll and wondering how on earth I was IN YOUR HEAD, it’s because that’s exactly how I felt seven years ago. If you’re ready to step away from green auto mode (eek! the horror!) and move onto actually controlling your camera so you get the images you want, you’re in the right place! In this series of articles, I hope to help you understand both your camera and light better, so you can start getting pictures that you’ve always imagined.

A year after receiving my Canon Rebel, I wanted better control over my camera. There were so many dials and buttons and all I had ever used was the green “Auto” setting. A big step in getting that control over my camera was beginning to shoot in the Manual exposure mode. When I was ready to take that step, the first thing I learned was something called the Exposure Triangle and, while this might conjure up mysteries like the Bermuda Triangle, I promise you it’s not at all baffling! So let’s get started!

Exposure Triangle

Exposure is basically how bright or dark your image is and is controlled by three components: aperture, shutter speed, and ISO. Changing just one of those three components will affect the brightness or darkness of your image. They are not separate entities. If I have an exposure that I’m happy with (it’s not too bright or too dark), and I change one of the three corners of the exposure triangle, I will have to change another component of the triangle in order to again achieve my ideal exposure. Understanding what each of the three corners of the exposure triangle does is your first step in really starting to take control over your imagery!

Aperture, shutter speed, and ISO are all “Light Superheroes.” They share the responsibility of allowing more or less light into your camera, but beyond that, each of them also has a second special talent, which will be discussed below.

Aperture

As a portrait photographer, I consider aperture to be the most important component of the exposure triangle. Aperture is the size of the adjustable opening inside your lens and is measured in f-stops. You may hear people refer to it as a lens opening, f-stop, diaphragm, or iris. All these terms mean the same thing — the size of the lens’s aperture.

If the opening is big (large aperture), it lets in more light. If it’s small (small aperture), it lets in less light. Now, just to keep things interesting and completely counter-intuitive, a large aperture is indicated by a low f-stop number (like f/2.0) and a small aperture is indicated by a high f-stop number (like f/22). So if you hear a photographer talking about "opening up" or "stopping down," they are talking about decreasing or increasing the f-stop number, respectively.

Thanks aperture/f-stop naming people... we so appreciate the confusion. Sheesh. Take heart, however: the numbers mean the same thing across the photographic landscape. So once you learn this, the same information applies with all DSLR cameras and lenses.

Aperture’s special talent is controlling depth of field. Depth of field is how much of your photo will be in focus and how much will be blurry. If you’re in love with that blurry background look in portraits — where the subject is sharp, but the background is just a blur — that’s known as a shallow depth of field and is achieved in part by using a large aperture (a low f-stop number). An image where the background’s in sharper focus has a deeper depth of field and corresponds to a small aperture (a higher f-stop number).

Put simply: if you want a blurry background, you want a large aperture (low f-stop). Your widest, or largest, aperture is determined by your lens, not your camera, so the larger the aperture on your lens goes, the easier it will be to achieve this blurred look. My first lens, besides my kit lens, was the EF 50mm f/1.8 lens. It’s an affordable lens and, dang, it takes your portraits to another level. I didn’t really understand the impact of depth of field, until I had the "nifty fifty" lens.

When I’m making a decision on what aperture I want, I have to consider my subject(s) and what I’m trying to achieve. If I’m shooting a portrait of a single person, who isn’t moving too much, and I want the focus to be all about my subject, I can probably choose a large aperture, like f/1.8. This will give me a shallow depth of field, allowing my subject to be clear and sharp while the background fades away into blurry wonderland. If I’m shooting a group of people, while it’s possible to still shoot at f/1.8, that will require careful positioning of your subjects so that they are all in the same plane of sharp focus. And because that plane of focus at f/1.8 isn’t that deep, they’ll need to all be in a straight line perpendicular to your camera. Generally, groups require a smaller lens aperture. A good rule of thumb: Make your f-stop equal or greater to the number of people in the group. If you’re shooting four people, choose at least f/4 . Shooting eight? Try f/8. But again, keep in mind that a wider lens aperture is possible, as long as your subjects are within that plane of sharp focus.

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Shutter speed

Shutter speed is how long the shutter is open. During the time the shutter is open, light is coming into your camera’s sensor and your image is being recorded. Shutter speed’s special power is either freezing or showing motion. If you want to freeze motion, you want a fast shutter speed — that is, the shutter is only open for a very brief fraction of a second. A fast shutter speed might be something like 1/500th of a second, or 1/1000th of a second. If you want to show some motion, you can have a longer or “slower” shutter speed. This could be something like 1/60th of a second, 1/15th of a second, and so on.

Shutter speed is measured in seconds or fractions of seconds. A shutter speed of 1/500 of a second is designated as 500, and you’ll see this in your viewfinder. Full seconds are designated on your camera with a quotation mark — for instance, an 8 second exposure is shown in your camera as 8".

Most children’s photographers aren’t using a tripod. I can’t imagine trying to chase after a kid while having my camera on a tripod! So, not only do we need to account for the speed of our moving targets, but we have to account for the fact that we are hand holding our cameras — any motion that WE make while holding the camera will also be recorded on our image. If my shutter speed is too slow for my moving camera, I will record that motion and end up with a blurry image. A good rule of thumb when hand holding your camera is to have your shutter speed denominator (the bottom number) equal to or higher than the focal length of your lens. The focal length of your lens is designated as “mm.” So, if you have a 50mm lens, you’ll want your shutter speed at least at 1/50. If you have a 100mm lens, you’ll want it at least at 1/100.

But I’m going to be honest... I am a shaky shooter. “Shaky McShakerson” is my actual name. Seriously. I am hyper when I shoot because I’m interacting with my subjects trying to get fun, happy expressions. So, there is no way on earth that I would be able to hold my camera with an EF 50mm lens at 1/50. and capture anything that is remotely in focus. Unless it’s a sleeping child, then I’ll take a moment to go all zen. So, while it’s a nice guideline, there are other things to consider. The more you shoot, the more you’ll learn what shutter speeds you need to get consistently sharp pictures when you are hand holding and you’ll find that this shutter speed will differ depending on what lens you are using.

If you have a lens that has image stabilization, turn it on. It’s a switch on the side of the lens that says “STABILIZER,” and it will help minimize camera shake so that you can shoot at a slower shutter speed while hand holding and still get a sharp image!

A big thing to consider when determining your settings is the movement of your subject. If you have a fast little bugger you’re trying to photograph, you’ll want a faster shutter speed to freeze motion. Typically, for me, if I’m photographing moving kids, the slowest I’ll set my shutter speed is 1/250. If they are running around, I try to increase that to 1/500, and if they are running and jumping like crazy, I’ll increase it even more to 1/800 or 1/1000. One reason to love digital cameras is that you can shoot a LOT and throw out the ones that don’t work.

When I’m trying to capture a lot of motion, I have my camera’s Drive mode set to shoot “high speed continuous.” This allows me to hold my shutter button down one time and capture a sequence of images. Some cameras, like the EOS 5D Mark III, can shoot up to six frames per second this way. I can then go through them later, then determine my best and sharpest images and delete the others.

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ISO

The third corner of the exposure triangle is ISO. ISO is the measure of light sensitivity of your sensor. Do you remember back in the day when you used film? If it was a bright, sunny day, you used a film rated for 100 (a low ISO.) If it was darker or you were shooting inside, maybe you’d use 800 film (a higher ISO.) Those numbers are still used today with digital cameras. The lower the ISO, the less sensitive your sensor is to light, so you need a lot of light coming into your sensor. The higher the ISO, the more sensitive your sensor is to light, so you don’t need as much light coming into your sensor. There is a tradeoff, however. High ISOs, while more sensitive to light, introduce digital noise (or grain) into your image. That noise means your image will not appear as clear and crisp, especially if it’s viewed at a large size. ISO’s special power is allowing more light onto your sensor with higher ISOs, but it’s kind of an evil power because this also introduces noise into an image, which isn’t usually desired.

So, that’s it. The three corners of the exposure triangle explained: lens aperture, shutter speed, and ISO. As I said before, those three corners work together. Changing one corner affects your exposure. With every image you take, you need to decide what do you want to capture and what will your settings need to look like to get that look. Here’s an example.

Putting it All Together

You’re taking pictures of your friend’s family. The sun is going to set in about an hour and a half. You place them in an area where they are shaded, but it is still bright. In choosing where to have them sit, you take into account that you want them to be the main subjects so you make sure you don’t have any trees or bushes directly behind them. In other words, you pull them away from the background. Because it’s still pretty bright, you set your ISO to 200. The kids are being pretty cooperative and you’re able to position them so that all of their heads are pretty close to each other. This is key because you want to be able to use a large aperture so that the trees in the background don’t start looking busy and distract from the family. Because they aren’t moving in and out of the plane of sharp focus (they aren’t leaning forward or backward in relation to you), you choose f/4 as your aperture. (Remember the guideline of making your aperture equal to the number of people?) With your camera in Manual exposure mode, you check your meter (we’ll talk more about your meter soon!) and set your shutter speed so that your meter is set to zero, indicating a "proper" exposure. You see that this makes your shutter speed 1/160.

Well, a couple things will start running through your head:

  1. You’re a shaky shooter, and you know that you can’t handhold the camera at 1/160 and get a sharp image.
  2. The kids, while being pretty cooperative, are, after all, still kids, and are moving their hands around a bit. With a shutter speed of 1/160, their hands will likely be blurred.

So, you realize you’ll need to increase your shutter speed. No problem! You decide to increase it to 1/320. You know that you can hand hold your camera with this lens (the EF 85mm f/1.8) at 1/320 and get a sharp image and you think that will be fast enough to freeze the moderate motion that might be happening in the kids’ hands. Are you ready to take your shot? Not quite... Because you increased your shutter speed, which means less light. Your image will be underexposed (too dark) if you don’t look at the other two corners of the exposure triangle and make a change...

So what do you change? You need more light... You can make your aperture larger, thus allowing in more light, but this will make your depth of field shallower and you don’t think you can get everyone in focus if you stop down any further. So, you need to change your ISO. You need more light, so you need to increase your ISO. By increasing your ISO from 200 to 400, you allow in more light and now get a good exposure! You focus on one of the subject’s eyes that’s closest to you and, boom, you get an image where everyone is sharp and there’s no motion blur.

After you shoot the family, you want to get some individual portraits of the kids. Now that there’s only one subject, the f/4 aperture isn’t necessary. You choose to open up your aperture more and choose f/2.2, thus allowing for a shallower depth of field. While your lens does go to f/1.8, this is a really narrow depth of field and even if the kiddo turns their head slightly, you could end up with one eye sharp and one eye out of focus. Also, by not shooting completely “wide open” you increase your chances of having more images that are in focus. You place your subject in an area where, again, you pull them away from the background. You want the focus on your subject, not the shrubbery, so by placing them further away from the background will ensure that your background will be out of your shallow depth of field and, thus, nice and blurry. You have your ISO at 400 because the sun has continued to set and there is less light to work with, but that’s fine because you opened up your aperture and have plenty of light to work with. You set your shutter speed to 1/400, fast enough for controlling camera shake and for your seated subject’s movement, and you get the perfect exposure. Yay!

For me, this is a fairly typical scenario. First, I choose my aperture based on the effect I want and then, because I normally want my shutter speed at at least 1/250s when I’m shooting children, I make sure that my ISO is high enough to allow this choice. While a higher ISO will mean more grain, I will always make the choice to have my shutter speed high enough to control camera shake and freeze motion because I would rather have a little bit of grain than an out of focus, blurry image. I also usually shoot group shots first because everyone is a little bit more cooperative when we first start and also because I know I’ll need a smaller aperture to get everyone in focus, which means I’ll be letting in less light into my sensor. 

I typically shoot during the “golden hour,” an hour or so before sunset, so I know as the session progresses, it will be getting darker. By saving my individual portraits for the end, where it’s fine for me to have a larger aperture, I ensure that I won’t have to bump up my ISO too much and get really noisy images. 

Some photographers will feel that an automatic exposure mode will make some (or even all) of these choices for me, simplifying things. But by working in the Manual exposure mode, once I learned how to work within the Exposure Triangle, I had full control over my camera and my pictures.

It’s not that confusing now, is it? Now go out and practice! 

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Laura Morita
Laura Morita

Laura, a professional child and family photographer, has a love of photographing children and families that is contagious and hopes to pass on her knowledge to you so that you can take better pictures of your loved ones.

Laura Morita

Laura, a professional child and family photographer, has a love of photographing children and families that is contagious. She also has a love for teaching and enjoys when she sees the lightbulb come on when her students understand a concept. She teaches online editing workshops, presented on child photography and editing at Click Away 2014, and gave several presentations on child photography at Canon's Live Learning San Francisco center in 2014. Her goal is to make the process of photography fun, while still teaching the technical aspects to help your photography go from “blah” to “ta-da!”

Laura began honing her eye for photography long before she knew how to use a camera. She spent years learning from her father, a talented photographer and a natural teacher, who gave slideshows of his slide film when she was younger. Those early lessons on composition, light, and visual impact still influence how she shoots today. He remains her biggest fan and best critic to this day. 

Laura first started shooting with a Canon EOS Rebel when her second child was one year old. For the first year, she kept the dial on “Auto” until she was truly ready to learn how to take control over her camera and have creative freedom. Now, eight years later, she is taking beautifully posed and candid portraits, which are colorful, fun, full of life and, most of all, capture the essence of her subjects. She hopes to pass on her knowledge to you so that you can take better pictures of your loved ones.

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