The exposure triangle is one of the most important elements of photography. It also something that beginners can often find daunting. The good news is that the exposure triangle isn’t some sort of mathematical formula. It is simply an explanation of how the three main aspects that create any image are linked together.
Exposure triangle chart
The easiest way to understand the exposure triangle is to know the components that make it up. These are shutter speed, aperture and ISO. These three components of photography are what combine to allow a photo to be taken.
What is the significance of the triangle you may ask? Well, it is simply to show the relationship between these three settings. In other words, all of these settings are linked to one another and changing one has an impact on the others.
Exposure triangle explained
Before we look at how these setting impact one another, let’s briefly talk about each setting.
Shutter speed – Your shutter speed determines how quickly the aperture in your lens opens and closes. The faster it is the less light enters the camera.
That is why if you are photographing in low light conditions, you need a slower shutter speed. Because the shutter is open longer, the more light hits the sensor. Which is what you will need in dark conditions.
A fast shutter speed will also help to freeze any movement to avoid motion blur. For example, if you are photographing a cheetah running you will need a fast shutter speed to freeze the action.
Aperture – While the shutter speed controls the speed of aperture, aperture controls how much it opens. This is shown by an f/number (i.e. f/4.5, f/8 etc).
The higher the f/number the smaller the opening of the aperture. So, for example, f/18 is a very small aperture whereas f/2.8 is a wide aperture.
The size of the aperture controls something called depth of field. This is basically how much of the composition in the photo will be sharp from the foreground to the background. If you have a wide aperture (low f/number) you will have a much shallower depth of field. So for example if you took a photo focusing of someone’s eyes with a wide aperture, the background will be blurred.
But for example, in a landscape scene where you need the entire focal plane in focus, you need to use a narrower aperture (higher f/number).
ISO – The third component of the exposure triangle is ISO. Back in the days of film, the ISO determined the sensitivity of the film to light. In digital photography, all that has happened is that film has been replaced by a digital sensor. So the higher your ISO is the more sensitive the camera’s sensor becomes to light.
This is useful in situations where you are shooting handheld and need to have a faster shutter speed or smaller aperture. Unfortunately, raising the ISO setting too high will have a negative impact on the quality of your image. At high ISOs, you will see noise which will make the photo appear soft and less sharp.
Exposure triangle – aperture, shutter speed and ISO
Earlier I mentioned that these three components all have an impact on one another. Learning this relationship between them will become invaluable in determining what camera settings you should use in each scenario.
Your starting point when deciding what setting you should use in any given scenario should be either the shutter speed or aperture. This is because your ISO should always be as low as possible.
A good starting point to determining your setting is if you are going to be using a tripod or shooting handheld. If you are using a tripod than your shutter speed can be as slow as you want. This allows you to select your depth of field first and then select the shutter speed accordingly.
But if on the other hand you are going to be shooting handheld, that means that your shutter speeds becomes vital. If it is too slow, your image will be blurred. Everyone will vary in how steady they can hold a camera and image stabilization in lenses does help. But no one will be able to hold a camera steady even for 1 second.
If you are shooting handheld, a good way to start is by determining your shutter speed. Then select your aperture (how much of your image needs to be in focus). Finally, raise your ISO to the point where you can achieve a good exposure. If you are going to select your aperture first when shooting handheld, make sure that your shutter speed isn’t too slow when you take the shot.
A few examples to help you
Example 1 – For this example, you are going to be photographing a landscape scene using a tripod. Straightaway you know that shutter speed shouldn’t be a problem (unless it is really windy).
Typically, for a landscape shot you need as much of the scene to be in focus as possible. So you need to select a narrow aperture to get a great depth of field. A starting point should be around f/8 and upward. Let’s say you select f/16.
Because your aperture is so small, the amount of light entering the camera will be very small. So your aperture will have to remain open for longer. But because your camera is on a tripod, that isn’t an issue. So there will be no need to raise your ISO at all and you can keep it as low as possible.
Example 2 – This time, you are taking a portrait of someone outdoors. There is good light but you are shooting handheld. So immediately you know that your shutter speed can’t be too slow.
As it’s a portrait you also want to keep the depth of field shallow so that the focus will be on the person’s face. You decide to select 1/100th sec shutter speed and f/3.2 and as there is good light ISO 100. But you realise that this will mean your image will be too bright.
You can either select a smaller aperture or a faster shutter speed. The latter will allow you to keep your aperture at the desired amount.
Example 3 – In this scenario, you are photographing a market vendor in a covered market. You are shooting handheld so you again set your shutter speed at 1/100th sec.
But this time you want a slightly greater depth of field as you want to capture some of the surroundings of your subject. So this time you select f/5.6. But because of the low light, your image is too dark. So you increase the ISO and select ISO 200 instead and now have a much better exposure.
As you can see, in all of these scenarios, the different components of the exposure triangle can be changed to help you be able to take the photo you want.
With practice and experience, the components of the exposure triangle and their relationships to one another will become second nature. There are plenty of cheat sheets out there, but I would encourage you to try and learn without them. Because if you can, you will subconsciously be able to select the relevant setting and tweak others not just to take a photo, but for creativity as well.
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Kav Dadfar is a writer and travel photographer who has written over 400 articles on photography. He is also a judge on the Wanderlust Travel Photography of the Year competition and a speaker at camera clubs and events. He has years of experience shooting assignments with his images having been used by some of the biggest brands in the world.
This exposure triangle photography article and photos is subject to copyright. Words and photos by Kav Dadfar (That Wild Idea). Copying or reposting of photos or article elsewhere is strictly forbidden.