Exploring the Exposure Triangle in Landscape Photography

by Dec 23, 2020Photography Tutorials

Robin Whalley Landscape Photographer

Exploring the Exposure Triangle in Landscape Photography

When starting to landscape photography, one of the first things you should learn about is controlling your camera. But this mean learning to use all those fancy features manufacturers stuff into cameras so they can charge lots of money. Instead, you need to learn about the fundamentals of photography and, something we call the Exposure Triangle.

In landscape photography the Exposure Triangle is fundamental to shooting high quality photos. Despite this, it’s not uncommon to find even experienced photographers (people who’ve has been taking photographs for more than a couple of years) using their camera in the automatic mode. What seems to happen is that when someone purchases their first camera, they start by using the auto option. And because the auto mode is easy and produces relatively good images, they continue to use it. Unfortunately, they never gain the creative benefits the Exposure Triangle can bring to their work.

Please don’t be one of those photographers forever stuck in the auto mode. Learn to control the exposure triangle and inject some creativity into your photography.

What is the Photography Exposure Triangle?

The photography exposure triangle explains the relationship between three camera controls used to obtain a “correct exposure”. These are the Shutter Speed, Aperture, and ISO setting. We will cover each of this in a moment but first we need to look at the term “correct exposure”.

Diagram of the exposure triangle

A “correct exposure” is the term used to describe what the camera thinks is a well exposed image that’s neither too light nor too dark. The camera works out the exposure for a scene by determining the average brightness across certain areas in the frame. If the camera is in the auto mode it then adjusts the controls of the exposure triangle so that the average brightness of the scene comes to a midtone grey value. If it achieves this, the exposure for the scene is correct.

If you are wondering why I keep placing the words “correct exposure” in brackets, it’s because it may not be the best exposure. If you photograph in the blue hour as I often like to, you will know that the “correct exposure” will not make the image look good. Typically, you would need to shoot an image that the camera determines would be underexposed to bring out the beauty.

Example of blue hour landscape photography

When shooting in the blue hour you often can’t rely on the camera’s calculated exposure.

To understand how we can take control of the camera exposure, let’s talk about the three components of the exposure triangle in greater detail.

The Aperture

The aperture is an adjustable hole in the lens which allows light to pass through to the sensor. We measure the size of this hole in f-stops. The smaller the f-stop number the larger the hole and the more light it allows through. For example, a setting of f/2.8 would allow more light to pass than a setting of f/8. The larger the f number the smaller the aperture and less light it allows through.

If you think about this, when less light is reaching the camera sensor, we create a darker exposure unless we change some of the other settings in the Exposure Triangle. If we don’t change the other settings, we will produce an underexposed photo. This is what the Exposure Triangle is all about and how you can improve your photography.

But let’s say we wanted to maintain the “correct exposure”. In this example, if we reduce the light reaching the sensor, to maintain a good exposure, we could increase the time the camera shutter remains open. This is where the shutter speed comes into the exposure equation.

Shutter Speed

The shutter speed measures the duration the camera shutter is open when you take a photo. The shorter the duration (or faster the shutter speed) the less light reaches the camera sensor. If we don’t adjust the other controls in the exposure triangle, a shorter shutter speed reduces the exposure creating an underexposed photo.

Therefore, changing the aperture means we will need to change the shutter speed to keep the exposure correct. Or to think of it another way, allow the correct amount of light to reach the camera sensor. That is unless we change the third control in the exposure triangle, the ISO.

ISO

The ISO setting is the third element of the exposure triangle and controls how sensitive the camera sensor is to light. If we make the sensor more sensitive to light, we don’t need as much light to produce a correctly exposed image. This could allow us to use a faster shutter speed and/or a smaller aperture to achieve the same exposure

It’s these three controls of the exposure triangle, the aperture, shutter speed and ISO, that allow us to produce the correctly exposed image. And because there are three of these, we need to change two or three of them to maintain an exposure. What’s not possible is changing only one of the three to produce the same exposure.

The Hidden Objective of your Camera

We have already said that when you have your camera set to photograph in the auto mode, the camera takes control of these three settings. I’m sure that you’ve already realised that many different combinations of exposure triangle settings can all create the same exposure. If this is the case, then how does the camera decide which to pick?

To help the camera determine which exposure settings to use, it has a secondary objective other than just achieving a good exposure. It also wants to minimise the chance of camera shake ruining the picture. Because of this the camera will choose settings that should allow you to shoot handheld and produce an image without shake. It does this by trying to produce a fast shutter speed. Whilst you might think this is helpful, it could have unintended consequences.

Unintended Consequences

You already know that there are three camera controls in the Exposure Triangle and that you can alter these to control the exposure. If you want to achieve a fast shutter speed you would need to adjust the aperture to allow more light to reach the camera sensor. Alternatively, or even as well, you increase the ISO to make the sensor more sensitive to the light.

Unfortunately, there are limits to the level of adjustment you can make to these settings as well as there being unintended consequences.

Aperture Consequences

Taking the aperture as an example, this doesn’t only control the amount of light able to pass through the lens. It also controls something called the depth of field in the image. The depth of field is the region of the photo either side of the focus point that appears to be in focus. Outside of the depth of field, the image starts to appear blurred. And the further you move away from the point of focus, the greater this blurring becomes.

This depth of field effect is a creative control the photographer can use to produce more pleasing photography. A good example of this is when you shoot a portrait of someone. Typically, you might want to focus on their face but then throw the background out of focus to remove any distractions. When you use your camera in auto mode you are throwing away this creative control. Yes, the camera may determine this is a portrait and the background needs to be out of focus, but then again it might not.

To create a shallow depth of field where there is only a small area in sharp focus, you need to use a wide aperture. But looking at the exposure triangle this means we need to change the shutter speed and or ISO setting to maintain a good exposure.

Image showing full depth of field

When shooting images like this with a wide-angle lens, achieving a good depth of field is the most important priority.

At the other extreme, if we want to shoot photography with a large depth of field as we often do in landscapes, we need to use a small aperture. Again, this means we need to change the shutter speed and or ISO setting to maintain a good aperture.

Shutter Speed Consequences

When it comes to the shutter speed, changing this can change the feeling or atmosphere in a photograph. If you use a fast shutter speed you freeze any movement in the frame. This may be important if you are photographing fast moving sports.

Here you can see movement in the foreground heather to create the feeling of wind emphasising the stormy conditions.

Here you can see movement in the foreground heather to create the feeling of wind emphasising the stormy conditions.

In landscape photography we often want to do the opposite by capturing a feeling of movement so that moving objects become blurred. Sometimes this may mean blurring moving objects so that they vanish or perhaps just capturing enough movement to show there is a breeze blowing. Both cases require we use a slow shutter speed but to different degrees. Having this level of control over the shutter speed requires an understanding of the exposure triangle and how we can further manipulate it with photographic accessories.

ISO Consequences

When we change the ISO setting of the camera to change how sensitive the sensor is to light, we can introduce image noise. Image noise is something to be avoid in landscape photography as it makes it can damage fine details in the scene. Instead of appearing sharp, fine detail like rock texture and grass can be blurred by sensor noise. And whilst you can correct noise to some degree using noise reduction, this can also damage fine details in the image.

When shooting landscape photography, it’s important to shoot at a low ISO setting most of the time, preferably using the base ISO for the camera. This produces low noise levels in the photograph whilst maximising the dynamic range the camera can capture.

The Exposure Triangle and Compromise

You should now understand the three controls of the exposure triangle and the unintended consequences adjusting these can have. Exposure control in landscape photography is all about compromise. On the one hand we have the creative aspects of the image whilst on the other we have technical concerns of capturing a good exposure.

If you want to maximise image quality, you will need to photograph using the camera base ISO. This ensures a low noise image that captures a good dynamic range of tones. At the same time, you may want to capture a full depth of field so will probably need to use a small aperture setting. By controlling both settings, the exposure triangle tells us that we need to use a longer shutter speed. But it’s not quite as simple as just changing the shutter speed. It’s possible this longer shutter speed may be too slow for you to hand hold the camera.

When you face a situation like this, it’s important to realise you will need to compromise. Start by determining which aspect of the exposure triangle is the most important to control and which you can sacrifice. For example, you may feel that a fast shutter speed is most important and that your camera can shoot acceptable quality images as high as ISO3200. In this situation, you could prioritise shutter speed over image noise and use a higher ISO.

Whilst the exposure triangle helps us understand how we can adjust our camera, the camera and lens place other constraints on the photographer. This is where you may need to consider using photographic accessories to overcome the limitations.

Using Accessories to Overcome Limitations

Let’s return to our example of using a low ISO setting and small aperture to photograph a landscape scene. This may require a slow shutter speed that we can’t handhold without the image showing camera shake. In a situation like this, we need to use a camera support like a tripod. The shutter speed then becomes much less important as the tripod will hold the camera steady almost indefinitely.

Now take the opposite situation where we are photographing a waterfall in strong light. The most important creative aspect of photographing this might be capturing movement in the water. This requires us to use a slow shutter speed and the exposure triangle tells us we need adjust the aperture and/or ISO to do this.

Long exposure to capture water movement

Here filters were used to extend the exposure, capturing the movement in the water.

In a situation like this we may decide to slow the camera shutter speed to 0.5 seconds to blur the waterfall to the correct degree. Unfortunately, neither the aperture nor ISO setting offer enough adjustment to achieve this. We may already be using the lowest ISO setting and a small aperture. When this happens, we need to turn to neutral density filters for help.

By adding a neutral density filter to the front of the camera lens we can reduce the amount of light reaching the sensor. This in turn slows the shutter speed without needing to adjust the ISO and Aperture further.

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Creative Camera Control

Whilst we have talked a lot in this article about controlling the different aspects of the exposure triangle, we haven’t said how. All that’s been stressed is that you shouldn’t use the auto mode. So how do you control the aperture, shutter speed and ISO?

Control of the ISO is relatively easy with most cameras. Most cameras have a dial or a menu where you can select a set ISO value. Just be sure to avoid the “Auto ISO” setting.

When it comes to controlling the aperture and or shutter speed, you will need to use something called the “camera creative controls”. These aren’t special effects but settings where you can prioritise controlling different aspects of the exposure triangle. You can find out more in my Creative Camera Control article.

Exposure Triangle Summary

In this article we’ve explored the exposure triangle, applying it to some common landscape photography situations. We know that by adjusting the aperture, shutter speed and ISO settings we can control the exposure. We must not leave these decisions to the camera (by using the auto setting) because we give up important creative controls.

We know that there are limitations and consequences to adjusting each of the controls of the exposure triangle. These are important in landscape photography so its important to decide for each image which of the creative controls you want to use. Based on this you can make decisions about how to adjust the other controls in the exposure triangle.

At times, we will encounter limitations and constraints in what we are trying to achieve. When this happens, we should use accessories like the tripod and filters to extend our control of the exposure triangle.

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