In this beginner’s guide to the exposure triangle, you’ll find the exposure triangle in photography explained. Besides explaining what the exposure triangle is, I’ll show you how to use it to master exposure in photography.
Photography exposure is the process by which light, reflected from a subject, enters through the aperture in the lens and reaches the sensor for a specified period of time.
The sensitivity of the sensor determines the width of the lens aperture and the duration for which light can pass through.
The correct combination of shutter speed, aperture (F-stop), and sensor sensitivity (ISO) provides the proper photographic exposure (EV). The relationship among these three factors is known as the Exposure Triangle.
What is the exposure triangle in photography?
The Exposure Triangle is one of the best analogies to understand the photography basics that affect exposure: aperture, shutter speed, and ISO, and how they interact with each other to create photographic exposure.
Exposure is one of the most critical aspects of creating a good image, as it refers to the amount of light that reaches the camera’s sensor. In other words, it determines how bright or dark your photo is.
ISO: This is the numerical value assigned to the sensitivity level of the camera’s sensor.
Aperture: Controls the amount of light entering the camera.
Shutter Speed: Determines how long light passes through the lens.
Now that we’ve defined the three points of the Exposure Triangle, combining them in the right balance will give us a proper exposure.
The three elements of the Exposure Triangle need to be balanced to get a correctly exposed image. This means that changing one of the settings will impact the brightness, and you’ll need to correct it by adjusting one of the others too.
What are the exposure triangle camera setting?
Understanding the Exposure Triangle is essential to becoming a good photographer
The key to understanding how the exposure triangle works is to be familiar with the basic camera settings affecting each side of the triangle: aperture, shutter speed and ISO.
Not only do you need to understand what these three parameters are, but you also need to understand how they interact with each other.
What happens if you change the value of one of these three parameters?
What happens if you increase the aperture or lower the ISO?
For example, if you increase the ISO, you’ll need to compensate with a faster shutter speed or a smaller aperture to reduce the amount of light hitting the sensor. This keeps the exposure triangle balanced, resulting in a correct photographic exposure.
1 – The First Side of the Exposure Triangle: APERTURE
The aperture controls the amount of light entering the camera. This is managed through the diaphragm mechanism, which adjusts the opening size; when fully open, it allows the most light in, and when more closed, it restricts the light intake.
The maximum opening of a lens is known as its “maximum aperture” and is calculated by dividing the focal length of the lens by the diameter of the aperture. The resulting value is called the f-number or f-stop.
In practical terms, aperture is the lens opening, and the wider it is, the more light reaches the camera sensor, increasing exposure. Conversely, the narrower the aperture, the less light enters, making the image darker and reducing exposure.
For instance:
- f/1.8 is a large aperture, allowing a significant amount of light.
- f/20 is a small aperture, allowing minimal light.
You can also read our “What is Aperture ? Mastering Aperture in Photography” to learn more about this important factor of the exposure triangle.
2 – The Second Side of the Exposure Triangle: SHUTTER SPEED
Every camera has a shutter, which controls the flow of light. Shutter speed refers to the amount of time the camera’s shutter remains open, exposing the sensor to light. This setting directly impacts the overall exposure of the image.
The longer the shutter speed, the more light the camera sensor captures, resulting in a longer exposure. Conversely, the shorter the shutter speed, the less light hits the sensor, and the final image will have a lower exposure.
You can learn more about this side of the exposure triangle in our guide, “What is Shutter Speed? Mastering Shutter Speed in Photography”.
3 – The Third Side of the Exposure Triangle: ISO
This setting represents the camera’s sensitivity to light.
Digital cameras capture light through the lens aperture and the shutter speed. ISO is used to “artificially” brighten the image. However, increasing the ISO beyond a certain point can introduce digital noise, which reduces overall image quality. This effect must be considered when balancing the exposure triangle.
ISO is measured with values such as ISO100, ISO200, ISO400, ISO800, etc.
- Lower ISO values indicate less sensitivity to light, requiring more light for a proper exposure.
- Higher ISO values increase the sensor’s sensitivity, allowing for improved exposures in low-light conditions, but also increasing digital noise.
For more details, check out our guide, “What is ISO? Mastering ISO in Photography”, to deepen your understanding of ISO’s role in the exposure triangle.
How does the exposure triangle work ?
So how exactly does the Exposure Triangle work?
If you understand how the three elements of the Exposure Triangle in photography interact, you can achieve the perfect balance and get the right exposure in your photos.
To fully comprehend how the exposure triangle works, it’s essential to be clear on two fundamental concepts: what Exposure Stops are and how to Balance the Exposure Triangle in Photography.
Understanding exposure stops in photography
Exposure stops in the exposure triangle are essential for learning how to calculate the best settings for photographic exposure.
The theory indicates that a stop is the interval between one exposure value and the next. Increasing this interval by 1 stop means doubling the amount of light that reaches the camera sensor.
Thus, a photographic stop is a way to measure the amount of light hitting the sensor; with one stop, you can either double or halve the light.
For example, if I change the ISO by 1 stop up from 400 to 800, I double the amount of light. Conversely, if I reduce the shutter speed from 1/120 of a second to 1/60 of a second, I’m increasing by 1 photographic stop, again doubling the light that enters and hits the camera sensor. If I want to halve the amount of light, I need to decrease by one stop, bringing the ISO down from 800 to 400, for instance, and reducing the shutter speed from 2 seconds to 1 second.
As for the aperture, it’s not as simple to know what one stop is equivalent to, as it does not correspond to doubling or halving the F-stop number. However, we know that by narrowing the aperture (F4 rather than F2), less light will reach the sensor, and vice versa, by widening the aperture, more light will enter.
How to Balance the Exposure Triangle in Photography
This is your ultimate goal. In the exposure triangle of photography, it’s essential to find a balance among the three elements.
Any adjustment to one of these three elements (ISO, Aperture, Shutter Speed) will result in a variation in the other two. This phenomenon is known as “reciprocal alteration”.
If you allow more light in by using a larger aperture, you’ll need to reduce the shutter speed accordingly. Similarly, if you leave the shutter open for an extended period, you’ll need to decrease the amount of light that enters and hits the camera sensor, which can be done by lowering the ISO or decreasing the aperture.
The fundamental rule of the exposure triangle is to achieve balance. When the three sides of the triangle are in harmony, you obtain the correct exposure value (EV), which is typically close to zero.
Think of the area formed by the exposure triangle as a geometric figure; whenever you change the value of one side of the triangle, you must compensate by adjusting one or both of the other sides. If you lengthen one side, you must shorten the other two or one of the two, maintaining balance, as this is the ultimate goal of the exposure triangle in photography.
When we have an EV (exposure value) of zero, it means that the three elements—ISO, aperture, and shutter speed—are correctly balanced to achieve a balance in the exposure triangle.
If we want to close the aperture to gain more depth of field and we have, for example, 2 stops less of aperture, to maintain the same EV we need to increase the ISO by 2 stops or increase the shutter speed by 2 stops, or we can also increase both by just 1 stop each.
Some practical examples of how exactly the exposure triangle in photography works
First Case – Night Photography
We want to photograph the Milky Way, in low-light conditions. Our goal is to capture the night sky, and let’s assume that to achieve the correct exposure, we need to set the exposure triangle with the following settings: f/2.8, 20 seconds, ISO 5000.
Upon reviewing the file, we find that we have achieved a proper photographic exposure, but the stars appear as trails instead of points. To resolve this, we need to reduce the shutter speed from 20 seconds to 15 seconds.
Now, what adjustments must we make to maintain the same EV (exposure value)?
Reducing the exposure time by five seconds means that less light will enter, so we need to adjust one or both of the other two elements in the exposure triangle: ISO and Aperture (f-stop). Since we are already at maximum aperture (f/2.8), we cannot widen the diaphragm further to allow in more light. Therefore, we need to increase the camera sensor’s sensitivity by raising the ISO value, for example from ISO 5000 to ISO 6400 or even 8000.
Second Case – Subject in Motion
We want to photograph a fast-moving subject. We’ve set an exposure triangle that gives us a correct EV, but our subject appears blurry. Our current settings are: f/8, 1/60, ISO 1600.
This means we are working with a shutter speed that is too slow, so we need to increase it, which will allow less light to enter.
What do we need to do now to maintain exactly the same EV (exposure value) while getting a sharp image of our subject and freezing the motion?
We need to adjust one or two of the other parameters, ISO and aperture. Our new EXIF data to achieve the same EV while keeping the subject sharp could be: f/8, 1/120, ISO 3200, or f/5.6, 1/120, ISO 1600.
So, to compensate, we will need to either increase the aperture by one stop (from f/8 to f/5.6) or raise the ISO by one stop (from ISO 1600 to 3200) to rebalance the exposure triangle.
If we are capturing less light using a faster shutter speed, we must either use a wider aperture or increase the ISO to compensate and return to a balanced exposure triangle.
Third Case – Long Exposure
We are facing a seascape and I want to play with the motion of the waves. We have a correct EV based on the light in the scene, and our current EXIF data that make up the exposure triangle are: f/11, 1/60, ISO 100.
To extend the exposure time, we need an ND filter to reduce the light entering and hitting the sensor. We’ll use a 6-stop ND filter. This means we will have 6 stops less light reaching the sensor. We can adjust the shutter speed from 1/60 to 1 second while keeping the other two elements of the exposure triangle unchanged. Our new EXIF data will be: f/11, 1 second, ISO 1600.
It’s important to note that in this third case, we kept the other two elements of the exposure triangle unchanged because we reduced the light hitting the sensor by using a 6-stop ND filter.
Therefore, by decreasing the incoming light by 6 stops, increasing the shutter speed by 6 stops, and leaving the other two elements (aperture and ISO) unchanged, we achieve the same EV.
Fourth Case – Depth of Field
We are in front of a wide landscape with flowers nearby and mountains in the background. We position the camera close to the flowers, creating our photographic composition. We have a correct EV with the following EXIF data: f/8, 1/120, ISO 100.
We want to increase the depth of field to try to keep everything in focus, from the flowers to the distant mountains. Therefore, we need to work with a smaller aperture, for example, f/16. By closing the aperture to f/16, we allow 2 stops less light to enter, so we need to compensate for one of the other two values (or both) that make up the exposure triangle.
In this case, to balance the exposure triangle, it may be helpful to increase the ISO value rather than shoot with slower shutter speeds; this is because flowers often move in the wind. The new EXIF data will be: f/16, 1/120, ISO 400.
What is the most important setting in the exposure triangle ?
No element is more important than the others in the exposure triangle; there is no rule on which setting to adjust first or which side of the triangle to use for compensation.
As we have seen in the four practical cases, it all depends on what you want to photograph and what you want to create!
- If you want to photograph the night sky, you need to keep the stars still, and therefore you must follow a specific shutter speed while adjusting the other two elements.
- If you want to photograph a moving subject, you need to increase the shutter speed to freeze the motion of the subject, and thus work on the other two values: aperture and ISO.
- If you have a very close subject and want everything in focus, you must use a smaller aperture, and then compensate the exposure triangle with the other two values: shutter speed and ISO.
Photography tips and tricks – Practicing in the Field
When you are on location, experience helps you understand which of the three elements of the exposure triangle is best to adjust first to fit the scene:
- If you want to photograph a wide daytime landscape with flowers in the foreground and mountains in the background, you should first adjust the aperture (to decide the depth of field) and then compensate with the other two values: shutter speed and ISO.
- If you want to photograph the Milky Way, the aperture will always be the first value to adjust, and it should be as wide as possible to let in more light. Next, consider the second parameter, which is shutter speed, as you have a certain time limit before the stars begin to create trails. Then, adjust the ISO accordingly.
- If you want to photograph a bird, you will need a very fast shutter speed, making it the first element to adjust. Afterward, compensate the exposure triangle with the other two elements: aperture and ISO.
- You should know that in most cases, the first setting of the exposure triangle to adjust is either the aperture or the shutter speed. ISO is rarely the first setting you adjust; it is usually a setting used to balance the exposure triangle.
Useful tips to improve your photography
Things to Keep in Mind for Better Photography
There are a few things to keep in mind that will help you capture better photos and, in some cases, avoid having to discard images once you review them on your computer.
1. Using a Tripod: If your shutter speed is slower than 1/60 seconds, you should always use a tripod or compensate with the other two elements by increasing the ISO or using a wider aperture. Otherwise, the photo may turn out blurry and not sharp. In such cases, there’s little you can do in post-processing except discard the file.
2. Keep ISO Low: Try to keep the ISO as low as possible while compensating with the other two elements of the exposure triangle. This depends on what you are trying to achieve; for example, if you’re photographing a moving subject in low-light conditions, you will need to raise the ISO. Higher ISO settings result in more digital noise in the file. It’s important to know the limits of your sensor’s performance at high ISO levels and to use appropriate editing techniques to reduce digital noise.
3. Use Intermediate Apertures: Try to use a mid-range aperture, between f4 and f10, to achieve better file quality. In night photography, use lenses that perform well at their maximum aperture.
4. Check the Histogram: Always check the histogram on your camera’s display to verify whether your exposure value (EV) is correct. If the graph doesn’t touch either end, it means you’ve balanced your exposure triangle correctly. In cases where there’s a significant difference in light between shadows and highlights, resulting in high contrast, it may not be possible to have a correct histogram or EV in a single shot. In such scenarios, you will need to apply HDR techniques, taking multiple shots to recover both the highlights (underexposed EV) and the darker shadows (overexposed EV).
Learn “How to master photography histogram” to better understand your exposure settings.
Conclusion
I hope this guide on how the exposure triangle works will help you manage your camera’s exposure (EV) more effectively.
You can adjust the EXIF data (the three elements that make up the exposure triangle) as you wish to capture your scene in exactly the way you want. By changing one or two of these elements, your exposure value (EV) should remain stable, ideally staying close to zero.
If you learn to balance the exposure triangle correctly, you can vary one of the three elements to create the photo you desire, and the exposure value will remain unchanged.
To start, I recommend taking your camera, setting it to manual mode, and experimenting with the three elements: shutter speed, aperture, and ISO. Try to observe how adjusting each one affects the EV and the overall quality of the photo.
