Exposure Triangle: A Photography Beginner's Guide

The exposure triangle is a fundamental concept in photography. Understanding it is crucial to your improvement as a photographer, while mastering it will help you to achieve the correct exposure for all your images.

The three elements of the exposure triangle are aperture, shutter speed, and ISO. These three ‘sides’ of the triangle work together to control the amount of light that enters the camera and reaches the sensor. In other words, they determine the exposure of your image.

Exposure Triangle diagram

Exposure Triangle: Definition

For any given photo, there is only one truly correct level of exposure. But because the exposure triangle has three sides, there are hundreds of potential combinations of aperture, shutter speed and ISO that you can use to achieve that exposure.

If you have achieved the correct exposure for a given set of lighting conditions, and you then change one element of the triangle, you will need to adjust one or both of the other elements to maintain the correct exposure for your shot.

To explain this in more detail, let’s look at:

  • The Three Elements of the Exposure Triangle
  • Adjusting Exposure
  • Common Mistakes to Avoid
Diagram of different exposures

The Three Elements: Aperture, Shutter Speed, ISO

1. Aperture

Aperture refers to the opening in the lens that allows light to pass through. It is measured in f-stops, with each ‘stop’ referring to the halving or doubling of the amount of light passing through, relative to the next stop up or down in the scale.

The tricky part is that the lower the f-stop, the wider the aperture! But once you understand that, the concept is simple. A wider aperture (low f-stop) lets in more light, while a narrow aperture (high f-stop) lets in less.

2. Shutter speed

Shutter speed refers to the length of time your camera's shutter stays open when you take a photo. It is measured in seconds or fractions of a second.

A fast shutter speed gives a short exposure, making even moving objects appear frozen. A slow shutter speed will give a long exposure, often creating a blur effect.

Aperture and shutter speed diagram

3. ISO

ISO measures the camera's sensitivity to light. A low ISO setting (such as 100) means the camera is less sensitive to light, while a high ISO setting (such as 1600) means the camera is more sensitive to light.

Exposure Triangle: Adjustments

When you’re taking a photo with your camera in Manual Mode, you’ll need to adjust these three elements of the exposure triangle in order to achieve the correct exposure. How you do so will depend on the lighting conditions and the effect you’re looking for.

For example, in low light conditions, you may need to use a wider aperture (lower f-stop), slower shutter speed, or higher ISO to allow more light in. In brighter conditions, you may need to do the opposite: that is, use a narrower aperture, faster shutter speed, or lower ISO to reduce the amount of light.

Adjusting the exposure triangle can also help you achieve different effects, such as a shallow depth of field or motion blur.

Long exposure image of a stream running through a lush green forest

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Learning to shoot in manual mode will transform your images and give you the confidence to get out there and start taking truly great photos.

Common Exposure Mistakes to Avoid

When it comes to exposure and the exposure triangle, there are a few mistakes that novices make. These are easy enough to avoid if you keep the key principles of the triangle in mind.

One common mistake is overexposing your image. Overexposure means there is too much light in the image, making it look washed out. To avoid overexposure, you need to increase the shutter speed and/or decrease the aperture (that is, select a higher f-stop value).

Another common mistake is underexposing your image. Underexposure occurs when there is not enough light in the image. To avoid underexposure, you need to decrease the shutter speed and/or increase the aperture (by selecting a lower f-stop value).

A third common mistake is assuming that more sensitivity to light is always better, and therefore using higher ISOs. This can reduce the quality of your images, making them ‘noisy’ or ‘grainy’. To avoid this problem, always use the lowest ISO setting possible for the given lighting conditions.

Diagram showing different ISOs


Mastering the exposure triangle is essential for achieving well-exposed photos. Understanding how aperture, shutter speed, and ISO work together gives you the freedom to get as creative as you like – and to have as much fun as possible with your camera!

To learn more about exposure, download our free 90-page eBook, An Introduction to Photography.

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