Understanding The Exposure Triangle

When shooting on manual on a DSLR, it is important to understand how Aperture, Shutter Speed, and ISO work. Once you have a basic understanding of these concepts combined with a little bit of practice, you can know how to take properly exposed photos without much thought.

What is Aperture?

Aperture is defined as the opening in a lens that light passes through to enter the camera. Aperture size is expressed in f numbers- for example, a f/stop of 2.8 is a larger aperture (or hole) than a f/stop of 16 and lets more light in to the camera. Choosing a small or large aperture will determine the depth of the photograph you produce.

Wide Aperture

A large aperture is also known as a wide aperture. If you choose to use a wider aperture, you can produce photos with a shallow depth of field. Macro photography is a great example of shallow depth of field and wide aperture. The subject will appear in focus, and everything in the background will be blurred. Using wide aperture balanced with a faster shutter speed is a common technique used by portrait photographers. Here is an example of a photo produced by using wide aperture:

Photo by Paweł Czerwiński on Unsplash Canon EOS 77D Focal Length 105.0mm Aperture ƒ/2.8 Shutter Speed 1/320s ISO 100

Narrow Aperture

Utilizing narrow aperture will produce the opposite of wide aperture. When you use a narrower aperture, or a smaller f/stop, you can produce photos with a maximum depth of field and everything will be clear and in focus. Using narrow aperture and a slower shutter speed (while utilizing a tripod) is a common technique in landscape photography to produce photos that are in focus and clear everywhere, contrasting the blurring that occurs with a wider aperture. Here is a photo example to show the difference:

Photo by Ales Krivec on Unsplash NIKON D800 Focal Length 14.0mm Aperture ƒ/13.0 Shutter Speed 1/40s ISO 100

What is Shutter Speed?

Shutter speed is almost exactly what it sounds like- it is the amount of time that the shutter is open to allow light in on the camera’s sensor. Shutter speed and aperture can be balanced in an inverse relationship in order to produce properly exposed photos, but shutter speed on its own can be used to create its own artistic effect.

What is blurred motion and how do I use my camera to produce this kind of photo?

Blurred motion is the effect on a photograph you can see when a photo was taken with a longer, or slower, shutter speed. When the shutter is open for more time, more light is let in- but if objects are moving, such as water, you can use blurred motion to your advantage to create some visually stunning photographs. As you can see below, water will appear smooth when one uses blurred motion.

Photo by Robert Lukeman on Unsplash SONY ILCE-7RM2 Focal Length 18.0mm Aperture ƒ/18.0 Shutter Speed 1.6s ISO 100

What kind of effect will a faster shutter have?

A faster shutter speed will grab the light more quickly (and allows less light in, so it may require a larger aperture or higher ISO to get exposure correct). When one uses a faster shutter, the image will be frozen. Frozen motion images with a fast shutter can capture tension in a photo. (See the example below.)

Photo by Siim Lukka on Unsplash NIKON D7200 Focal Length 25.0mm Aperture ƒ/5.6 Shutter Speed 1/3200s ISO 400

What is ISO?

To put it simply, ISO is how sensitive the camera is to light. If the ISO is low, then the camera will be less sensitive. If the ISO is high, the camera will be more sensitive and will be able to capture more. The ISO will have a visual impact on the images when you take them. An ISO of 100 will have the smoothest appearance, and the highest ISO your camera settings can appear to be grainy. I personally prefer to shoot at an ISO of 100 if it is possible, however, sometimes it is necessary to shoot at a higher ISO in order to capture more light when you are in a dark setting. Below is an example of a photo that would require a high ISO.

Photo by Joacim Bohlander on Unsplash Canon EOS 70D Focal Length 10.0mm Aperture ƒ/3.5 Shutter Speed 30s ISO 1000

So how do Aperture, Shutter Speed, and ISO interact to create a properly-exposed photograph?

When shooting in manual, you need to be able to find the balance. Finding the balance and using the right settings will allow the correct amount of light in to create the correct exposure. If you want to have a large aperture, it is most likely your shutter speed will be fast assuming your ISO is constant. This is because the higher aperture will let in more light so you need to make sure too much is not coming in with a faster shutter. If you want to have a slow shutter speed, you will have to have a smaller aperture to balance the amount of light coming in from the shutter timing. The ISO enables you to capture the correct exposure in different settings, like a sunny day versus a dark night sky. Having a solid understanding of The Exposure Triangle will allow you to creatively express yourself and what you see through your chosen photographic techniques.