Exposure Triangle Explained
The exposure triangle is probably the primary fundamental to be mastered and understood and to ensure a solid basis for any photographer in any genre of photography.
Understanding the exposure triangle and its relationships between shutter speed, iso and aperture give the photographer the ultimate creative control over the photograph they are about to take when they press the shutter release button. These three components work together to create an actual exposure of a photograph. It is referred to as the exposure triangle because when you adjust one of these elements then another one or possibly both other elements MUST change to ensure you can capture the same exposure.
What is the meaning of each component and what does it do?
This component of the exposure triangle refers to the size of the hole (or opening) in your lens as you press the shutter button and take a picture. The aperture “controls the depth of field” (amount of sharpness) in your photograph. The larger the hole (or aperture), more light passes through that hole to hit the camera’s sensor with less DOF. Alternatively the smaller the hole (or aperture) less light passes through that hole to hit the camera’s sensor with more DOF. When discussing aperture it is typically expressed in “F” numbers, for example; F/2.8, F/4.0, F/5.6, F/8.0. F/11.0. F/16.0 (dependant on your lens capabilities).
Unfortunately, with modern lenses, F numbers are not marked on the lenses themselves but only visible when a lens is attached to a camera (DSLR) and then viewed through the viewfinder. Try it now, switch the camera over to manual (M) or aperture priority mode (AV) typically on a Canon camera, for example, and adjust your camera’s aperture dial (refer to your camera’s handbook for this) up or down and watch the F-number change in the camera’s viewfinder. You are now changing the aperture, a component of the exposure triangle.
Refer to the Aperture portion of the infographic for a more visual representation of what is described above.
Another component of the exposure triangle is ISO. In the film days, photographers use to refer to the sensitivity of the film to available. This sensitivity was based on an ASA numbering system. Therefore 100ASA film was less sensitive to light than say 400ASA film. However, there were drawbacks as higher ASA numbered film produced ‘grain’ in photographers finished photographs with the higher number producing more grain.
In today’s digital age, ASA has been replaced with the term ISO and grain has been replaced with the term noise. As we no longer use film (although some still do) our camera’s sensor captures the information once the lens aperture is opened, instead of the film. The sensitivity to light of the sensor can be adjusted by increasing (more sensitive to light) or decreasing (less sensitive to light) by adjusting the ISO. With a lower number, for example, 100 (ISO) you will have less sensitivity to light. With a higher number, for example, 1000 you will have more sensitivity to light.
It is important to remember, as with film, that higher numbers can cause grain (film days) or noise ( digital age) in your image. It is generally best to try and keep your ISO as low as you can to avoid digital noise in your images, however, sometimes noise as with grain can be used to creative effect.
Refer to the ISO portion of the infographic for a more visual representation of what is described above.
The final part of the exposure triangle is shutter speed. In short and simply put, a camera’s shutter speed controls how long your camera’s shutter stays open once you fully depress your shutter button on your camera. In other words, we can control how much light comes through to the camera’s sensor based on how long the shutter is open for. The longer the shutter is open, the more light will hit the sensor, equally, the converse is also true. Shutter speed also controls motion, so if you want to freeze motion you will need to have a faster shutter speed. If you wanted to get movement in your image (sometimes known as motion blur) you will have a slower shutter speed. Shutter speeds are expressed in a fraction of a second 1/15 (1/15th of a second), 1/30, 1/60, 1/125.
Refer to the Shutter Speed portion of the infographic for a more visual representation of what is described above.