Understanding the Exposure Triangle

For any budding photographer, understanding the exposure triangle is one of the first steps in their journey towards capturing perfect photos. The purpose of exposure triangle is to ensure the clicked images have the right exposure. In simple terms, exposure refers to how light or dark an image will appear. The perfect light setting is essential to avoid images getting underexposed (too dark) or overexposed (too bright.) Mastering exposure is considered as one of the basic photography techniques.

In a camera, exposure is determined by three key variables: aperture, ISO and shutter speed, also known as the ‘Exposure Triangle.’ Apart from light, exposure triangle also influences whether images are noisy/blurry or crisp and sharp. In this article, we explain the ‘Exposure Triangle’ in detail.

Aperture:

To put simply, aperture refers to opening of the lens, which allows light to travel into the camera. To draw parallels with humans, aperture is very much similar to pupil in the human eye; the pupil is a hole that allows light to enter the eye. The bigger the aperture, more light enters the sensor. So, if you double the opening or the aperture, the amount of light hitting the sensor is doubled.
Aperture is expressed in f-numbers, such as f/2.8, f/4, f/5.6 and so on. These numbers, also known as f-stops, are used for describing the openness/closeness of the aperture. Interestingly, when it comes to f-stops, a larger number means a smaller aperture or a smaller opening, whereas a smaller number refers to a larger aperture opening. So, an aperture setting of f/2.8 gives a larger opening, resulting in more light coming through as compared to an aperture of f/5.6. Whereas, an aperture of f/11.0 will give a much smaller opening, leading to much less light entering than say an aperture of f/4.

 


Image Credit: Todd Vorenkamp

 

ISO:

In a camera, sensitivity is controlled by an “image sensor” or sensor. The sensor plays a critical role of collecting light and transforming it into an image, thereby making it the most crucial and expensive part of any camera.
ISO determines how sensitive a camera is to available light. ISO numbers start from 100 and go up to 200, 400, 600 and so on. A higher ISO number of say 3200 or 6400 means the camera is more sensitive to light, whereas with a lower ISO number like 100 or 200 the camera is less sensitive to light. A higher ISO allows the camera to capture images even in low light without using flash. However, a drawback of higher ISO is the addition of visual noise to the image. It is advisable to stick to the base ISO (100-200) for optimum image quality.

Image Credit: Todd Porter and Diane Cu

 

Shutter Speed:

Shutter speed, which is measured in seconds, refers to the time the camera’s shutter is open. In other words, shutter speed is the time for which light is allowed into the sensor. Shutter speed is expressed as 1/15 (or 1/15th of a second), 1/30, 1/60 and so on.
The slower the shutter speed is, more light enters the camera, making it ideal for low light or night photography. For instance, a shutter speed of 1/8 will allow a lot of light inside the camera. If the shutter speed is high at say 1/4000, very less light will enter the camera. Note that slower shutter speeds can affect the sharpness of images, making them blurry.


Image Credit: Todd Vorenkamp

 

How to get the right exposure triangle?

In a nutshell, all these three variables relate to how much light (more or less) enters the camera. In order to get the optimum exposure, these three elements (aperture, ISO and shutter speed) need to work together. For any photograph, there are nth number of combinations of the exposure triangle. Also, there’s no single perfect combination for all these three variables, because light changes constantly. And that’s why for beginners, it can be challenging to create perfect harmony between the three.

 

Automatic mode:

Fortunately, almost all modern cameras have an in-built feature for balancing the exposure triangle. If you’re in automatic mode, your camera will automatically suggest an exposure depending on the brightness in the area.
In semi-automatic exposure mode, you get greater control to determine the exposure. So, for instance, if you’re shooting a scenery, you should be more concerned about getting the right aperture, because it controls how much of a scene is in focus. This can be done using aperture priority mode. Similarly, if you’re clicking an object in motion such as a car going by, you need to get the right shutter speed (using the shutter priority mode).

 

Manual mode:

In manual mode, ‘stops, which is the term for measuring exposure, comes into play. All the three variables – ISO, aperture, and shutter speed – can be measured in stops. For instance, an ISO of 200 is one stop more sensitive than ISO 100.
Without getting into too much technical jargon, stops help in balancing the light through the three different variables of exposure. If you’re taking light from one variable, you need to balance it by adding required number of ‘stops’ of light to the other side.
Let’s take an example of a bright sunny day where an ISO of 100, shutter speed of 1/125 and aperture of f/16 will give good exposure. Let’s say, the intensity of light has reduced and you want to change the ISO to 200. With this change, you are letting in one stop more light into the camera, thereby affecting the balance of the exposure triangle. To get the exposure triangle right back to optimum, you must reduce another variable, say shutter speed, by one stop to 1/250.

 

Final Thoughts:

In a nutshell, this explains the concept of the exposure triangle. If you’re a photography enthusiast, mastering the exposure triangle will give you better creative control over your photography and help you create better pictures. The key here is regular practice. Knowing which combination to use under which light setting and for which object can come only through trial and error. However, with the right amount of practice, one can easily master the exposure triangle.

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