THE EXPOSURE TRIANGLE – WHAT IS IT?

18th November 2021
Exposure Triangle

The Exposure Triangle – maybe you have heard of it but you aren’t sure what it is or how it relates to your photography? In this blog post, I’m going to help you understand exposure better and give examples of how you can use the exposure triangle to embed the theory behind it.

If you have a basic understanding of photography and exposure, you have probably heard about the 3 core elements that affect your exposure. Aperture, Shutter Speed & ISO. If you haven’t heard of these yet, don’t worry. I’m going to cover them briefly below. You can also learn more on my Online Beginners Photography Course which is going to be available very soon on the website!

Aperture

Aperture

There are two ways of controlling the light entering your camera. Firstly, with your aperture and secondly, your shutter speed. Aperture and shutter speed together determine the quantity of light that reaches the digital sensor.

Your Aperture is the opening in your lens which controls the amount of light passing through it. It can open to different sizes letting different amounts of light in. It also affects depth of field (the distance over which focus appears sharp within your image – the zone of sharpness).

Shutter Speed

Your Shutter speed controls the duration of light that enters your camera. Basically it’s how long you leave your shutter open for. The shutter (like shutters on a window) stays closed until you press the shutter button to allow light to enter.  It can open & close slowly or quickly. You shutter speed also reflects movement – it controls whether moving objects appear blurred or frozen in action.

ISO

ISO

The third thing that impacts on the brightness of your image is a setting called ISO – this function on your camera allows you to increase or decrease your camera sensor’s sensitivity to light. ISO controls how intensely the sensor reacts to the light. For any of you that ever used a film camera, you may remember how film had different speeds? It was a number on the film e.g 100, 200 etc. Well ISO correlates with film speeds, as digital sensors have replaced the film in cameras now. You can learn more about this on my Beginners Photography Workshop but that’s a general overview for now.

ISO also impacts on the amount of image noise/grain – this can compromise image quality and make your image look like it has little dots of sand on the photograph

The Exposure Triangle


You will be wondering how you make these 3 settings work together for you to achieve a perfectly exposed image? All 3 are interlinked – you have to remember that if you change one of these elements, it will have an impact on the others.  It’s a balancing act.

You can never really isolate just one of the elements alone but always need to have the others in the back of your mind. The Exposure Triangle is a common way of associating the three variables that determine the exposure of a photograph.

The Exposure Triangle

I know this can look a little daunting but I’ll explain.

The key is that when you allow more light in (via larger aperture or slower shutter speed) or increase the exposure (via ISO) for one of the 3 element (a yellow arrow), you need to reduce it for one or both of the other elements (the black arrows) in order to maintain the same exposure. That is, if you want the overall level of brightness in your image to stay the same.

For example, if you have ascertained the correct exposure to be as follows: – Aperture f8.0, Shutter Speed 1/250th & ISO 400. Then you decide you would like to use a larger aperture for creative purposes e.g f2.8. By increasing the amount of light coming in as you open up your aperture from f8.0 to f2.8, if you want to keep the overall exposure the same, you need to use a faster shutter speed and / or lower ISO. So your new settings could be Aperture f2.8, Shutter Speed 1/1000 and ISO 200.

Creatively your image will look different in terms of background blur but the overall brightness will remain the same. See the example below where the brightness is the same in each image but creatively very different.

The Exposure Triangle

The camera can do this for you automatically in Program, Aperture Priority or Shutter Priority modes. However, it’s something you’ll need to consider and work out for yourself when shooting in Manual mode.

Mastering the art of exposure is something that takes a practice. In many ways, it’s a juggling act. Even the most experienced photographers experiment and tweak their settings as they go. Keep in mind that changing each element not only impacts the exposure of the image but other aspects too.

The great thing about digital cameras is that they are ideal for experimenting when learning about exposure. They have built in light meters and you can take as many shots as you like at no cost. Not only do they allow you to shoot in Auto mode and Manual mode, their semi-automatic modes (aperture priority and shutter priority) allow you to make decisions about one or two elements of the triangle and let the camera handle the rest.

I hope you found this blog post useful. If you have any questions, feel free to contact me via the website or on Instagram. I’m happy to help you learn more about The Exposure Triangle or have a chat about your photography skills