The Exposure Triangle

The Exposure Triangle


The first thing to understand when learning to shoot manually is something called “The Exposure Triangle”. Exposure is a technical term to describe what settings made up your image.

Its called the Exposure Triangle because, as you can imagine,  your Exposure is made up of three different camera settings. They are ISO, Aperture  and Shutter Speed.


Before digital cameras came along, Film was used to capture your image. When you pressed the shutter, your image passes as light through your camera and it hit the film. ISO was the term used to describe how sensitive the film was to the light that hit it. In the digital age there is no film. Light passes through your camera and hits the cameras sensor. Their is a school of thought that says ISO is how sensitive your cameras sensor is – this is however untrue. The sensor can deal with all ranges of light – it is not sensitive to it. In its simplest form, the ISO setting in modern day DSLRS is just a measurement of how much light is added to the image by the camera. ISO starts at a level of 100 (although some cameras can go down to ISO 50) at a base level and can increase to a very high number – the higher the ISO the more ‘grain’ is added to an image. We will talk more about ISO in a separate blog post

Shutter Speed

The easiest way to explain what a camera’s shutter function is, is to imagine it as ‘blinking in reverse.’ When we blink, our eyelids come down and block the light around us before opening and letting the light in and reaching your eyes.

A cameras shutter does the same thing but in reverse. Its closed to begin with (eyes shut). When you press the button to take your image, the shutter opens for a length of time (eyes open) before closing again (eyes shut) – the length of time the shutter remains open (eyes open) controls how much light reaches the sensor. Shutter speeds are represented at a fraction of seconds. 1/100 is a base level however depending on what you are capturing you may need to adjust this to a higher or lower level.

If you have a shutter speed of 1/500th of a second only a small amount of light reaches the sensor. If you have a shutter speed of 5 seconds, more light reaches the sensor because the shutter (eyelid) is open for a longer amount of time. I will demonstrate the differences in fast and slow shutter speeds in a separate blog post.


The function of the Aperture of a camera lens is also to control the amount of light that reaches the camera. It works in a similar way to the Iris of your eye. The wider your iris is, the more light enters your eye. In a lens, there are ‘blades’ that open and close to control the amount of light that passes through the lens. How ‘wide open or closed’ the blades are are measured in ‘f-stops’. An Aperture of F 1.2 means that the blades are not restricting light passing through the lens whereas an F-stop of F22 means that the blades have closed to only let a small amount of light pass through the lens. This is a very basic description of aperture, I shall go into more detail about Aperture in a separate blog post.

High and low Aperture

When shooting in manual mode, you have to make sure all three of these settings are correct. Often, changing one of the items in the Exposure Triangle will mean that the other two items will need to change to compensate. As you can imagine, this process means it takes a longer time to take a picture however the more you do this the quicker you get. When in ‘AUTO’ mode – the camera decides what the 3 settings needs to be, in manual mode – you choose the settings.

The correct ISO, Shutter Speed and Aperture is the KEY to a great images, whether its a fashion shoot or a picture of your family. Mastering the correct settings to get a clear sharp image will take time. Your first attempts with often be a combination of too dark, too bright blurry or out of focus, however, stick at it, think about what’s wrong and change your settings. Give it a go and show me your results

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