The exposure triangle

The Exposure Triangle

Gaining the right exposure can be one of the trickier elements of photography, but understanding the three components that affect it will enable you to control it and achieve a perfectly exposed picture.

The Exposure Triangle

Getting the perfect exposure can be understood as being a triangle of three elements, with each one directly impacting, informing and influencing the other.

1. Aperture

How open the lens is and the amount of light that comes through it onto the sensor.

A narrow aperture such as F22 only allows for a small amount of light to pass through, whereas a larger or wider aperture such as F1.4 will let much more light in.

Choose the aperture based on what you want to appear sharp. A narrow aperture will provide you with sharpness from the foreground through to the background. If you want a softer foreground and background to create a photograph with a more ethereal look, choose a wider aperture.

2. Shutter Speed

The speed at which the shutter will open.

As well as the aperture, the shutter speed also has an impact on the amount of light that comes through onto the sensor. Your choice of aperture will normally inform the shutter speed you need; for example, if you choose to have a narrow aperture, you will probably need a longer shutter speed. If you've opted for a wider aperture, you can go with a faster shutter speed.

The shutter speed dictates whether motion will be captured clearly or blurred; a quicker shutter speed will allow you to capture motion sharply, whereas a slower shutter speed will mean any movement will appear blurry.

3. ISO

The sensitivity of the camera sensor itself.

The ISO level you choose will dictate the colour rendition and dynamic range in your photograph. ISO 100 is considered the standard at which you generally want to have your camera set to.

There are instances where you may need to increase the ISO. However, when you do this, there is a risk your photographs will become grainy or 'noisy', though most modern cameras will have the ability to shoot clearly up to an ISO of around 1600.

Use Pre-Visualisation Before You Choose Your Exposure

Before taking a photograph, it's helpful to consider and pre-visualise how you want it to look. Try asking yourself the following questions, as your answers can then be used to inform your choice of aperture, shutter speed and ISO.

• Where do I want the focus to be?
• Do I want the image to be sharp front to back?
• Would it work to have some soft areas?

Your Assignment

Go out into nature, and find a nice composition - ideally using a tripod. Take a series of different photographs of exactly the same frame, but manually adjust the aperture, going from the lowest setting to your highest. Do the same for shutter speed and then ISO.

Either print the photographs, or look at them on a big screen and observe the differences and nuances between them. Consider the impact of your choice of aperture, shutter speed and ISO on your images.