What is aperture?

Aperture is the hole through which light travels into the camera. It sits behind the lens and in front of the sensor.

As you can see in this picture, the hole is created by lots of shutters.

Aperture

This enables the size of the hole to change. When the hole is larger, more light passes onto the sensor, and vice versa. Somewhat confusingly, a large aperture has a number like f/2.8 and a small aperture has a number like f/22.

What does aperture affect?

In low light situations, we need to use a wide aperture, like f/2.8. This will enable lots of light to get into the sensor. However, it also reduces the depth of field, meaning less of the photograph will be in focus. When we use a narrow aperture, like f/22, lots of the photograph can be in focus, from the foreground to the background, but less light will get into the sensor and the photograph will come out darker.

In cameras

Lenses on DSLRs have different maximum apertures. Some cameras only go up to f/3.5 and some go as far as f/1.2. That might not sound like a big difference but actually, it can make a huge difference if you are doing photography in low light. However, lenses with larger apertures (known as fast lenses) are more expensive. There are some great options though. The Canon “nifty fifty” is one example. It’s a 50mm lens, with a speed of f/1.8 and if you have a Canon DSLR it’s a great option.