What’s aperture all about?

Let’s take a refresher on the role of aperture when it comes to making images

Changing the aperture of your lens is one of the fundamentals of photography, allowing you to alter both the exposure of a picture and how much of it appears sharply focused.

The aperture itself requires little explanation: it’s a physical hole in the lens that light passes through to reach your camera’s imaging sensor. In most lenses, this hole is formed by overlapping blades that create a diaphragm, which regulates how much light is let into the camera.

Large apertures let more light into the camera; small apertures reduce the amount of light. That bit is easy enough to understand. What’s more confusing is the set of numbers that represent the size of the aperture.

The first thing to consider is that f-numbers aren’t a physical measurement of the diameter of the aperture. Instead, they represent the ratio between the diameter and the focal length. An aperture of f/4 actually means the focal length (f) divided by four, and an aperture of f/16 means the focal length divided by 16. Using this rule, you know that when a 400mm lens is set to f/8, for example, the diameter of the aperture is 50mm.