Aperture Explained

In Essential Photography Skills and Tips by Dale Sinclair

Your camera’s aperture can be defined as the width of the opening in the diaphragm of a camera’s lens. The width of the opening is measured by using what is called f-stops as shown in the diagram below. And to confuse matters, the wider the opening, the lower the number – this is a rabbit hole I am not going to get into here, just know that this is the case.

The aperture opening manages how much light is concentrated, at the time the shutter is pressed, into your camera. This directly affects the depth of field or in other words, the plain of focus. Basically, how much three dimensional depth within your image is in focus.

A good example would be your own vision. When you look at a specific object, notice that the foreground and background are out of focus. Aperture allows you to control the depth of that focus plain – so with a really narrow aperture, everything could be in focus at once. Of course to the human eye this becomes somewhat unnatural, but allows a photographer to create a very unique experience for the viewer.

Not to forget – a lower f-stop, f1.4 as an example, indicates a very short depth of field but is considered to be widening the aperture. A broad depth of field requires a narrow aperture, f22 as an example.

The next step – what can you do with it?

Aperture is one of the 3 primary user controls in photography in addition to ISO and shutter speed. All 3 should to be considered when shooting manually. However, on SLR camera’s there is an Aperture Priority mode, typically indicated as “A” when selecting your shooting mode.

Aperture priority will allow you, the photographer, to only consider the aperture setting while the camera automates the other two. This is an excellent next step if you want to move away from scene selections and full automation.

With this mode selected you will be able to control your depth of field while leaving your camera to consider ISO and shutter speed.  Most particularly – giving you the creative control over what is in focus and not. So when you are doing close-up macros of tiny bugs or flowers, you can broaden the depth of field so you can get more than just the 2 front legs or that one petal in primary focus area. And when you want to only concentrate focus on a person’s eyes, you can decrease the depth of field so that the background and foreground is effectively blurred out of the image.

There is no amount of reading that will help you perfect your use of aperture. As long as you understand the principle of it, as I am trying to explain here, experience is priceless.

Learning assignment: To understand how changing your aperture will affect your photography, choose a subject like a pencil on a busy desk surface and use a wide aperture to concentrate the focus on to just the pencil and then take another photo with a narrow aperture to increase the depth of field so that it will take in as much as possible on the desk surface. Pick different subjects in different lighting conditions to learn even more. If you are using Aperture priority – you should take note of what the camera has selected as ISO and shutter speed. Otherwise, in manual mode you will find that you may have to increase the light intake quite a bit using a combination of ISO and shutter speed when expanding your field of focus.

Happy shooting! And if you haven’t already, read the ISO and Shutter Speed Explained articles. Comprehending aperture, ISO and shutter speed will help you shoot better photographs.