Getting a nice camera is just the first step in taking great photos—you also need to learn how to use it and shooting on auto will only take you so far. There comes a point when as a photographer you should begin to experiment with your camera’s manual mode, and aperture settings are a key component of this. Aperture is often one of the most difficult concepts for people to grasp when they’re learning how their camera works, but it’s pretty simple once you understand it.
The first thing to understand when exploring your camera’s settings is the concept of exposure. Technically defined, in photography exposure is the amount of light per unit area reaching a photographic film (as with older film cameras) or in newer digital cameras the electronic image sensor. Exposure is important when taking pictures because it determines whether your photograph is too light or too dark. Photographic exposure is affected by three things: shutter speed, lens aperture, and ISO (sometimes called the exposure triangle). Since we are only talking about aperture settings today we will assume that your cameras shutter speed and ISO settings remain constant.
You can check your photo’s exposure levels using a histogram. All digital cameras have a histogram feature and you can find out how to turn it on in your camera’s manual. A histogram is a visual representation of light tones in your photograph, from the shadows, to the mid tones, to highlights. Using the histogram feature of your camera you can check if your photograph has any shadows that are too ‘clipped’ or too dark and to see if you have any highlights that are too bright or ‘blown out’. Clipped shadows are areas of pure black that contain no detail and blown out highlights are areas of pure white that also contain no detail. As a rule, you should avoid both clipped and blown out highlights in your photographs and you can do that by adjusting your aperture settings.
What is the Aperture?
Basically speaking, the aperture is ‘the opening in the lens. If you think of your camera’s lens like your eye the aperture would be your iris. Your iris automatically opens wider to let more light in when in darkness or gets smaller in bright light, letting less light in to your optic nerve. In fact, the mechanism in your digital camera that controls your aperture is called the iris. When you hit the shutter release button of your camera the iris opens and allows your cameras image sensor to catch a glimpse of the scene you’re photographing. The larger the hole the more light that gets in – the smaller the hole the less light. The aperture settings on your camera adjust the size of that hole and are measure in numbers called f-stops.
How to Set your Aperture
A f-stop (sometimes also called focal ratio or f-ratio) is the ratio of the focal length (the distance from the sensor to the rear of the lens) to the diameter of the aperture, i.e. it is the reciprocal of the relative aperture. Your f-stop settings will look something like this; f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8…. f/128. Lenses are marked with their widest possible aperture. If you see a lens that is a 50mm f/1.8, this means it’s widest aperture is f/1.8. Moving from one f-stop to the next doubles or halves the size of the amount of opening in your lens (and the amount of light getting through).
One thing new photographer’s often find confusing is that large apertures (where lots of light gets through) are given smaller f/stop numbers, and smaller apertures (where less light gets through) have larger f-stop numbers. So, f/2.8 is in fact a much larger aperture than f/22. It seems counterintuitive but familiarizing yourself with your camera and experimenting with different f-stop setting will help you get the hang of it.
Aperture Settings and Depth of Field
Another thing your camera’s aperture setting affects is depth of field. Depth of field (DoF) is one of, if not the most important concepts in photography. Understanding what Depth of Field is, and how to manipulate is somethings all photographers should aspire to. Depth of Field is defined as “the distance between the nearest and the furthest objects that give an image judged to be in focus in a camera”. In layman’s terms, it’s the distance between the closest and farthest objects in a photo that are in focus.
Some examples of varying depth of field in photographs look like this,
Using your Aperture Settings
Aperture and f-stop settings play a key role in developing depth of field in your pictures. Aperture affects how much light enters the camera as well as determines how much of the lens is being used. When the amount of light travels through a smaller section of the lens, the light cone narrows and extends, increasing your depth of field. As such, smaller apertures (larger f-stops) equals a larger depth of field. Conversely, the larger the aperture (smaller the f-stop) the narrower your depth of field. I find it’s easiest to remember that the lower the f-stop number, the more blur in the foreground and background of your pictures. This is especially important in macro photography when the photographer wants to use large aperture settings to ensure the viewers eye is focused solely on the object and the rest of the pictured is blurred out of focus to avoid distraction.