Figuring out how aperture works can be overwhelming if you’re new to photography. Take an in-depth look at aperture here and how this important aspect of photography can influence your photographs.
Words and Photography by Urth HQ
What is Aperture?
The dictionary says simply that aperture is an opening, hole or gap. Or more explicitly that aperture is “a space through which light passes in an optical or photographic instrument”.
Cameras and eyes are relatively similar instruments. The pupil of our eye acts as the aperture. Did you ever test this in a high school science class? The teacher would turn the lights off and on as we stared into the dilating and contracting pupils of our fellow science pals.
What the pupil is doing in this case is allowing more or less light to enter our eyes depending on the changing bright or dark environment. In photography, we do the same by controlling the aperture. In night photography, we may need to open the aperture wider to let more light in to achieve a well-exposed image. And vice versa for a particularly bright scene.
To Understand Aperture, You Need to Know About F-Stops
Before we go any further, we should quickly talk about what f-stops or f-numbers look like on your camera’s display and how to adjust aperture in camera.
Aperture is often referred to as wide or small, but it’s more technically referred to as f-stops or f-numbers. You’ve probably noticed the little ‘f’ on your camera’s display or in the viewfinder? It stands for fraction, because aperture is measured as a fraction of the focal length of your lens.
Here’s where it gets a little complicated, so let’s have a quick maths pop quiz.
If you’re shooting on a 50mm lens with your aperture set to f/2, how wide is your aperture opening in millimetres? The answer: 25mm (or close to an inch). Why? Because the f/2 value is to be read as the fraction, 1/2. And 1/2 of 50mm equals 25mm.
The fraction measurement is the same reason that f/4 is a bigger aperture than f/8… But how? f/8 is twice as big as f/4! If you’re splitting a pizza with your friends, would you rather ¼ (25%) or ⅛ (12.5%)?
Aperture plays such an important role in lens quality and creative capability that lens manufacturers include the maximum aperture in the lens name i.e. Canon 50mm f/1.8. In this instance, the f/1.8 aperture is referring to a fixed aperture, which may sound like it can only operate at one aperture, but actually means the aperture can function independently of the lens focal length and you’ll be able to shoot with the entire range of apertures all the way up to f/22 and beyond.
If you ever see a variable aperture listing in a lens name such as, Canon 18-55mm f/4-5.6, this indicates that the lens will shoot at f/4 at the shorter end of the focal length (18mm) and f/5.6 at the longer end of the focal length (55mm). Variable aperture lenses are generally less expensive for this reason.
How to Adjust Aperture in Your Camera
Setting the aperture or f-stop depends largely on the mode you’re shooting in. If you’re on a digital camera set-up shooting in auto mode, the aperture will be set automatically.
There are only two ways to manually set your aperture on a digital camera and that’s in manual mode (M on your camera dial) and aperture-priority mode (different between each camera manufacturer but most likely A or Av on your camera).
Whether in aperture-priority mode or manual mode, you’ll need to set your desired aperture using the corresponding dials or functions. Keep an eye out for the little ‘f’ as your aperture guide.
What Does Aperture Do?
Aperture affects a photograph in a number of ways but most notably through depth of field. From isolated subjects and blurred backgrounds to brighter or darker images, aperture is the key to unlocking your creativity.
HOW APERTURE AFFECTS DEPTH OF FIELD
When beginning photography, it may be useful to think in two different ways: landscapes and portraits. Both of these styles of photography most often employ two very different aperture settings that result in two very different outcomes in terms of depth of field. So, what aperture to use?
BEST APERTURE FOR LANDSCAPE PHOTOGRAPHY
Most landscape photographs appear sharp, with everything in focus from foreground to background. This is called a large depth of field and is used by photographers in landscape and architecture photography, for example, to communicate to viewers the grandeur of the entire scene from front to back and from side to side.
Common small aperture values for landscape photography and a large depth of field are f/11 – f/22.
World-renowned landscape photographer, Ansel Adams founded a club called ‘Group f/64’, a reference to the f-stop and the sharpness at which they recorded the American landscape. Side note: Adams and company photographed on large format film cameras which were capable of capturing a landscape at f/64 in incredible detail. Don’t do this at home! Modern digital cameras are at risk of loss of sharpness when approaching the f/22 mark.
WHAT APERTURE FOR PORTRAITS
On the other hand, most portrait photographs only show the portrait subject in focus with the background heavily blurred. This effect brings the subject forward out of the background so the viewer’s attention is immediately directed towards the photographer’s subject. This is called a shallow depth of field or shallow focus.
Common wide aperture values for a shallow depth of field are f/1.4 – f/5.6.
It’s all a bit confusing, right? As mentioned before, the larger the aperture, the smaller the number.
An easier way is to remember that the larger the aperture (i.e. f/1.4 – f/5.6), the larger blur you will have in the background or foreground. And the smaller the aperture (i.e. f/11 – f/22), the smaller amount of blur.
See this aperture chart demonstrating the difference between small and large aperture.
HOW APERTURE AFFECTS EXPOSURE
If adjusting aperture to achieve a shallower depth of field, you will also be opening the lens to allow more light to pass through and reach the sensor. Be careful to avoid widening the aperture too much and creating an overly bright image.
Having said that, there are a few ways around overexposing your image. One option is to relocate to a place where that isn’t as naturally light, so you can widen the aperture more than in bright daylight. If you need to shoot in bright light, another option is to use a Neutral Density filter, often referred to as an ND filter. ND filters are dark filters you place on the front of your lens to limit the amount of light entering your lens. This allows you to use wide apertures or long shutter speeds in bright light without the overexposure.
The shallow depth of field in the photo to the right below wouldn’t have been possible without an ND filter limiting the amount of light entering the lens. You can learn more about ND filters in our ND buyer’s guide.
SMALL APERTURE EXAMPLES
WIDE APERTURE EXAMPLES
What Aperture to Use
Picking the right aperture or f-stop doesn’t need to be tricky. Ask yourself what you’re trying to achieve with the shot. Shallow depth of field? Sharp image from front to back?
As mentioned, it may help to categorise the photograph into a portrait or a landscape initially as this will provide a ballpark for your aperture value.
As with all elements of photography, it’s a balancing act to achieve the right exposure and the desired artistic effect such as a shallow depth of field. Another factor to consider is the lens you’re using. If you begin to shop around you’ll notice that often the more expensive lenses are capable of reaching far greater aperture values such as f/1.4. Take a look at the markings on your lens as this will determine the parameters of your aperture.
“The best way forward in learning the art of aperture is to set your camera to manual mode.”
Aperture photography is crucial both from a technical standpoint and an artistic one. Mastering this foundational camera function is an important step in your photographic journey.
The best way forward in learning the art of aperture is to set your camera to manual mode. Or at least aperture-priority mode — a great way to set and forget the aperture, allowing the camera to create a balanced image through automatic shutter speed and ISO. The importance of aperture in photography is so great that you simply don’t want to hand this responsibility over to the camera.