How does Aperture Work?
The holy trinity of photography is definitely aperture, shutter speed and ISO. The three work together to create your images, and all three control how much light the lens lets in to the camera. Today we’re going to discuss aperture – how to understand it, and how to use it to enhance your photography.
Put simply, aperture is the most visual of the three basic pillars. It can produce wonderfully blurred backgrounds, with only the main subject of your image in focus, or it can bring everything into focus from the nearest tree to the furthest hill in the same image.
Aperture is actually the size of the hole within your lens, which lets light into your camera. The larger the aperture, the more light you let into your camera, and vice versa.
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The Confusing Relationship Between f-stops and Aperture
Does the explanation of what aperture is sound simple? It is – but where it can get confusing is when you apply f-stops to the different sizes of aperture. An f-stop, also known as an f-number, is a method of describing the size of the aperture, and the misunderstanding can arise because a smaller f-stop number means a larger aperture, hence more light getting into the camera. A larger f-stop means a smaller aperture, meaning less light getting into the camera.
Most people are used to larger numbers representing more of the same thing, but in aperture and f-stops that’s not the case. If you consider that f/1.8 is larger than f/4, and much bigger than f/8, it’s easy to see the potential for confusion.
This chart below represents the size of the lens aperture and the corresponding f-stops:
Depth of Field: What it is, and How You Can Use it to Create Impact
Depth of field is basically using your aperture to control how much of the shot is in focus. The size of the aperture has a direct relationship to how much or little of your image appears sharp.
For instance, a large f-stop such as f/22 (which lets less light in than a lower f-stop) will give you an image with all the foreground and background in focus. Most landscape images are shot with a higher f-stop.
A small f-stop such as f/1.8, on the other hand, will isolate your subject from the background and blur everything that is not on that plane of focus. Think of close-up portraits where only the eyes are tack-sharp, and everything else gradually falls off into softness. A good example of that are the old-style Hollywood film star images from George Hurrell and Clarence Sinclair Bull. Food photography is another area where shallow depth of field is often used to separate food items from the background.
Wide Depth of Field
You can see in the image below how a landscape has been shot with a wide depth of field (large f-stop – small aperture)
You can see everything from the plants at the front right to the mountains at the back.
Shallow Depth of Field
This image of fruit hanging from the tree is a perfect example of shallow depth of field (small f-stop – large aperture)
The apple itself is in perfect focus, and some of the twig it is hanging from, but the focus starts to fade off with the leaf and twig behind the apple, becoming totally blurred in the background. This is how depth of field is used to effectively isolate a subject.
Creative Uses of Depth of Field
You don’t just have to focus on the subject right in front of you to use a shallow depth of field – it’s often used creatively to pick out one specific item in the middle of a line to separate it from similar or identical items, such as in the image below:
See how the jackets at the front are out of focus, leading gently in to the jackets that are sharp, then falling off again towards the back of the image? This can be a really effective way of using depth of field.
Don’t get caught up in thinking that landscapes can only be shot with a wide depth of field, with everything sharp front to back. Sometimes really beautiful landscape shots can be done creatively with shallow depth of field, such as the image below. Only the mid-foreground of the image is in focus, but you can still tell what the image is about, and I think the sharpness fading slowly in and then out to softness in the distance is beautiful.
Fast and Slow Lenses and What it Means
You may have come across the term ‘fast’ or ‘slow’ lenses before. Lenses have a limit on how large or small the aperture can get, and how much light they can let in to the camera. The maximum aperture of the lens (small f-stop) is important, because that is the limit on how much light your lens can let in. If your lens has a maximum aperture of f/1.2 or f/1.4 like this lens, then it is considered to be a fast lens because you can use a faster shutter speed with them. If your lens has a maximum aperture of, say, f/4.0, like this lens, it can’t let as much light in, so you would need to use a slower shutter speed to compensate in order to get correct exposure.
Fast lenses are also way, way more expensive than slow ones! They are very useful for shooting in low light situations, but you would only get the extra light f/1.2 could give at the expense of your wide depth of field, so they are not always the best choice, depending on what you are shooting.
Prime and Zoom Lenses
There are two main types of lenses. Fixed or prime lenses only have one focal length, such as a 50mm, while zoom lenses let you zoom in and out on a subject without having to move closer or further away like you do with a prime lens.
Prime lenses tend to give better picture quality than zoom lenses, because they have far less moving parts than zoom lenses. Prime lenses are also usually faster than zooms, meaning you can get maximum aperture of f/1.2.
Zoom lenses are very, very useful, especially for fast-moving subjects like sports or street photography, where you don’t have time or room to physically move in and out to capture the action.
Thoughts to Take Away
Hopefully, this article will have helped you to better understand aperture and its relation to f-stops.
You’ll get to learn about controlling shutter speed and ISO in later articles so you can take your camera fully manual, but in the meantime, try setting your camera to Aperture Priority mode. This will allow you to control the aperture settings on your camera, but the camera will still control shutter speed and ISO to help you gain correct exposure. Try experimenting with taking images at different f-stops, and isolating things with depth of field. Have fun!
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