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Aperture is one of the three light controlling aspects of photography (the other two being Shutter Speed and ISO), and is very important. In this article, we go through what you need to know about aperture and how it works.
An image captured with a wide aperture of f/1.8 isolates the subject
What is Aperture?
Aperture can be defined as the opening in a lens through which light passes to enter the camera. It is an easy concept to understand if you just think about how your eyes work. As you move between bright and dark environments, the iris in your eyes either expands or shrinks, controlling the size of your pupil.
In photography, the “pupil” of your lens is called aperture. You can shrink or enlarge the size of the aperture to allow more or less light to reach your camera sensor.
Aperture can add dimension to your photos by controlling depth of field. At one extreme, aperture gives you a blurred background with a beautiful shallow focus effect.
At the other, it will give you sharp photos from the nearby foreground to the distant horizon. On top of that, it also alters the exposure of your images by making them brighter or darker.
How Aperture Affects Exposure
Aperture has several effects on your photographs. One of the most important is the brightness, or exposure, of your images. As aperture changes in size, it alters the overall amount of light that reaches your camera sensor – and therefore the brightness of your image.
A large aperture (a wide opening) will pass a lot of light, resulting in a brighter photograph. A small aperture does just the opposite, making a photo darker. In a dark environment – indoors, or at night – you will probably want to select a large aperture to capture as much light as possible. This is the same reason why your pupils dilate when it starts to get dark.
How Aperture Affects Depth of Field
The other critical effect of aperture is depth of field. Depth of field is the amount of your photograph that appears sharp from front to back. Some images have a “thin” or “shallow” depth of field, where the background is completely out of focus. Other images have a “large” or “deep” depth of field, where both the foreground and background are sharp.
This photograph has a thin depth of field – a “shallow focus” effect.
In the image above, you can see that the girl is in focus and appears sharp, while the background is completely out of focus. The choice of aperture played a big role here. you use a large aperture in order to create a shallow focus effect. This helps bring the attention of the viewer to the subject, rather than busy background. If I had chosen a much smaller aperture, I would not have been able to separate my subject from the background as effectively.
A large aperture results in a large amount of both foreground and background blur. This is often desirable for portraits, or general photos of objects where you want to isolate the subject. Sometimes you can frame your subject with foreground objects, which will also look blurred relative to the subject, as shown in the example below:
On the other hand, a small aperture results in a small amount of background blur, which is typically ideal for some types of photography such as landscape and architecture. as In the landscape photo below.
If you’re a landscape photographer who wants everything as sharp as possible, it is often thought you should use your lens’s smallest aperture, maybe f/22 or f/32.
However at these very small apertures photos can loose a lot of sharpness due to diffraction.
Diffraction is actually quite simple. When you use a tiny aperture like f/32, you literally squeeze the light that passes through your lens. It ends up interfering with itself, growing blurrier, and resulting in photos that are noticeably less sharp.
What Are F-Stop and F-Number?
So far, we have only discussed aperture in general terms like large and small. However, it can also be expressed as a number known as “f-number” or “f-stop”, with the letter “f” appearing before the number, like f/8.
Most likely, you have noticed this on your camera before. On your LCD screen or viewfinder, your aperture will look something like this: f/2, f/3.5, f/8, and so on. Some cameras omit the slash and write f-stops like this: f2, f3.5, f8, and so on.
So, f-stops are a way of describing the size of the aperture for a particular photo.
Large vs Small Aperture
This is something you really need to pay attention to and get correct: Small numbers represent large, whereas large numbers represent small apertures.
For example, f/2.8 is larger than f/4 and much larger than f/11.
How to Pick the Right Aperture
Now that you’re familiar with some specific examples of f-stops, how do you know what aperture to use for your photos. If you’re in a darker environment, you may want to use large apertures like f/2.8 to capture a photo of the proper brightness (once again, like when your eye’s pupil dilates to capture every last bit of light): Lighter areas will allow you to use a smaller aperture of you wish e.g. f/8 and have more of your image sharp.
As for depth of field, recall that a large aperture value like f/2.8 will result in a large amount of background blur (ideal for shallow focus portraits), while values like f/8, f/11, or f/16 will help you capture sharp details in both the foreground and background (ideal for landscapes, architecture and macro photography).
If your photo is too bright or dark at your chosen aperture setting. Most of the time, you will be able to adjust your shutter speed to compensate – or raise your ISO if you’ve hit your sharp shutter speed limit.
Examples of Aperture Use
Now that we have gone through a thorough explanation of how aperture works and how it affects your images, let’s take a look at examples at different f-stops.
f/0.95 – f/1.4 – such “fast” maximum apertures are only available on premium prime lenses, allowing them to gather as much light as possible. This makes them ideal for any kind of low-light photography when photographing indoors (such as photographing the night sky, wedding receptions, portraits in dimly-lit rooms, corporate events, etc). With such wide f-stops, you will get very shallow depth of field at close distances, where the subject will appear separated from the background.
f/1.8 – f/2.0 – some enthusiast-grade prime lenses are limited to f/1.8 and offer slightly inferior low-light capabilities. Still, if your purpose is to yield aesthetically-pleasing images, these lenses be of tremendous value. Shooting between f/1.8 and f/2 typically gets adequate depth of field for subjects at close distances while still yielding pleasant bokeh.
f/2.8 – f/4 – most enthusiast and professional-grade zoom lenses are limited to f/2.8 to f/4 f-stop range. While they are not as capable as f/1.4 lenses in terms of light-gathering capabilities, they often provide image stabilization benefits that can make them versatile, even when shooting in low-light conditions. Stopping down to the f/2.8 – f/4 range often provides adequate depth of field for most subjects and yields superb sharpness. Such apertures are great for travel, sports, wildlife, as well as other types of photography.
f/5.6 – f/8 – this is the ideal range for landscape and architecture photography. It could also be a good range for photographing large groups of people. Stopping down lenses to the f/5.6 range often provides the best overall sharpness for most lenses and f/8 is used if more depth of field is required.
f/11 – f/16 – typically used for photographing landscape, architecture and macro photography where as much depth of field as possible is needed. Be careful when stopping down, as you will start losing sharpness due to the effect of lens diffraction.
f/22 and Smaller – only shoot at such small f-stops for good reason. Sharpness suffers greatly at f/22 and smaller apertures, so you should avoid using them when possible. If you need to get more depth of field, it is often best to move away from your subject or use a focus stacking technique instead.
This article was taken from photography life.com