What is lens aperture and how does it affect your images ?
Of all the settings on a camera, aperture is probably the one that intrigues beginners the most. Those values f/2.8, f/8, f/11 written on lenses or in menus seem abstract at first glance. However, once you understand what this setting actually does to an image, everything becomes much clearer.
Aperture affects two essential things: the amount of light that reaches the sensor and the area of sharpness in your photo. These are two parameters that radically change the look of a shot.
This guide explains the principle in simple terms, with concrete examples to help you know what to choose depending on the situation.
What is lens aperture?
Before talking about settings and specific situations, it’s important to understand what aperture actually is. There’s no need to delve into complex optical formulas. Once you have a mental image in your head, everything else becomes logical.
What is lens aperture in photography?
Every lens has a mechanism called a diaphragm. In practical terms, this is a set of blades that move to reduce or increase the amount of light passing through to the sensor. Think about your eyes when you step out of a dark room into bright sunlight. Your pupils shrink almost instantly to avoid being dazzled. In the evening, they widen to capture what little light is available. The diaphragm does exactly the same thing, except that you choose when and how.
This aperture is measured using a value called f-stop, denoted f/2.8, f/5.6, f/11, and so on. And this is where many beginners get stuck for the first time: the logic of the numbers seems backwards. f/1.8 is a large aperture. f/16 is a small aperture. As the number gets bigger, the aperture gets smaller. Once you understand this reversal, everything else becomes much simpler. The smaller the number, the more open the diaphragm is and the more light enters. That’s the only rule you need to remember.
How do I know the aperture of my lens?
This information is always available, provided you know where to look. On an interchangeable lens, it is engraved directly on the mount or lens body. It is found in the form ‘1:2.8’ or ‘f/2.8’ depending on the manufacturer. On a fixed lens camera, it is listed in the product specifications or on the camera body itself.
In the camera menus, the aperture value is displayed in real time as soon as you switch to aperture priority mode (A mode) or manual mode (M mode). It can also be viewed afterwards in the EXIF metadata for each photo. This data can be accessed from any photo management software or by right-clicking on the file from your computer. This is very useful for understanding why a photo is successful or unsuccessful after the fact.
On a compact camera such as the Kodak PixPro FZ55, the wide-angle aperture is F3.9. This value is fixed and managed automatically by the camera according to the shooting conditions.
What does an f/2.8 aperture mean for a camera lens?
f/2.8 is what is known as a fast aperture. In practical terms, this means that the diaphragm can open wide enough to let in a large amount of light in a fraction of a second. This is a considerable advantage in situations where there is a lack of natural light, such as indoors, in the evening, at sunset, or in a concert hall.
The f/ value is actually a mathematical ratio between the focal length of the lens and the diameter of the open diaphragm. f/2.8 means that the diameter of the aperture is equal to the focal length divided by 2.8. The smaller this divisor, the larger the physical aperture. This is why an f/2.8 lens is larger and heavier than an f/5.6 lens with the same focal length. It physically contains a larger aperture.
In photography, f/2.8 is often considered the threshold at which a lens is considered fast. Lenses that go down to f/1.8 or f/1.4 are even faster, but also more expensive and bulkier. For most photographers, f/2.8 represents a good balance between low-light performance and reasonable size.
Which has the larger aperture, F2.8 or F11?
This is the most common confusion among those new to photography. As explained above, the answer is f/2.8. And yet, instinctively, we tend to think that 11 is larger than 2.8.
To avoid making this mistake again, here’s a simple mental image. Imagine that the f/ number is the denominator of a fraction. f/2.8 is equivalent to 1/2.8 and f/11 is equivalent to 1/11. Now, 1/2.8 is much larger than 1/11. The larger fraction corresponds to the larger aperture.
Another way to visualise this is to think of a door. f/2.8 is a wide-open door. f/11 is a door that is slightly ajar. Light passes much more easily through a wide-open door. This is exactly what happens inside the lens depending on the f-number you choose.
How does aperture actually affect your photos?
Understanding the principle of aperture is good. Seeing how it actually changes an image is what makes the setting really concrete. Aperture affects two very distinct visual dimensions: the brightness of the photo and the area of sharpness. And depending on what you’re photographing, one or the other takes on greater importance.
Which is the best option: a small or a large aperture?
To be honest, there isn’t one. It all depends on what you want to achieve.
A large aperture (f/1.8, f/2.8) lets in a lot of light. It allows you to shoot in difficult conditions without raising the ISO to levels that degrade the image. It also produces a pronounced background blur, known as bokeh. This is the effect we want in a portrait. The face is sharp, while the background dissolves into a soft blur that highlights the subject. This aperture is also the best choice for a close-up photo of a flower with an indistinct garden background.
A small aperture (f/8, f/11, f/16) does the opposite. It reduces the amount of light entering the lens, but extends the area of sharpness over a greater distance. This is what we want for a mountain landscape where we want the rocks in the foreground and the peaks on the horizon to be sharp at the same time. The same applies to architectural photography, a group of people lined up at different distances, or any scene where depth is important.
In practice, ask yourself one question before choosing: do I want to isolate my subject or keep everything in focus? The answer will directly guide your choice of aperture.
At what aperture is my lens sharpest?
Contrary to what one might think, a lens is not at its sharpest at its widest aperture. At f/1.8 or f/2.8, optical aberrations are more noticeable. There is a slight loss of contrast at the edges and imperceptible softness in the centre. This is not a serious flaw, but a physical reality related to the lenses.
Most camera lenses achieve their maximum sharpness between f/5.6 and f/8. This is known as the ‘sweet spot’, the area where aberrations are reduced and diffraction has not yet set in. This is because, at the other extreme, closing the aperture too much beyond f/16 causes an optical phenomenon called diffraction, which slightly softens the image.
To find your sweet spot in practice, the test is simple. Photograph the same fixed, detailed subject (a brick wall, a page of text laid flat) at different aperture values, keeping the rest of the settings the same. Then compare the files on your computer screen by zooming in on the areas of detail. The value that gives the most precision and microcontrast is your sweet spot. This test works for any lens or camera.
Aperture and depth of field: the direct link
Depth of field is the extent of the sharp area in a photo. And aperture is the main factor that controls it.
Here are two real-life situations to help you visualise this.
An outdoor portrait. You open to f/2.8 and focus on the eyes. The eyes are sharp, the rest of the face begins to blur slightly, and behind the person everything becomes a blurred mixture of colours. The depth of field is very shallow. This background blur is not an accident; it is exactly what we want to achieve in order to separate a face from its surroundings.
Now imagine a family photo. Two rows of people, some two metres away, others almost four metres away. If you keep the aperture at f/2.8, the people in the background will be blurred and the photo will be ruined. By switching to f/8, the area of sharpness extends enough to cover both rows. Everyone comes out sharp, regardless of their position in the frame.
The Kodak PixPro AZ528 opens at F2.8 in wide angle. On a 1/2.3″ sensor, the background blur remains subtle, but as you get closer to the subject, the separation effect becomes clearly visible. And when you extend the focal length on this 52x zoom, the optical compression further enhances this result, making it a setting worth exploring for portraits taken from a distance.
Which aperture should you choose depending on the situation?
The good news is that with a few simple guidelines, the choice quickly becomes instinctive. Here’s how to approach the most common situations.
What aperture should you choose for a photo?
There is no universal value, but there are reference ranges depending on the type of photo you want to take. Here are the most useful ones to remember.
For a portrait, aim for between f/1.8 and f/2.8. The goal is to isolate the subject against a blurred background while keeping the face in focus. The wider the aperture, the more pronounced the background blur will be. Be careful, though, because at f/1.8, the depth of field is so shallow that even a slight movement can cause the eyes to fall out of focus. f/2.8 is often the best compromise for a portrait in motion.
For a landscape, f/8 to f/11 is the ideal range. It guarantees extended sharpness from the foreground to the horizon while remaining in the sweet spot of most lenses. This is the value to keep in mind when photographing a wide scene.
For architecture, f/8 to f/16 works well. The straight lines and fine details of buildings benefit from a large depth of field and maximum sharpness. Below f/8, the edges of the image may lose some sharpness depending on the lens used.
For night photography, f/2.8 to f/4 allows you to capture enough light without slowing down the shutter speed too much. This is often the best starting point before adjusting the ISO according to the scene.
For macro photography, return to f/8 to f/16. In very close-up shots, the depth of field becomes extremely shallow even at f/5.6. Closing the aperture slightly allows you to keep a sharp portion of the insect or flower you are photographing.
Aperture, ISO, and shutter speed: the exposure triangle
Aperture never works alone. It is part of a three-parameter system called the exposure triangle, along with shutter speed and ISO sensitivity. These three settings are interdependent: changing one often requires adjusting the other two to maintain proper exposure.
Here’s how they interact in practice. You open the aperture to f/2.8 to let in more light. If you don’t change anything else, the photo will be overexposed in bright sunlight. To compensate, you can increase the shutter speed to reduce the exposure time, or lower the ISO to make the sensor less sensitive to light.
Conversely, by closing to f/11 indoors, the amount of light entering is reduced. To avoid getting a dark photo, you will either have to slow down the shutter speed (with the risk of motion blur) or increase the ISO (with the risk of digital noise).
Understanding this triangle means understanding manual mode photography. Each setting has an effect on the image beyond exposure. Shutter speed influences movement, ISO influences grain, and aperture influences depth of field. Mastering all three together gives you total control over the look of your photos.
Aperture, a simple setting that changes everything
Aperture is one of those settings that seems complex from a distance but becomes obvious once you start using it. A small number means lots of light and a blurred background. A large number means extended sharpness and the entire scene in focus. Once you’ve grasped this principle, it will stay with you forever.
What really makes the difference between a decent photo and a great photo is often this kind of conscious choice before you take the shot. You don’t need expensive equipment to start mastering aperture. Just switch to aperture priority mode, try out a few different settings on the same scene, and see what changes.
