Aperture - What's the Focus?

Controlling the Aperture on Your DSLR Camera

Many photographers struggle with some of the most basic and fundamental concepts of exposure in photography, getting frustrated with not being able to take good pictures. Unfortunately, some get stuck in automated modes, preferring to let their cameras decide everything for them.

In order to help you explore the full potential of your camera gear, we will start by exploring one of the pillars of photography – aperture (the other two being ISO and Shutter Speed).

Without a doubt, aperture is the most important of the three settings, simply because it affects so many different variables of an image. It can add dimension to your photographs by blurring the background, and it also alters the exposure of your images by making them brighter or darker. In this article, I will cover everything you need to know about aperture, all in very simple language.


So what is Aperture? Aperture is a hole within a lens, through which light travels into the camera body. Say whaaaaat?

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 your aperture. You can shrink or enlarge the size of the aperture to allow more or less light to reach your camera sensor.

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 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.

Take a look at the images above for a better visual of how aperture affects exposure.

The graphic below might give you a better representation of how aperture affects your photos.


The other critical effect of aperture is something known as 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.

In the image above, only the baby and his sister are in focus due to my careful choice of aperture. Specifically, I used a large aperture here, which naturally results in a shallow focus effect. If I had chosen a much smaller aperture, the entire photo including the parents in the back would have been sharp, without any clear out-of-focus background.

One trick to remember this relationship: a large aperture results in a large amount of background blur. This is often desirable for portraits, or general photos of objects where you want a blurry background. For example, one reason why the photo below works well is because it has a blurry background and desirable bokeh (out of focus lights). On the other hand, a small aperture results in a small amount of background blur, which typically is ideal for things like landscapes and architectural images.


Aperture plays a big role in photographing groups of people. The photo to the right was shot at f/1.8, which is too open for everyone in the group to be in focus. The boy in the middle is sharp, but as you look out from the center, the subjects become less sharp and more out of focus due to a shallow depth of field.

This photo below was shot at f/5.6, and you can see more of the subjects in focus just by closing the aperture more. A setting of f/5.6 is ideal for a group of

2-4 people. As you begin to close your aperture (making your f-stop number higher), you will produce a darker image due to less light entering the lens. Make sure you raise your ISO as needed (as I’ve done in these photos.

The final image shows the aperture setting used correctly. All of the kids are in focus, because there is greater depth of field. This photo’s aperture was set at f/11, which is ideal for larger groups. Remember, the larger the group of people, the higher your f-stop needs to be...less light will be entering the lens, which makes an outdoor setting ideal for taking group photos.


So far, we have only discussed aperture in general terms like large and small. However, every aperture can also be expressed as a number known as an “f-number” or an “f-stop.” Whenever you see an aperture value, the letter “f” will appear 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. For example, the camera below is set to an aperture of f/3.5.

One important part of aperture that confuses beginning photographers is that small numbers are large apertures and large numbers are small apertures.

For example, f/2.8 is larger than f/4 and much larger than f/11. Most people find this awkward, since we are used to having larger numbers represent larger values. Nevertheless, this is a basic fact of photography.


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.

As for depth of field, recall that a large aperture like f/2.8 will result in a large amount of background blur (ideal for shallow focus portraits), while apertures like f/8, f/11, or f/16 will help you capture sharp details in both the foreground and background.


Every lens has a limit on how large or how small the aperture can get. With some zoom lenses, the maximum aperture will change as you zoom in and out. For example, with the Nikon 18-55mm f/3.5-5.6 lens, the aperture shifts from f/3.5 at the wide end to f/5.6 at the longer focal lengths. More expensive zooms maintain a constant maximum aperture throughout their zoom range, like the Nikon 24-70mm f/2.8.


Aperture is clearly a crucial setting in photography and it is possibly the single most important setting of all. This is because depth of field and exposure have such major effects on an image, and your choice of aperture changes both of them.

Knowing how important aperture is, it shouldn’t be a surprise that, here at Urban Rhino Photography, we shoot in manual mode 100% of the time. We never want the camera to select the aperture for us. It’s just too important, and it is one of those basic settings that every beginner or advanced photographer needs to know in order to take the best possible images.

Hopefully you found that this explains the basics of aperture in a way that is understandable and straightforward. The next important setting to learn is ISO, so stay tuned for that post! In the meantime, check out our tutorial video giving you a more in depth look at aperture...

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