Photography Camera Aperture Explained

Roberto Blake

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Aperture is part of what photographers refer to as the Exposure Triangle, along with ISO and Shutter Speed. Aperture is a popular topic of discussion among both amateurs and professionals in photography because it either adds dimension to an image by separating a subject and background via shallow depth of field, or it can bring everything into tack sharp focus.

Shot at ISO 200 F/7.1 1/160 by Roberto Blake

Aperture Priority on a DSLR

Many beginning photographers who still haven’t quite moved away from Auto mode to Manual, usually use Aperture priority as a half-way step. When I first started using DSLR cameras, I used this method to gain more control over the look of my images, and I learned a lot more about digital photography by doing so.

What is Camera Aperture?

Aperture is the hole within a camera lens through which light travels to reach the camera sensor. It’s very similar to how the human eye works. The amount of light that reaches the retina in our eyes is limited by the size of pupil, which is why your pupils become wider in low light situations to compensate. It is the same with camera aperture in lenses, and why wide aperture lenses are used for low light situations in photography.

Shot at ISO 200 F/2.8 1/125 by Roberto Blake

What Do Aperture F-Stop Numbers Mean?

In photography, aperture numbers are called F-Stops. This is a way of describing the aperture (how opened or closed it is), and how much light it allows in. A smaller f-stop means a larger aperture, while a larger f-stop means a smaller aperture. To most people this seems backwards since F/2 is larger than f/8. I prefer to think of F numbers as slices of a circle or pizza, F 2 or 1/2 of circle is more than F 8 or 1/8 of a circle.

Image from Wikipedia.com

I Explain Aperture More in This Video

Lenses and Aperture

There are two types of lenses, fixed aperture (often called prime lenses) and variable aperture lenses found among lenses with zoom capabilities. Most kit lenses that come with a camera are variable aperture lenses. What this means is that when you zoom out on a kit lens to 18mm, the aperture will be f/3.5 but when you zoom fully in to 50mm it will be f/5.6. There are zoom lenses among the professional tier of lenses that have fixed apertures, such as the 70-200mm f/2.8 lenses among Nikon, Canon, and Sony. These lenses tend to be considerably heavier and more expensive.

Aperture and Depth of Field

Aperture controls Depth of Field in your images. Depth of field refers to where your image is sharp. A popular look is shallow depth of field which can be achieved with a Wide Aperture like F/1.8, but it also controls how much light is being let in through the lens. A smaller or more narrow Aperture like F/16 will give you an image where the background is very detailed and in focus. This could be good for architecture and landscapes, or when shooting large groups.

Shot at ISO 800 F/2.8 1/160 by Roberto Blake

When shooting portraits for photography or video where you want to separate the subject from the background, shallow depth of field and shooting with a wide aperture is ideal.

To compensate in photography you can use a lower ISO, (e.g. ISO 100 or 200) and a higher shutter speed.

If you are shooting DSLR Video in Daylight with a wide aperture, a faster shutter speed will not be an option so you will need to make use of an ND (neutral density) Filter or a Variable ND Filter.

Understanding How Lens Aperture is Marketed

Lenses are typically marketed by their maximum (lower f number) aperture, for example F/1.4 and F/1.8. The reasoning for this is the maximum aperture allows you to shoot at a faster overall shutter speed. Often prime lenses are referred to as fast lenses for this reason.

The maximum aperture number tends to be more important than the minimum aperture number for most photographers. The maximum number tells you that more light can pass through the lens, which means the lens will perform better in low light. The minimum aperture number tends to be between f/16- f/22, which are rarely used outside of landscape photography.