Aperture refers to the diameter of the opening of a lens’ diaphragm at the moment a photo is taken. The larger the aperture, the greater the amount of light your camera will receive. Aperture not only influences the exposure quality of your photos, it’s fundamental for obtaining the right depth of field.
Aperture and the «f»'s
The aperture of a lens is expressed using the letter "f", followed by a number (i.e. f/4.5). Depending on the lens, it usually varies between f/1.8 and f/22. This system often leads to errors for beginners, because the higher the f number is, the lower the aperture will be. Conversely, the lower the f number, the higher the aperture. So, f/1.8 constitutes a higher aperture than f/22.
Using aperture to adapt to light
With a high aperture (and thus a low f number), you can let in more light, which is especially handy for taking photos in poorly lit environments, such as indoor spaces.
Using aperture to control depth of field
The ability to change aperture means you can also change the depth of field, that is, the clear and fuzzy or blurred portions of your photo. The larger the aperture (low f) is, the smaller the depth of field will be, and vice versa.
To get a good outdoor shot, you should absolutely use a low depth of field (low f), which keeps your portrait clearly isolated and the background blurred or fuzzy. Doing so brings your subject to the foreground while ensuring the viewer isn’t distracted by the background since it will be blurred. This technique is also used for culinary photography and macrophotography. To photograph a landscape or a building, you must choose a small aperture (high f) to get a high depth of field and a clean shot.
- Landscapes, wide scenes, architecture: high depth of field/high f/low aperture
- Portraits, close-ups, focusing on an element: low depth of field/low f/high aperture
How can you adjust aperture?
To adjust the aperture, you have two options: manual (M) mode, or aperture priority mode (Av or A).
- In manual mode, hold down the "Av" button before turning the dial. Adjusting the aperture to play with the depth of field will influence the exposure. You should therefore adjust ISO sensitivity and the shutter speed according to the lighting conditions of your subject.
- Aperture priority mode (Av or A) is recommended, especially for beginners. It allows you to play with aperture and depth of field without having to worry about shutter speed or ISO sensitivity, which are set automatically by your camera.