Aperture is one of those specs that a lot of us know to be relevant without understanding the reason. Grasping this concept can be quite helpful even for those who are satisfied with low-key photography, as it allows you to have more agency over your snaps.
To put it simply, a wider aperture translates into more light entering the lens and reaching the image sensor – think of it like your pupils, which get bigger to allow more light to come in. The most obvious advantage of a wider aperture is the ability to take photos in darker environments; what is not so simple is the fact that a lower number means a wider aperture. Aperture is measured in f-stops, and as an example, an f/1.4 aperture can let more light in than an f/2.8 aperture. The reason behind this seemingly illogical notion is that the value represents the lens' focal length divided by its opening size – so a smaller f-stop indicates a broader opening.
The concept of aperture is closely linked to other specs such as ISO and shutter speed. While the former designates the image sensor's sensitivity, the latter refers to how long the camera sensor is exposed to the light that passes through a camera's "pupil." A combination of high shutter speed and narrow aperture could result in underexposed images, whereas lower shutter speed, coupled with a wide aperture, may produce overexposed and blurred shots. Considering the same relationship, a wider aperture implies that shutter speed can be faster, as more light enters the lens in a shorter amount of time.
Aperture is also connected to the depth of field: the wider the aperture, the shallower is the depth of field, which translates into more focus on a subject and background blur. This is generally great for portraits, but when focusing on landscapes, you may consider a narrower aperture value for a broader sharpness area.
The unstoppable progress of smartphone photography includes impressively wide aperture values, which makes for professional-looking photos with the pleasing bokeh effect (shallow depth of field and blurred background) and less blur where you don't want it. Although cameras and smartphones may have the same aperture values, results are still not comparable, especially when it comes to depth of field.