The aperture is a component that controls the amount of light passing through the lens. Located inside the lens, it adjusts light intake by changing the size of its opening, as illustrated below.

The volume of light entering the camera is governed by aperture size and quantified using the F‑number. Standard F‑values include F2, F2.8, F4, F5.6, F8, and so on. As the F‑number increases, the aperture diaphragm closes, reducing light transmission. Conversely, a lower F‑number opens the aperture wider to admit more light. For instance, shifting the aperture from F8 to F5.6 doubles the incoming light. With all other settings unchanged, the same exposure can be maintained even if the shutter speed is halved.

Aperture also controls the range of the focused area, namely the background blur (bokeh) in an image. The comparison below demonstrates the relationship between aperture and blur. A smaller F‑number produces stronger blur on both foreground and background elements.

In general, a smaller F‑number allows more light into the camera and creates more pronounced background blur. Every lens has a minimum available F‑number, known as its maximum aperture. You can find this value on the lens barrel or within the lens specifications sheet. Lenses capable of very low F‑numbers are commonly referred to as fast lenses or large‑aperture lenses.

A Mode (Aperture Priority Mode)

A Mode (Aperture Priority Mode) lets users manually set the desired F‑number. The camera will automatically calculate and apply the appropriate shutter speed and ISO sensitivity to achieve correct exposure.

This mode is ideal when you wish to isolate a subject with blurred foreground and background, or capture deep focus across an entire landscape to keep both near and far objects sharply defined.

A higher F‑number narrows the aperture opening, which forces the camera to use a slower shutter speed. This increases the risk of motion blur caused by camera shake. If blurring occurs, try shooting again with a smaller F‑number.