As goes without saying but it always gets better when you say it, a quick reminder. Aperture is one of the 3 parameters that influence the exposure of a photo.
It corresponds to the opening diameter of the diaphragm when triggered. If you remember the previous article, for example, we compared it to the size of the window.
How do we know which opening we are going to use?
The aperture is measured in number f. On your device, this registers as “f / number”. For example f / 3.5 or f / 22. Where a lot of novice photographers get lost is that f / 3.5 represents a larger aperture than f / 22 for example! It would be useless to go into technical details, but remember that:
the higher the number f is large, the more the opening is small
the higher the number f is small, the more the opening is large
In fact, it’s just like a fraction: 1/4 is smaller than 1/2. But as there is an f, it is not so intuitive for everyone, but hey, it is like that!
If you take a good look at your lens, you will find an inscription like 18-55mm 1: 3.5-5.6 The “1: 3.5-5.6” actually represents the maximum aperture of your lens at its extremes of focal length (or zoom if you prefer). I know, I speak a little Chinese, so let’s see what that fits in the case of this lens.
Here, the lens can therefore open maximum at f / 3.5 at 18mm and maximum at f / 5.6 at 55mm. This is because on these kit lenses, the maximum aperture changes with the focal length (there are also lenses that have a constant aperture, but they are generally both more expensive and of better quality). Keep that in mind, we’ll come back to that.
How to adjust the opening?
You can modify it in two different modes: manual mode (M) or aperture priority mode (Av or A). (for details, see the article on camera modes )
Manual mode (M)
In manual mode, if you want to change the aperture you need to keep the button “Av” or “+/-“ on your device down, and turn the dial. ( On some more high-end cameras, there are 2 dials, one of which controls the aperture, and the other the shutter speed ).
Remember that changing the aperture will change the exposure, so you may have to play on one of the other two pillars to maintain normal exposure. Having said that, I do not recommend trying to manual mode until you are familiar with the 3 elements of the exhibition.
Aperture priority mode (Av or A)
Aperture priority mode is aptly named: when you use it, your priority is adjusting the aperture. You will therefore only adjust the aperture (with the dial), and the camera will do the rest, namely adjust the shutter speed, and the ISO if you have left ISO at auto.
So you will logically ask me what is the point of adjusting the aperture, apart from modifying the exposure?