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.
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.
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?
Depth of field is how much of the shot is going to be in focus, or in focus if you prefer. For simplicity :
if the depth of field is large, the majority (if not all) of the image will be in focus
if the depth of field is small, only a small part of the image will be in focus
How does this affect us? Well, there is a very intuitive relationship between f number and depth of field: the larger the number f, the greater the depth of field, and vice versa. One of the best advice I can give you is to hold onto this relationship.
You will understand, this has the consequence that if you want to increase the depth of field, you will in fact decrease the aperture (and therefore the light that enters the camera).
That said, depth of field is a bit more complex than that and is influenced by other factors. If you want to dig deeper, read the depth of field course ! 😉
When and how to use depth of field and aperture priority mode?
Typically, you generally want to have a great depth of field (large f-number) when photographing a landscape for example, or even a monument.
Conversely, if you are doing a portrait or photographing a flower for example, it can be interesting and aesthetic to use a shallow depth of field (small f number). This makes it possible to obtain a blurred background, and therefore to have only your subject in focus. This technique helps focus attention on your subject.
At this point, I hope you’ve understood correctly, but I’ll quickly summarize:
large aperture = f / small = shallow depth of field = portrait, flowers,…
small aperture = f / large = large depth of field = landscapes,…
If you’ve ever started playing around with aperture and therefore depth of field while reading this article, you must have noticed that when you change the aperture you don’t see the difference in depth of field in the viewfinder. In fact, your camera stays with the diaphragm wide open to aim and focus, and only closes it when the trigger is triggered.
But there is a fantastic tool: the depth-of-field control button. In fact its name is wrong, it should be called “depth of field visualization” instead. In fact, when you hold it down and change the aperture using the dial, you can see the effect of the change in aperture on the depth of field live in the viewfinder ! What to get exactly the blur you want!
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