For this video, we asked Jean-François Landry, trainer and advisor at Gosselin Photo Vidéo in Quebec City, to explain in less than two minutes what the diaphragm aperture is, which is one of the three parameters that constitute the exposure triangle and influence the light entry.
What is the aperture diaphragm?
How to determine it? What will be the impact of this setting?
First of all, you need to know that the diaphragm is a component of the lens that allows you to control the amount of light entering the camera.
You can set your camera or your lens to obtain a small or large aperture, so as to dose the entry of light, as you wish.
For example, an aperture of f/2.8 is very open. An aperture of f/32 is very close. This may seem contrary to logic... It is quite logical!
You have to understand that these are fractions.
When we talk about f/4, it's a quarter. When we talk about f/16, f/22... f/32, it's 1/32. That's why a very small aperture will have a very large number.
You may need a small aperture if you are doing landscape photography and have a lot of light.
On another hand, if you want to open the diaphragm, it is probably because you are lacking light. In this case, you can work with an aperture from f/2.8 to f/4, for example; it brings in more light and you become more comfortable in an environment where the light is problematic.
So, the first incidence of the diaphragm, of the opening of the diaphragm, namely the size of the hole: it is the entry of light.
La seconde incidence est, et c'est très important : la profondeur de champ.
Lorsqu'on ouvre le diaphragme, on fait rentrer énormément de lumière. f/2.8, ça le fait bien, mais ça va rendre le fond de l'image très floue. On se sert de ça généralement en portrait.
We like to open the aperture for portraiture, while we prefer to close it for other types of photography.
Choosing a smaller aperture makes the front and background of the image very sharp, very very sharp, almost as sharp as the subject itself. This is the type of setting that is usually preferred for landscape or architecture where we like to have all parts of the image in focus; those that are far away as well as those that are closer, for a photograph that is more documentary.
In short, a large aperture (e.g. f/2.8) lets in a lot of light, giving little depth of field, and therefore, a lot of blur in front and behind your subject.
A small aperture (e.g. f/32) prevents your sensor/film from being overexposed to a very bright environment, while providing a large depth of field, ensuring a comfortable focus area on both close and distant content.
The diaphragm influences the light entry, but also the image rendering. It is therefore necessary to meticulously adjust this setting in order to obtain the image you have in mind.
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