1. What is aperture?
Out of the three settings to adjust on manual mode, aperture is by far the most amazing. It is the secret to beautiful portraiture and blurry backgrounds!
When we talk about aperture, we refer to how wide the blades of a lens open. If the blades are wide open, a lot of light comes in and achieving a blurry background is made possible.
This image was taken with an aperture of f1.8.
2. How to set your aperture.
How wide your aperture can be set depends on each lens. Usually, lenses that can open very wide are more expensive as they require more advanced features. A lens that can open at f1.8 is an awesome start.
The numbers can be a little bit counter intuitive because the smaller the number, the wider the blades are opening. Hence, if you set your aperture at f1.8, the blades will open wider than if you set it at f4.5. So at f1.8 more light is coming in than at f4.5.
One thing to take into account when you set your aperture is how much of the picture you want in focus. Let's imagine you would like to take a picture of a flower and you only want the flower to be in focus, you can set a low aperture so you get a nice blurry background and only the flower is in focus.
3. Examples of pictures taken with a wide aperture.
This picture of my son's hands was taken at a very wide aperture: f1.8. Since I was very close to my subject only a very thin slice of the photo is in focus which gives it a very soft effect: you can almost feel the wind blowing.
With the second example, you can very clearly see that there is only one area that is in focus in the picture. To take this one, I got very low on the ground, chose a really wide aperture and focused on the leaves just in front of me. As a result, almost everything on this picture with the exception of the leaves on the foreground is blurry.
4. Examples of pictures taken with a more narrow aperture.
Conversely, if you are taking a family picture and you want to make sure that everybody is in focus, you will have to set your aperture a little bit higher.
For this fun shot, I set my aperture at f3.5, but I should have set it a little bit higher up (around f5) because we were constantly moving and the focus fell on the grass in the foreground (I always learn something from my mistakes!)
A narrow aperture is particularly convenient when you do street/landscape photography so you can have as many details in focus as you want.
The first picture was taken with an aperture of f3.5.
This one is f4.
The last one is f5.
5. Tip: the distance between you and your subject also affects how much of your images is in focus.
With experience, you will realize that how blurry or in focus your picture is also depends on how far you are standing from your subject. If you set your aperture at f1.8, for instance, and you are taking a very close shot of your subject, you will get a very small part of your photo in focus (my first photo is a good example). On the other end, with the same aperture, if you step back a little bit, you will get more of your subject in focus.
Manually setting your aperture is extremely rewarding. In order to obtain a blurry background, however, you will have to stay away from using your kit lens. You can read here what gear I recommend to get started.
I hope you find this useful!