You know those pictures where only the flower is in focus, and everything else is blurry? Or the pictures where only the pen on the white paper is focused and the rest isn't? (yes I agree, that's a very bad example.)

So what about the picture where only the bride and groom's faces are nicely focused, and the rest of the world doesn't exist? Now that's more like it.

Before we start, let's have a look at 2 quick examples.



As you can see in the two examples above, only a specific subject in the two pictures is in focus, whereas the rest of the picture isn't in focus.
We're now going to understand how to achieve this effect easily.

First, we will try and understand what aperture is. Wikipedia tells us "An aperture is a hole or an opening through which light is admitted." Ok, great. Thanks for that info. It was really helpful.
Just kidding, there's a lot more to that quote, but it's not Wikipedia here.

We will try to understand what aperture is by using simple language and some basic terms.

The aperture controls the amount of light that enters your camera. The lower the aperture number is (1.4,2,2.8 and so on), the bigger the hole where the light comes in is, and therefore more light comes in. The bigger the number (11,16,22 and so on) the smaller the hole is, and therefore less light comes in. The numbers mentioned above are called F numbers and their purpose is to let us know how big or small our aperture is. The diagram below explains quite simply what I'm talking about.

After understanding the mechanics of the aperture, let's have a look at the things the aperture affects:

1. The amount of light:

As you already know, the aperture's size affect's the amount of light that goes through your lens and onto the camera's sensor. Let's just go over it once again-
A small F number means a bigger hole which means we get more light in.
A big F number means a smaller hole, which means we get less light in.

2. Depth of field:

I'm sure you've heard that expression before, but I'm not sure you understood exactly what it meant. I'm not sure I do either.
What I do understand is that by altering the aperture setting on your camera (higher or lower number) you change the depth of field of your picture.

That said, let me share my great knowledge with you.
Let's take the picture of the rose as an example. You might want to click on it to get a better look before we start.
As you can see, only the red rose is focused. This means the depth of field (known sometimes as DOF), is short. How do you achieve this effect then? You set the aperture to a small number, set the right shutter speed or use the aperture priority mode (don't forget to read about shutter and modes here), and take the picture. See the picture below as another example.


*Note that the DOF is changed not only by the aperture (large or small), but also by the distance to the object, and the lens you are using.
The equation is like this-
large aperture (smaller opening), results in a wider depth of field.
Small aperture (bigger opening), results in a lower depth of field.


Let's take a different example now. I'm sure sometimes you want to take a picture of a nice landscape. Landscape pictures have areas which are closer to the camera and areas which are much farther away. (The grass near you, the trees far away, and the sky way above). Ok, so let's think this through together. We know that by setting a small F number, only a certain part of the picture is sharp and focused, and that by setting a large F number, we get a larger amount of sharp areas. So what f number should you use for this kind of picture? A high f number. Get it?

And the last example will be the one when all you want to do is aim and shoot. People are standing about 3 meters away from you and behind them is a beautiful view. You want the people to come out nice and sharp, and the background behind them quite sharp as well. What aperture (f number) should you use? Think about the answer for a second before continuing.

The answer is- you set the f number in the middle. Between 8 and 11 will usually do the job.

3.Sharpness:
We covered this point in the previous topic, but just to make sure we understand it we'll go through it quickly again.
The sharpness is the area of the picture which is in focus. A landscape picture is usually sharp throughout the whole picture. A portrait picture is usually sharp only where the object is standing. An artistic photo has no rules.