What is depth of field (DOF), and why does it matter?

So, what is depth of field and why does it matter? In this movie, we're going to talk about the what and the why. Let's begin with the what. Depth of field has to do with the areas of your image which are in focus or out of focus. If we take a closer look at this frame, you can see that I'm in focus, as is the sailboat in the background. And this will be the case, even if I stand up and walk forward towards the camera, you can see that we're still both in focus. That's because we have a lot of depth of field. And we can change our camera setting so that we have what's called a shallow depth of field. Let's take a look at what that would look like. So now, we're looking at this scene with what's called a shallow depth of field. So that I am in focus and the background is out of focus. And when using a shallow depth of field, you can also shift this around. Here, we can shift our focus so that the background is in focus and I am blurry and we can also bring it back. Well now that we have seen what a shallow depth of field looks like. Let's talk about how this actually works and to do that, we'll head outside. All right. Well we have stepped outside of the studio to talk about the concept of depth of field. As you can see in this scene, both Kelly and I are in focus. Yet what you can do with your camera, is you can change your camera settings so that you can have what's called a shallower depth of field. In this case, you can see there's just a small slice of this image in focus. If you increase your depth of field so that you have a greater or a larger depth of field that will open up that space and you'll gain more depth of field behind the subject than you will in front of. In this case, this gives space for the subject to step backwards if she wants to or she could also move forwards, as well. Pun intended. Here we are now on the field to talk more about depth of field. As we already know, one of the things that we can do is change our camera settings so that we have a shallow depth of field. And if we lower the f-stop even further, we'll have an even shallower area of focus. One of the things that can happen is the subject can move. If she steps backwards, for example, she'll look a bit blurry. What we need to do is to refocus. Another influencing factor is camera angle. If I have a higher camera angle, you can see how the area focus runs parallel to the sensor in the camera plane or the focal plane. If I have a lower camera angle, you can see how that'll affect the area of focus as well. All right. Let's head back to the studio. All right. So now that we've seen a little bit about how depth of field works. How do we create it on our cameras and lenses? Well, here I have a lens, which I took apart a few weeks ago, which was a lot of fun. And you can see I can control the iris or the opening on the front of the lens, so we can make it larger or smaller. Now, we can change that by changing our f-stop. If we have a lower f-stop number, like f1.2 will have a shallower depth of field. If we have an f-stop number like f22, we'll have a larger depth of field. And people like Ansel Adams used to shoot photographs at f64 so that everything from the foreground, all the way to the background was in focus and sharp. And in portraiture we tend to do the opposite. We like to use smaller f-stop numbers so that we can have our subject in focus and everything else a beautiful blur. And, you know, there's a word to describe the blurry area of a photograph and it's called BOKEH. It's a Japanese word which describes the area which is out of focus when you're shooting with a shallow depth of field. And in photography often a shallow depth of field replicates how we see the world. For example, do this right now for me. Hold your finger out in front of you and focus on it. What you'll see is that your finger is in focus and the background is completely blurry. Then move it closer. As you move it closer, the background will become ever more blurry. And in a sense, this is a shallow depth of field. Now our human eye sees the world this way and I think at the same time, so does our heart and our soul. In other words, let's say, that I'm in my back yard and all of a sudden I see my daughter running outwards me across the lawn. Well, I will focus in on her and everything else will be a blur. And in a sense, that's a lot like having a shallow depth of field. So, one of the reason why we use a shallow depth of field is because it allows us to create a unique look. It also gives us the ability to add feeling to our photographs. All right. Well now that we know a little bit about both the what and the why. Let's dig a bit deeper into how can actually control and create a shallow depth field and let's do that in the next movie.