Hi, my name is Rob Barron. Welcome to my series called Getting to Know Your Camera. Today, we are going to look at the subject of depth of field.
It sounds like it should be something complicated and a lot of people coming into our home they think it is. That the purpose of my tutorial today is top show you that it is not complicated. It is not something to be afraid of and it can become your very best friend in photography.
When you look at a picture we often talk about the subject. That is obviously the main part of the picture that we want to look at. And we might talk about the back ground and the foreground. The background of course is everything behind the subject. The foreground is everything in front of the subject. But to get all of that into focus would require you to have quite a large depth of field.
If you only wanted the main subject to be in focus and have the foreground and the background out of focus then that would require a shallow depths of field. So, the field in your photo is the area of distance home camera that is in focus. If you move forward or behind that field, things will become progressively more out of focus. So, depth of field can be used to enable our picture to feel like it has got some depths to it because if your subject is nice and sharp but the background is blurred, then your subject will be like full within the frame and it will give you almost the three dimensional effect and then it will look really good and deep. But if it is a wall in focus then it won’t look as good. Let us have a look at that in practice.
Now, I have taken some photos of some apples. Now, I have four green apples, one red apple. I would put them in a line and I want the red apple to be the most important part of my picture. If I use a deep depth of field, that is allowing a lot of area to be in focus. You will see that actually most of the apples are in focus and even the background is in focus as well. And it all looks a little bit messy.
However, if I reduce the depths of field right down, I can focus on this apple, have this nice and sharp and everything else even the apple is in front of and behind are blurred. And you will notice the background now is completely blurred and does not interfere with our picture. It does not look so busy. And all our attention is focusing onto this apple. So, that is what depths of field is all about.
However, you might be asking yourself “How do I change it?” You cannot change the camera to be out more out of focus or in focus because you have got to keep your subject in focus. You are going to focus your camera or you are going to use in order to focus, it is up to you. And you will focus on your subject. But how much of the rest of the picture is out of focus will be down to your aperture.
Now, aperture is the little iris inside the lens just like the iris in your eye which opens and closes to allow more or less light into the camera. Now, the wider the aperture the smaller the number on your camera, it goes down to like F1.8 or F2.8, F4, these are the stops. We call them stops going up and up. You will notice it is a low number wide aperture. But if we take it up to the other end of the scale, the lens that would go to my camera here goes to F22. And F22 is small, the tiny iris. And that actually gives us large depths of field.
So, let us just check that again. F2.8, the wide aperture gives us a shallow depth of field. Subject in focus, everything else be much more out of focus. If we go the other way to F22 we have a narrow aperture but we have a large depth of field, foreground, through to the background are much more in focus.
If you are doing like a big landscape scene, you would want the foreground and the background often to be in focus. And so we try and go for a small aperture. That is the higher numbers. But if we are doing other photos, we might want to get that narrow or shallow depth of field.
How do we change it? Well, your camera might be different to mine. This is a Canon 40D and they all operate in the same way. They just maybe change the button but they do it with. Now, what I am doing is I am going to adjust with this wheel here and this will adjust my aperture when it is in AP mode. Okay, Av means aperture priority. I am setting the aperture; the camera is setting the shutter speed. Okay.
As I change this wheel, you can see the figure here and I am just pointing that out to you now with a little comp stick. As you look at the moment you can see it says F2.8. F2.8 is a very wide aperture but as I turn the wheel, I am changing it in what we called half stop so going up through the apertures, the numbers are getting higher but the window is getting smaller. Okay, so we have gone from F2.8 turn, two click clicks takes us to F4 and we carry on through to F5.6, 8, 11 and up to F22. And F22 of course is very narrow but with a wide, deep depth of field. But what I want for the purpose of this photo is to get enough a shallow depths of field.
If we look at these videos, DVD sitting on my shelf I could take a photo with a deep depth of field with a large number aperture, so F22. But you can see that all of the videos are sharp. They are all in focus. If I was trying to tell you about one video, let us say this one here. I would want the camera to be focusing sharp on this one but I want the others to be more out of focus. So, down to F2.8 and look at the difference, now, you can see that my focus is on just this video. The others are burred and you would know by looking at it. They are not important. This one is.
And we can use that for all of our other pictures in different ways. Portraits, take a photo of a person, have the background completely out of focus, it will give a nice depth and they will stand out beautifully. Take a look at this picture with my little statuette that I have here. Now, I have taken a photo of this with this curtain behind me using a narrow aperture, that is the deep depth of field and you will see that it is all in focus including the pattern on the background here. We stop and look very good.
But look at this photo. This is with the wide aperture F2.8 and the shallow depths of field. The face is in focus, everything else even part of the statue is out of focus but the background is now blurred and is not interfering and so the photo is sitting forward and giving you that nice depth to the picture. It is standing out and not being distracted by the other things that you can see there. And that is what depths of field is all about.
Now, remember we are talking in the extremes from F22, right the way down to F2.8. But there are stops all the way down. And so if you want a medium depth of fields then you can go for F8 or F11.
Now, here is something you should know. The point of focus, let us say our main subject here we got my finger. The field, the amount of area that is in focus stretches one third in front of the subject and two thirds behind the subject. That is the way you need to think about it. So, this area here is going to be in focus. As long as I focus somewhere in this area, I am going to be getting something that is nice and sharp. But if I focus right away back here, then my finger will be completely out of focus and what would it look like.
So, you can get a shallow ordinary depth of field and you can choose how much you want by just selecting the aperture accordingly. Look at these lovely pictures and stamps. You can see that it is a little abstract picture and the very front part of these stamps are nice and sharp and focused. But those stamps which are a bit further behind, they are completely blurred.
And look at this little toy soldier. These two photos by the way is a courtesy of a friend of mine called Fiona, a very good photographer. And you will see that this picture, the toy is very, very sharp and it really stands out. There are other toys behind it. But they are not the part of the subject. We want them to be there but we do not want them to interfere with the main subject. But that main subject is able to really stand out because she has used a shallow depth of field, a wide aperture F2.8, F4 that area.
So, that is really all hat is involved with depths of field. It is not complicated but go away and try it. And assume that you can manipulate this for your own purposes so that your pictures look just how you want them to look. And you can really make those subjects really stand out. I hope that has helped you to understand what depths of field is all about. I look forward to seeing you again.
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