Depth of Field (DOF)
so depth, the field is going to be changed by adjusted by changing the aperture on your lands. And so, in this example, you can see at 1.4 we're getting very, very shallow depth of field. The red lines indicate the front edge in the back edge of focus, and so we have very shallow depth of field. At this point. As we stop our lens down, we're gonna get a bit more depth of field. It's not a huge difference, but it's a bit more with each step along the way, and each lands is gonna have its own little set up as far as how much depth of field you get in here. And so this is for a 50 millimeter lens that you're seeing. Is this in this example here? And the most amount of depth of field will be able to get with this particular lands has stopped down it F 22 where we have a very large, great depth of field in this lands. Now I know when I first learned about this and thought about it, like pushing light to a smaller opening, why do we get more depth of field it doesn't make logical sense. I do...
n't I don't see how that works. And so it's a difficult thing to try to explain. But let me try to explain it with visuals, because I always use officials, All right, so we're going to simplify things here, and we have an object, a lands and a sensor As light travels from that little white spot through the lands onto our sensor. If our lenses in the right spot and L things are focused properly, we're going to get a white spot on our sensor that properly indicates what that object ISS now if we have the same lands and the same sensor, but we move our object closer and it's not properly focused. What happens is that it's designed to be focused at a different spot and our sensors not there and you'll notice on the sensor. We're getting this big cone of light, and what it is is it's a big blob of out of focus light, indicating that one spot that we were trying to sharply photograph. So if we can't move the lands or the object with a sensor, what we can do is we can force the light through a smaller aperture. When we force that aperture to be smaller at the lands, the cone of light on the sensor becomes a little bit smaller. And if we take this to extremes, we take those apertures and we force it down really, really small. The light hitting the sensor is going to be just about the same size is it would be if it was in focus and so we can force something that is out of focus to be pretty much in focus. In fact, this is the principle on which pinhole cameras work. They don't have any lenses. You poke a little pinhole in the camera. You let in a lot of light. Sometimes it takes hours of sunlight to get in there to get an image. And basically everything's in focus because it's coming through that really, really small opening. So it's easy to get in focus images through really small openings. But that's really challenging cause you're not letting much light into the camera. And so we're gonna have a little bit of a conflict as we get into letting in more light versus sharply focused light. All right, so reviewing we can open up the aperture to 1.4 to get shallow depth of field. We'll set it to 5.6 in this case for kind of a medium amount of depth of field, and we'll stop it down to the smallest opening on. This lends here 22 to get our maximum depth of field. And so we'll be making these adjustments depending on what we photographers want to have in our photograph. Do we want everything and focus? Or do we want to draw attention to one thing, have it and focus and nothing else and focus so depth of field is controlled by the aperture setting now, to make things really fun and exciting and complicated, it's also going to be affected by the focal length of the lands and the shooting distance. So there's actually three different things. They're going to throw you off in how much depth of field you're going to get. So as an example of depth of field controlled by focal length, if we look at a 50 millimeter lens at F eight, how much do we get in focus when we shoot this exact same subject? Yes, it looks a little different. But when we shoot the same subject from the same distance, we're going to get more depth of field with a 28 millimeter lands at F eight. And so, if we look at the photo on the left, pretty much everything is in sharp focus over on the right hand side. Some of the pigeons in the foreground are not in focus because with a 50 millimeter lands, we're not gonna get us much depth of field at F eight. And so what aperture you need to accomplish something will vary from lens to lens, depending on what you were doing. One general standard is true, and that is with wide lenses. You're gonna tend to get great depth of field, and with telephoto lenses, you're gonna tend to get shallow depth of field. Now you can kinda fight this and go upstream and try to get shallow depth of field with wide angle. And there's some things that you can barely do. And there's some things that you can do with telephoto lenses to stop them down to get everything in focus. But just on their own, wide angle lenses tend to give you lots of things and focus telephoto lenses air gonna tend to blur out backgrounds and things that are not right where you focused. It's also affected by how close you are to your subject. And so, in this case, I'm photographing subject from 32 and one feet away. And what I'll do is I will magnify all the results so that you can see them all equally. And you will notice here how shallow the depth of field is when you get down to one foot. And this is gonna be something that is hugely important to anyone who is interested in getting into macro photography. Depth of field is gonna be a major challenge for the rest of your life. If you're into macro photography. There's a few solutions out there, and we're gonna talk about some of those as we go through the different sections of this class. But when you shoot macro lenses, depth of field is a challenge. You're going to get shallow depth of field, even stopping down to 22. In some cases, you're going to get really shallow depth of field when you're using a macro lance so it's controlled by aperture settings, focal length and shooting distance, so kind of going back to some of the talk we had before about lenses. All right, we have equivalent focal length lenses. We've looked at this slide before these air all equivalent angles of view. They're the same aperture, but you're going to get different depth of field on them because they're using different lenses here, and so depends on the lens you have. It depends on the aperture you happen. So in this example, I am shooting with the equivalent angle of you. They're all at 1.4. But if you look on the left side of each of those photographs, the area that's out of focus, you'll notice that it's more out of focus with the 50 millimeter 1.4. And that is because of 50 millimeter lenses, amore telephoto lens and you're gonna get a shallower depth of field. If I stop that 50 millimeter lens down to F two, then it starts to be a little bit closer, and actually 2.8 now. All of these lenses are giving us a pretty similar depth of field. But I've had to change the aperture on these because they're different focal links because they're on different sensors. And so there's a lot of implications. You got this. So you end up with this, see, end up with that. And so, um, even though we're letting in the same amount of light, we're getting a different amount of depth of field because they're different lenses. Doing this again with a 302 101 50 lands. We've seen this before, but it's important to see, I think, shooting a subject. How out of focus is that background going to be? Even though you're shooting at 5.6 on these three different systems, you're going to get a shallower depth of field on the full frame. And it's not because you're shooting with a full frame camera. It's because your lands is of a longer focal length. That's what really matters. And so, in some ways, depth of field is not affected by sensor size, not directly. It's directly affected by the focal length of the Let's is actually on their If you want that shallow depth of field with a 4/3 sensor. Yep, just stick a 300 millimeter 56 lens on here and you'll get that shallow depth of field. You're going to get a different angle of view along with that. But depth of field is directly associated with Lance, not necessarily the sensor. And if you want to get more depth of field, we have to stop the 300 down to about 11 to make him look pretty similar to the 200 at F eight and the 1 at 5.6. And so these combinations right here they have the same aperture. So they have the same ability to work under low light conditions. If they had the same focal length, they would have the same depth of field. But because they have different focal links, they have different depth of field. Now imagine at this point in the class, there's some people who are getting a little confused, and they might be just saying, Okay, why don't you just give me a number? Tell me what number to send in my camera and I'll just leave it locked in there at the best aperture. Well, there is a little bit more to talk about, and I want to show you a photo, and I want you to help judge sharpness here. And so I want you to see what you think is the sharpest crops from this frame. And I'm gonna be showing you some crops from an image shot at 1.42856 11 in F 22 and you'll see a crop from the middle of the frame and the corner of the frame. And so let's see. I need somebody in the audience here to volunteers to what they think the sharpest aperture ISS. So let's get the microphone to somebody who would like to say what they think is the sharpest aperture who would like Toa volunteer an answer. What is the What is the sharpest aperture here to you? Like an eyesight test, but I think it's 11 for you. Okay, what would be the worst? 1.41 point four? Yeah, it looks pretty good, especially this one of the little lens down here. Now that looks bad, because lenses tend to be sharper in the middle and less sharp to the corners. It's difficult to make a perfect lands and lenses. All lenses are in perfect in some degree, and they tend to get worse as you get over to the corner, but at 1.4 this lens is supposed to be perfect. But if there is a flaw in the lands, you're going to see it pretty easily at 1.4. Now, when you stop the aperture down, it's gonna give you a little bit more depth of field. And it's going to disguise any sort of problems that that lens has. And when you stop it down to 28 and 56 and 11 it's going to continue to disguise and hide those problems that the lens might have in any imperfection that it has. But if you go too far, we're gonna end up with another problem called diffraction. And so, for the lenses that you own, think about the range that you have in the apertures. And if it goes from 1. to 22 the sharpest aperture is somewhere near the middle, maybe around 5.6. Now, if you have a lens that goes from F four down to, let's say F 32 the sharpest aperture is gonna b'more around the F mark. Now this does vary from lens to lens depends on a few other peculiar peculiar things. But in general it's the middle of the range and so you don't want to shoot it wide open. You don't want to shoot very closed. If you want the sharpness. The sharpest point on the lens. Now clarify. Just for a moment, the sharpest part of the lands is different than depth of field depth. The field is how much is in focus in front and behind the lands. I'm talking about just on a single plane. One object. How sharp isn't It varies according to what aperture? You shoot it out. So why are we going to choose a specific aperture? Well, there are technical reasons. We need to let in less light. So we stop the aperture down, we need to let in more light. So we're gonna open the aperture up. But sometimes it's for aesthetic reasons. We want to maximize the depth of field to have a lot in focus. We can maximize the sharpness like we just talked about there in the middle aperture range. Or we can go with shallow depth of field and really open up the aperture. And so those are the things that are going to motivate us. And as you can see, when we have kind of artistic and technical things on opposite sides of the spectrum, there's gonna be a battle. Are you technically need to do something, but artistically, you want to do something different, and so that's where we have to play around with a lot of the controls of the camera to get the effect that we want.