Exposure Triangle: Aperture
All right, let's talk about aperture. If we think again of our cameras like our eyes, what part of our eyes would be like aperture? Aperture is the opening in the lens, I'll define it for you first, is the opening in the lens, that allows light, it controls the quantity of light that comes in. So it can dilate to let more light in, or it can constrict to reduce the amount of light that's coming in. So what part of our eye might that be like, Gabby. I feel like you know this. You know this.
Okay, would it be like your pupil?
Yes, exactly. It is like your pupil, all right. So if you've ever gone to the eye doctor and had your pupil dilated and they get really big, and then you have to wear sunglasses because all this light is coming in and it's too much, that's exactly how aperture works. It's different than shutter speed, because your shutter speed is built into the camera, right, it's part of the camera body. Aperture is a function of your lens. So depending on the lens that you ha...
ve on your camera, your aperture options may change. But it controls two things then, it controls the quantity of light, as I mentioned, like your pupil it can dilate or constrict, and it has this other funny little side effect that it controls something called depth of field. And we'll see what that means in a minute, but that basically controls how deep into the scene you can focus, you can have focus, okay. We'll see that in a minute. But here is what the aperture might look like in your lens, its a series of little blades, and it can swirl closed, or they can swirl open. So they can range from being really open, what we would call wide open, and on the other end of the spectrum, it's nearly closed. So not very much light getting through, and of course, there are several stages in between, again, more than just four, but you kind of get the idea here, so when we look at this, we have wide-open aperture, on one side, and on the other side, we have a much narrower aperture, so more light is coming in on the wider side, less light is coming in on this narrower side here on the right, and that the size of that opening is also measured as a fraction, it's called, we refer to it as an f-stop. We measure light in f-stops, exposure is measured in f-stops, kind of like sugar, if you're baking cookies, you might have sugar by the cup, in photography we have light by the f-stop. So, here a wider opening would actually have a smaller number, like f/2.8, for example, that's how we would say that, we would say, my aperture was set to f/2.8. For example. That would be a wider opening, than, for example, f/16. F/16, even though it's a higher number, it's a tinier opening, okay. You can think about because they are fractions, it's the same like if you ate pizza, if you had 1/4th of a pizza, like f/4, that would be bigger slices than if you ate 1/16th of a pizza, you'd be getting less. So it's the same idea, it's a fraction, and the result that this has on our images of course, is there's more light on this side, less light over here, but it also controls that depth of focus or depth of field, it's called. So, it turns out, that with a wider opening like on the left, you have a shallower depth of field, so I'll show you an example, and on the narrower side, you have a deeper depth of field. So let me explain what that is, and then I'll give you a trick for how you can remember. Cause I remember when I was learning photography, I was like, oh, I do not get all this. Numbers and like, they look like pies to me or something, and I was like, I'll figure it out later. And I did, thankfully, but it doesn't have to be that hard. So, here's an example. So here's a little scene, where we see these little toys, and we can see all of them, the squirrel is in front of the tree, which is in front of the bear, which is in front of that orange thing, which is a chair, which is in front of the bookcase, and we can make out all the objects, some are sharper slightly than others, but we can see them all and make out what they are. This was shot at f/16, so the tiny little opening. Okay, the same scene was now photographed with a much wider opening, and now we see the bear is sharp, and everything in front of, or behind the bear, is not sharp. And it gets progressively less sharp as it moves away from the bear. So the bear was my focus point, and so, aperture controls how much distance surrounding the bear, is going to be in focus. How much distance in front of, and behind the bear is in focus, that area is called our depth of field. And aperture can give us a deep depth of field, or a shallow depth of field. Here's another way to look at it. Here are wedding rings, this was shot on a macro lens, which makes for a really skinny, shallow depth of field, and it's hard to tell, I have it depicted here in the next slide, but you can see, if you look very carefully, so that the prongs on the stone are in focus, right. But the back of the ring is blurry already. That is a very shallow depth of field. The front of the ring is in focus, the back is already so blurred we don't even really see it. We can see that the portion, this was shot on a napkin, I think, we can see that the portion of the napkin, down here below, that is at the same distance from the camera, as the front of the ring, you can see a perfect line, where it's in focus. And anything in front of or behind that, gets blurred. Here's another example, here's a flower, shot from above, so we can see this area of the flower on the left that's protruding up closer towards the lens is blurred. The middle petal here is in focus, so that's what I focused on, and the petals behind it, are also blurred. So that's a pretty shallow range of focus, shallow depth of field, one more example, actually we have a couple more, this is a glass full of straws that I shot at a wedding, you know, you have to capture the details, and I love this, for some reason. But, I love, again I shot it from up above, so the tops of the straws are in focus, and as the straws get down further away from the camera, they become blurry. So, this is commonly used in portrait photography, so here's an example of, this is my son Zay, this was the first day that he got his glasses, I thought, we have to go take some pictures. So, I got this photo of him, this was captured at f/2.8, so fairly wide, and that is why the background is just an indiscernible mess of color. We have a question from Jose.
Yes, you said aperture is part of the lens, so is there different focal lengths, or depth of field, per lens?
Yes. So, great question, and we'll cover that in more detail when we talk about lenses, but, to answer your question just quickly now, yes, so some lenses are able to open their aperture wider than others. So, I can get this very yummy blur on this particular lens, but with another lens, it might not be quite so blurry, because that aperture can maybe only open to f/4, or f/5, depending on the lens, and the focal length. So, great question. Yeah, that's why it starts paying off to really learn about lenses and what they're capable of, and we will definitely be talking more about that. Here is an example of landscape. A landscape situation, where you would want a deeper depth of field, right, so if we go back here, he's in focus, behind him is not, that's great for portraits, oftentimes, but in a landscape situation, you probably want more, a deeper area in focus, so here we see these boats up front are in focus, as are the second row of boats, and the buildings in the background, et cetera. So this is a deeper range, and this would be used, still, even with portraits, if you were taking group portraits, maybe you've got five rows deep of people, you're gonna be in trouble if you're trying to shoot them like this. The front row will look good, and the back row is not gonna be recognizable, right. So you do have to pay attention to your aperture, and what effect it might be having on your depth of field, so that you can get things the way that you wanna have them. So where do we find aperture on our camera, and how do we control that? Again, in this example, I'm gonna suggest that you dial on over to manual mode, and then, on your camera, there is, it depends on your camera model, some cameras, like the one that I shoot with, the aperture's controlled with this dial on the back. So, completely separate button, or separate control, that's gonna let me control my aperture, not all camera have that, so don't worry, I'm not leaving you hanging, I could see on my little display here, this was currently showing an aperture of f/4, now if you have a Canon Rebel, or something along that series, or whatever, a Nikon kind of equivalent, then what you probably gonna have is, a little button that you see circled right here. Somewhere on your camera you'll have something that'll say, a little button on the back like this says, Av. And what you'll do is hold that button down, while you turn the same dial that just moments ago controlled your shutter, if you hold that button down while you turn that same wheel, it will now control your aperture, in manual mode. So that's how that works. And on my point-and-shoot, I had a ring actually around the front of the lens. I thought I had a slide of it, but apparently, I cut it somewhere. But there's a ring around the lens that you would turn, that would control the aperture, so. It really just depends on your camera, but that's where you wanna look for those things. So, here's my little trick to help you understand the depth of field situation, and which kind of setting does what, the wider openings again, give you a shallower field, resulting in those blurred backgrounds, and foreground, too, if you have foreground in your photo. So the wider openings is a blurred background, the narrower openings give you more depths, that's in focus, the way I remember this, is if you again think about it like your eyes, what do you do when you're driving down the highway and you see a sign in the distance, and you can't quite read it. What do we do with your eyes? We squint, right? I don't know if this is scientifically accurate, I'm kind of just, making this up, but it works for the analogy, so I'm gonna go with it, but we squint, I don't know what that does biologically to help us or not, if it's all in our heads or whatever, but we do it. So we squint, almost like we're trying, like that's gonna help us read better, that sign that's far away. So, we're squinting like this narrower sort of opening. So I think of those narrower openings, I call them squinty apertures. So the squinty aperture, is gonna give you a deeper focal range within your image, within the scene, right. Whereas the wider ones are gonna result in the blur, that's in front of and behind whatever you're focusing on. How blurred will depend on a number of things, your lens, your distance to your subject, as well as your focal length, but, that is how you get the blur.