Aperture: Quality of Light & Depth of Field
Moving on to aperture. If we come back to our eyes, and comparing them to a camera, what part of our eyes do you think would be like the aperture? The aperture controls the quantity of light that's allowed to enter into the camera, or into our retinas. Anybody, microphone? (laughs)
The iris, or the pupil.
The pupil, that's right! Okay, so what happens when you are in a really dark room, what do your pupils do? (imitates whooshing) They dialate, right? So they can let in more light so you can see better. And then if you flip the light on suddenly, your pupils constrict, right? Because, oh my gosh, light bright, light bright, right? Like Gremlins? (laughs) I'm not the only person who remembers that movie, right? Okay, yeah, so your pupil's gonna dialate or constrict, and you can actually see this happen if you go, like, stand in the bathroom with the lights off, and let your eyes adjust for minute, and then flip the lights on and look in the mirror, and you'll see your pupils go shoo...
p. It's kinda neat. So that's what your aperture does. It controls how much light is allowed to come through the lens or not. And it is actually a function of your lens. So that means that if I take this lens off my camera, and put a different lens on, the other lens, whatever I put on here, may have different aperture capabilities than this lens. That make sense? So it's not built into the camera the way the shutter speed is, it's built into your lens. So if you can change your lenses, your aperture possibilities will also potentially change. If you have a point and shoot, then it's built in, because it's all in one, so that's sometimes even easier. So let's talk about this. Your aperture then can range from being what we would call wide open, something like this, and it's actually built of little blades that swirl open or swirl shut. So something like this, that's my depiction. (laughs) So we have wide open, and then on the other end of the spectrum we have nearly closed, so just really like a little pinhole, like you might find on an oatmeal box camera, if you ever made a pinhole camera. Alright, and then, of course we have all kinds of things in between. We have more than what I'm showing you here, this is just for purely illustration purposes. In fact, you would have something along these lines. And actually, again, more than what I'm showing you here. But on one end of the spectrum we would have a wide open aperture, and then all the way across it would be quite narrow. And they have different effects on our images. A wider aperture is gonna let in more light and it has the effect of reducing our depth of field. Or, here I wrote depth of focus. If this is new to you, maybe that helps you understand it a little better if we call it depth of focus. So a shallow depth of focus is gonna give you a blurry background and a blurry foreground. So wherever your subject is that you focused on, as objects in your scene get further away from your subject they're going to become blurry. On the other end of the spectrum when you shoot with a narrower aperture, your field of focus gets deeper, so that's often used in landscape photography when you want a deep range of focus. Whereas the wider apertures would be used more often in portrait photography, for example. Apertures are also fractions. We call them F stops, so F stops are ways of measuring light. So if you think about when you bake a cake and you measure sugar by the cup, or the half cup or whatever, in photography we measure light. Instead of cups full of light we call them F stops. So we have F stops of light, and they are fractions, so for example we have F over 2.8, we would call that F 2.8. I'm at F 2.8, or I'm gonna shoot at F 11 or whatever. So those are called F stops, and they are our aperture settings. And what's kind of mind warpy is that the smaller numbers like 2.8 is actually a wider opening than, for example, F 16 is a squinty little opening. So to help you remember that, you wanna keep in mind that these are fractions. And if we were talking about pizza, what is it with me and food? (audience laughing) Cake, pizza, I don't know. If we were talking about pizza and I was like, hey, would you like one fourth of the pizza or would you like one sixteenth of the pizza, which one would give you a bigger slice? The fourth, right? So just keep that in mind when you're thinking about-- Ooh, what was that? When you're thinking about these numbers keep that in mind so that you can easily work out that F 2.8 is a wider opening than F 16. And then when you're like, "oh, which one made the blurry "backgrounds and which one didn't?" The wider apertures are gonna make that blurrier background, and here's my trick for helping you remember that, I don't know if this is scientifically accurate, but I'm gonna go with it. When you're driving down the highway, for example and you're trying to read the sign in the distance, that's pretty far away, what do you tend to do with your eyes to try to focus and see that sign? You squint, right? Like, oh let me just, and you turn down the radio, because goodness knows that helps. Turn down the radio and then squint, and suddenly you can read things. We squint when we're trying to see things that are far away, and I don't know how that's related, but I'm gonna just say that it is 'cause it makes sense in a way, sort of. So the squintier, the tinier, that that aperture is the deeper you can focus within, the deeper your range of focus within your scene. So let's look at some examples, because that helps. (laughs) So here's my cutie little boy. He's in everything now, sorry can't help it,. He's around when I'm creating these materials, so he gets pulled into stuff. Okay, so yeah, so cute. So this was captured at, I don't remember what. Some aperture. Would you say this is captured with a wide aperture or a narrow aperture? Wide, right? We know that it was captured with a wide aperture because we see this deliciously blurry background, and this deliciously blurry foreground. So my focus was on him when I was doing this, and then anything in front of him or anything behind him becomes progressively more blurred. And that's because I shot it with a wide aperture. Now, here's the same scene with a squintier aperture. I think this was like F 22 or something. So now we can see all of these plants, and the plants back here, so that's how that works. Here's another example. When I shoot wedding rings and such for my wedding clients, I tend to shoot them with a macro lens and a very, well, relatively wide open aperture. And it creates an effect where the front of the rings, like the stone and the prongs that hold it in place, are in focus and then even if you look on her ring over here, the diamonds actually become blurred, because they're falling away from the camera. And if this comes across on the monitor, you can actually see a strip here. I think I probably shot this on a table cloth or a napkin or something. It's got a bit of a texture, you can actually see a little strip. I mean, it's a narrow, actually I have it highlighted in this next frame. (laughs) Thank you for keynote, that's so helpful. So it's actually this just little strip of focus that runs across the frame, so anything in front of that strip or anything behind it would be blurred. And your aperture basically controls how wide that strip is, right? So it's like also if you were taking a group photo, let's say you were at a wedding and you're shooting the whole wedding party, let's say they're somehow five rows deep, would you want a wider aperture or a squintier aperture to make sure that your front row and your fifth row were still in focus? Squinty, right? Because that's a pretty deep range to get all in focus, so you'd wanna squint that aperture down to widen that field of focus. Hopefully this is sinking in. Yes, okay. So, now we go back to the camera, how do you control all this stuff? Again, it's gonna vary model by model, but for example on my camera I have this dial right here. This controls my aperture. So this controls my shutter speed, this one lets me change my aperture. I can see what my settings are on my display up here. Again, it's not gonna say, probably, I mean it varies by manufacturer. But it will probably not say F 4, it might, mine just says 4, or 4.0, or whatever. So you have to kind of get familiar with your camera. You'll also see that, of course, when you look through the screen. If you have a DSLR, a different model of DSLR, sometimes you don't have that dial back here, so what you would do in most cases, is you'll have a button, it says AV and it has a little plus, minus. If you press and hold that button, and then spin your, the same dial you use to control your shutter speed, it will magically now control your aperture. So you just hold that button down and then spin that dial, and it will control your aperture. And, again, on the point an shoots, they're all different, but the ones that I've worked with, there's a ring around the lens in the front. And that's how it was on my old film camera. You controlled the aperture by spinning this ring around your lens, so it's kind of fun to see that on a digital camera too. So that's how it works on point and shoots, sometimes. So when it doubt check your manual, because who knows what the camera manufacturers do, but that's generally how it works and what you're looking for. So again, folks at home, figure out where your aperture control is, and then just spin it around to see what your options are. That's again gonna vary depending on the lens that you have. So just see how wide you can go, and see how squinty you can go, just so you know what you're working with.