All right. We've been talking about lenses, but we're gonna continue talking about them because now we're gonna be talking about the aperture in the lens. And so, that's where we're going to be determining how much light is coming in through the lens. So, aperture is the opening through which light travels. And this is a term that gets misused quite a bit in the world of photography. And, so when you hear someone talk about aperture, that's not always exactly what they're talking about. On the front of your lens, on the top of your lens is something that is labeled, like 1:1.4, and this is maximum aperture. This is the most amount of light that that lens will let in. And some people will mistakenly say that's the aperture. "Oh, that's a nice lens. What aperture is it?" No. What's the maximum aperture? Because it has several apertures it can open or close to. This is also what we, kind of, generally refer to as the lens speed. And the 1 and the colon basically indicates that it's actual...
ly a fraction, but they only have one line to work with, and so that's how we know the key number is 1.4. Now, in the lens itself, is a mechanical device that opens and closes, and that's the aperture unit yourself. Virtually all cameras are going to have an aperture in that lens like that. And that's also what refer to as our f-stop, as well. So, the f-stop. The ratio of the focal length of the lens to the entrance pupil. Okay. It's a really fancy way of saying the size of the opening in the lens. And so, this is the graphic you should memorize, for all you photographic memory people, as far as, what is 1.4, it's a very large opening. What is f/22? It's a very small opening. And this is where most people who are new to photography make a lot of mistakes, because the small number, 1.4 is a big opening and the big number, 22, is a small opening. Because they're fractions, things are reversed. And so, this is something you'll get used to, just keep practicing and keep this visual in your mind, as far as, what's 1.4 versus what's f/22? So, in our lenses, as we stop our aperture down, the aperture blades close in to create a smaller size opening. With each smaller size opening, it lets in half as much light. When we open it up, it's letting in twice as much light with each one of these settings. And, there's gonna be a smallest number, there's going to be a biggest number. And so, we can use this as an additional way after shutter speeds and after ISOs, to control the amount of light. Now, if we have aperture 5.6 selected and we open up to f/4, we are opening up a full stop of light and we're letting in twice as much light. If we go down to f/8, we're stopping down, we're letting in half as much light, and this is different than shutter speeds or ISOs. Because back in shutter speeds and ISOs, we doubled the numbers, remember that? We cut the numbers in half, we cut the light in half. But in here, when we go to 5.6, we're not doubling the number, we're going up by this small little fractional amount there, but these are, kind of, core numbers that indicate these whole f-stops, and so it's a little different numbering range, and it's fairly easy to remember these numberings, if you remember that you start at 1 and then you go to 1.4. If you can remember those two, every other number is larger than the previous. And so, if you want to go 5.6, you want to go up, well you could f/4 times two is f/8, and then 5.6 to f/11. So, it's just a series of numbers, and I'm afraid to say, you're gonna have to memorize these. It's not that hard if you can remember 1 and 1.4.