Lens Considerations: Maximum Aperture
Okay, so back to our lens considerations. We talked about focal length, measured in millimeters, wide or telephoto, the lenses can be zoom or prime lenses. The other thing that you really wanna consider is the maximum aperture, if this matters to you, if you want, like I like, to be able to shoot with a wide-open aperture, then you really wanna look at what the lens maximum aperture is. So just to refresh your memory, back to the very first lesson when we talked about exposure and we talked about shutter speed, aperture, and ISO, aperture is the opening in your lens that, like your pupil, can either dilate to let in more light or it can constrict to reduce the light that comes in through the lens. So the range of settings that's available to you will vary, pretty dramatically, based on your lens, or the lens that's built in, if it's a point and shoot. So for example, my favorite lens that I currently have and shoot with is a 50 millimeter prime lens. The maximum aperture on it is f/1.2...
, that's really wide. That's a very wide lens, or wide aperture. So we call that a fast, fast glass. That's a fast lens. And I'm guessing here but I'm gonna say, I think I'm pretty right-on here, but I'm just guessing, just in case someone's at home going, no you're wrong! I am assuming that we call that fast glass because, by having such a wide maximum aperture, it allows us to use a faster shutter speed. So if you're in a low-light situation and you don't wanna reach for a tripod, having fast glass means you can open the aperture wide enough that you can keep the shutter speed at a level, hopefully, combined with ISO, where you don't have to reach for a tripod. I don't know, that's my theory. I never actually Googled why we call it fast glass. Maybe someone knows, but I'm assuming that's why. So we call those lenses with wide apertures fast lenses. So this lens has a max aperture of 1.2, f/1.2. My zoom lens that is 70 to 200 has a max aperture of 2.8, so not as wide, but still, 2.8's pretty wide. Other lenses have an aperture with a max aperture that is a range. Oh, so, look at that. This one has a maximum of f/ or to somewhere between 3 and 5.6, what does that mean? First of all, this stuff is all printed on the front of your lens somewhere. So when you're shopping online, it'll be obviously in the item description or the name of the lens. If you're at home, going, what is my lens, I have no idea, just take the lens cap off and look. Point the camera at your face and look on the front of the lens, and it'll tell you your focal length and the maximum aperture. So for most people who are at home following along, if you have a DSLR that came with a kit lens, it's probably a lens like this. This is an 18 to 55 millimeter lens, and the maximum aperture will range somewhere between f/3 and f/5.6, depending on how zoomed in or out you are, so where you are within the available focal range actually will influence how wide you are able to open your aperture. That's why this is a range of numbers, whereas on these lenses, it's just a set number, 2.8 or 1.2, there's no range, over here, this one has a range, okay? So that means if you're zoomed all the way out, you can open the aperture to f/3. And even if you don't touch your camera settings but now you zoom in, the aperture will automatically shift from 3 to 5.6, just because the optics are such in that lens that that's the way it works, okay? But these are very good general-purpose lenses. They're much less expensive and they cover a pretty good range, like 18 to 55 millimeter. So they're very popular as a starter lens or a lens that comes with, you know, your camera in a kit like that. Okay, but that's what that means. So how does this really affect this whole exposure situation? Well, as I just mentioned, if you're in a situation where you don't have enough light, so maybe you're, let's just pretend you're in manual mode for the sake of understanding this, but you may not have enough light, since it's dark, you're getting a dark exposure. And let's say you've already maxed out your shutter speed and your ISO, if you have a lens that has a wide aperture, you could really open up that aperture and get the exposure that you need. I mean, in theory. So it gives you, it lets you have more options. So for example, I shot a wedding a while back that was lit, the ceremony was lit entirely by candlelight. That was a really dark ceremony, I mean, it was really dark, yeah, and I was freaking out, because I'd never shot something like that before, and I was like, oh man, I hope, you know, I have fast enough glass. And it worked out, but like barely, and only because I also jacked my ISO. I mean, it was really dark in there. So I had my aperture as wide as I could get it, my shutter speed as slow as it can go without needing a tripod, and my ISO was as high as it could be, so I could squeeze every drop of light out of that scene, to get away with my pictures and not have to pull a tripod out. So it worked, whew, so I was really grateful. But if I had had a lens with less capabilities for the aperture, then I don't know, I guess I'd be shooting RAW and not getting (mumbles while laughing) and try to have a bit more of a buffer in that situation, so it can be really helpful.