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Lesson 8 from: Choosing the Right Camera Lens

John Greengo

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Lesson Info

8. Aperture

Next Lesson: Equivalent Aperture

Lesson Info


All right. Next big thing about lenses that you need to know after focal length is the aperture. And the aperture range. And what it does. All right. So the aperture range on the lens is gonna allow you to control the light coming in. But it also controls the depth of field that you'll be able to shoot at. And so let's take our theoretical lens here that opens up to 1.4. And we're gonna get a very shallow depth of field. Those red lines indicate the front and the back edge of focus. And then we're gonna get in focus and out of focus area on our ruler. And so as we start changing our aperture we're gonna get a little bit more depth of field with each aperture change that we have. Now many lenses do not open up to 1.4 or 2 or 2.8. But in all cases as you close the aperture down you are going to get more depth of field. The smallest aperture on most lenses is gonna be around 22. But on some lenses it's 32 or 45. It varies from lens to lens. It's all generally the same concept though. The ...

wider the aperture, the less depth of field. The smaller the aperture, the greater depth of field. And so this is a good visual for you to remember. It's in the PDF that you get with the class. 1.4 is a big opening. 22 is a really small opening. As we go from 5.6 to f4, we're opening up. Or letting in twice as much light. As we go from 5.6 to f8, we're stopping down and we're letting in half as much light. So, for those of you at home, I have a little bit of a pop quiz for you. One question. We got three lenses here. These are Canons. Don't worry about what they, brand they are. But we have a 50 millimeter 1.2. A 1.4. And a 1.8. The questions is, if each of these lenses are set to f2.8, will they have the same exposure and depth of field? Now I don't think we're gonna have quite time to get all your answers in. But you can poop in if you wanna pop in with your answers. But think about that. Three photographers with these different lenses. They're all set to 2.8, are they gonna get the same exposure and the same depth of field? And, just for any of you who are trying to think a little too outside the box, you got the same shutter speed and the same ISO on your camera and you're pointed at the same thing. And so everything else is same. It's just that they just happen to have on three different lenses. Now I know this confused me in the beginning because I thought well, the one 1.2 lens lets in more light. Well it only lets in more light if you have it set to 1.2. When you have 'em, set to 2. it doesn't matter what the lens is, they're letting in the same amount of light. And so all three of these photographers are gonna have the same exposure and the same depth of field if they are shooting at 2.8. 'Cause that's our standard and that's the standard. 2.8 lets in a certain amount of light. Now, the 1.2 lens will allow you to let in more light than the others if you set it to 1.2. All right, let's talk about the maximum aperture on the lens. This is a, probably the second most important number when you look at buying a lens after the focal length. Now, some lenses will have a very fast aperture like 1.4. And it will be listed as one colon 1.4. Zoom lenses will often have two numbers. Like 3.5 to 5.6. The ones that I prefer, zoom lenses that is, are ones that have a single number. One colon four, which means the maximum aperture is f no matter where you zoom the lens to. With the lens on the right hand side of the screen the maximum aperture varies as you zoom it back and forth. Which enables that lens to be a little bit smaller and probably a little bit less in price. Now when you look at a lens like this that is a 50 millimeter one colon 1.4, what does that really mean? Well, the one colon is basically, it's a math problem. And the one represents the focal length of the lens. And so in this case, it's the focal length of the lens divided by 1.4. Now the focal length of this lens is a 50 millimeter lens. And so this is a math problem. You can bring out your calculators and run this little math problem, 50 divided by 1.4 is 35 millimeters. Now what is 35 millimeters? Is the opening of the lens. And this is not the front of the lens. But how much light, how big is the opening that light can get through this lens. And so it's got a 35 millimeter opening on the lens. And I'm telling you this just to kind of explain why some lenses cost more money and less money. And what's going on behind the scenes at the lenses. So we know our 50 millimeter lens has a 35 millimeter lens opening. And we'll represent that with this red circle on the right hand side of the screen. Now, 50 millimeter 1.8 is a very nice affordable lens that sells for less money. And the maximum opening is 28. A little bit smaller in size. That Canon 50 millimeter 1.2, one of the fastest 50 millimeters on the market right now, is gonna have a larger opening. And you can guess which ones are gonna cost more money. And which ones will cost less money. Let's compare it with some other different lenses. A 24 millimeter 1.4 is exactly the same speed. It lets in the same amount of light as the 50 1.4, but it doesn't need as big of opening because it is a wide angle lens. A telephoto lens on the other side can have a much, much bigger opening but still let in less light because of that magnification factor of that makes that a math problem that's much harder to do, you might say, when it comes to the physics of the optics and how they are made. Now the maximum aperture on prime lenses can range anywhere from 1.2 to 5.6. It'll vary according to what the lens does. And how big. And what they're trying to accomplish with that particular design. Zoom lenses will also have a maximum aperture. On some of the professional lenses, there'll be an aperture of 2.8 as the max aperture. Most common are these variable apertures, like 3.5 to 5.6 and so forth. And so there's a lot of lenses that fall into this category. This is probably the most efficient and easiest way to make lenses. One of my favorite series of lenses is the series of f4 lenses from the manufacturers. They have a maximum aperture that is constant so if you're setting manual exposure you can adjust your exposure and your zoom, but your, let me say that again, you can adjust your zoom, but your exposure stays exactly the same. Even if you're at the maximum aperture. A lot of the serious pros will shoot with 2.8, but I found the f4 is very good for travel photographers who are trying to save a little bit on weight and size. Now these zoom lenses that a 3.5 to 5. were the first two lenses that I ever owned were zoom lenses that had a maximum aperture in this range. And they were a good choice because they're versatile. They're not too much money. They're a great general purpose lens that can be used for a wide variety of things. And so I would use this for family photography, travel photography. They're not really highly specialized. They tend to be a little bit less money than everything else. And so they tend to be a very good value. And so they're a great price getting started. As you get into photography more and more and you start shooting manual more and more, you might find a consistent aperture for a zoom lens a little bit more convenient. And this is one of my favorite places in photography are the f4 lenses. And Sony has these. Olympus. And Panasonic. Canon. And Nikon. All have a collection of lenses with a maximum aperture of f4. They're definitely much more affordable than the lenses that go down to 2.8. They are lighter, smaller, and easier to carry around. And so I find 'em very good for travel photography which I tend to do a lot of. Wildlife photographers. It's also quite good 'cause they tend to be very mobile as well. And it's very good for landscape photography 'cause you very rarely need f2. when you're shooting landscapes. A lot of professional photographers rely on the lenses with a 2.8 aperture. And these are very important lenses for any system 'cause this is what a lot of the pros use. And the reason comes down to the fact is that they're shooting a lot of people for most cases. And people tend to move around a lot. And when people move around, you don't want 'em blurry so you need faster shutter speeds. And if you need faster shutter speeds, you need a lens that lets in a lot of light. And so these lenses tend to be really good for action, events, and people photography. Many years ago, I was working for a travel, a travel TV show, and I was traveling around the world. And I was photographing behind the scenes of the crew working in a variety of environments. And they asked me, John, what do you want to shoot this with? You can have any equipment you want. And I said, give me a 24 to 70 f2.8. I'm gonna be shooting people in a wide variety of settings. I can shoot portraits. I can shoot environmental portraits in group shots really easy and a fast aperture that lets me work in a wide variety of different lighting. If you wanna go faster than that, you're gonna need to go with a prime lens in most all cases. So there are lenses that will go down to f2, and 1.8, 1.4, and down to 1.2. And these are for people who are working under very low lighting conditions. Who are shooting action in the worst of conditions. And so if you were a concert photographer, or a sports photographer working in a dimly-lit gymnasium, this is where the 1.2 to 2.0 lenses would come in handy. If you are doing portraits and you want really shallow depth of field these lenses would be very handy. These are very highly specialized lenses. This would be the absolute wrong choice for a beginner in photography who's just wanting to learn their camera. These are very, very specialized tools. Now when I talk about these faster lenses you may hear a bit of reverence in my voice about these lenses because they are kind of a big deal. And you may be wondering, so what's the big deal with these lenses? Well, they are kind of extremes in the photography world. They allow us to use faster shutter speeds, lower ISOs, which means better image quality in a lot of cases. We can shoot under a wider variety of conditions as far as low light levels. For those of us who like to shoot shallow depth of field, this is where we get that really shallow depth of field look to things. For those of you with Canon and Nikon SLRs, we're also gonna be able to shoot with a brighter view finder. Which can be very handy. Now it's not a rule but in many cases you'll be able to focus faster. Because these are top of the line pieces of gear, they are gonna put their very fastest, most powerful, best motors in the lenses for focusing very, very quickly. And, while not always but usually is the case, these top end lenses are built better than other lenses. They have more metal in them. They have weather sealing. It varies from lens to lens. But it's just kind of a general attribute that you're gonna see on a lot of these high-end lenses. And so, they're fun to use. And I encourage you to rent one or try one out at some point. 'Cause they are really kind of working with lenses at their very best.

Class Materials

Bonus Materials with Purchase

Choosing The Right Camera Lens Handout (15 pages)

Ratings and Reviews

E.L. Bl/Du

John is one of the best instructors Ive watched. he's clear, concise, and gets right to the point. His display's and diagrams are so great, he makes very complicated subjects easy to understand, and fun. He holds your attention and interest b/c everything he says is valuable. This really helped me understand the vast complicated world of lenses. I would highly recommend this class to anyone who doesnt know what hyperfocal distance is.

Boris Dimitrov

Excellent class packed with incredibly useful knowledge. John is an amazing lecturer. He has also developed really great materials to help explain all the concepts and technologies that are explored in the class. Looking forward to my next class with him!

a Creativelive Student

Great class. So informative. John Greengo is such a fantastic tutor and explains everything in such and easy-to-understand way. I would highly recommend this class. Prior to doing this class, I was so confused about which lenses are best for various photography. Now I understand lenses completely. Thanks John!

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