Skip to main content

Lens Basics

Lesson 2 from: Choosing the Right Camera Lens

John Greengo

buy this class


Sale Ends Soon!

starting under


Unlock this classplus 2200+ more >

Lesson Info

2. Lens Basics

Next Lesson: Focal Length

Lesson Info

Lens Basics

So we're gonna get started with some lens basics. I know a lot of you know this, but it's time to review, to make sure everybody's on the same playing field. And we're gonna talk about some of those lens characteristics that are most important. So, interchangeable lenses. Well, the way I think about lenses, is that they are tools for solving a problem. And, like a handyman might have a tool chest with different tools in it. As a photographer, I want to have a camera bag that has different tools for solving different problems. Now, the downside is is that I can't carry all the lenses that I might want at any particular time. I can carry two, three, four, five, maybe six, but I gotta have the right ones in the bag at the right time. And the first choice that's gonna be made on any particular lens is the angle of view. What do you see from side to side in there. So we're gonna talk a lot about that in this first section. We'll be talking about the maximum aperture, how much light it lets ...

in, which also affects the depth of field. More topics that we'll be talking about in the first section. But there are a lot of other things that are very important in a lens. Obviously, image quality is important, and there's a lot of different things that go into image quality. So we're gonna talk a little bit about all these different factors that go into image quality. Is there anything else that's important in lenses? Absolutely. There's all sorts of physical characteristics about a lens. How big is it, how heavy is it. What type of filter? Does it use filters? Does it have a tripod ring on it? What's the price of it? There's all sorts of other things that are very important. And so, every lens is just a compromise. It does one set of things pretty well. But then when you switch to another lens, it may do something completely different, a little bit better, or a little bit worse. And so, you've got to find the right mix for your camera bag. The first thing to understand about lenses is that it is greatly affected by the camera you have, and most importantly, the sensor in the camera. There are many different types of cameras out on the market, we're going to be talking about four of the most popular types of interchangeable lens cameras. The largest of these common sizes is based off of 35 millimeter film. And this is what we would normally call, or now call, a full frame camera, meaning that it shoots the same size as 35 millimeter film. It's not actually the most popular type of camera out on the market. Kind of it's regulated to maybe about 10 or 20% of the field out there shooting right now on interchangeable lens cameras, because they are relatively expensive. Manufacturers have then made these smaller sensors to have smaller, more affordable cameras. The APS-C systems, which are two different slight systems between Nikon, Canon, and Sony in here as far as the sizes. And then, the micro four thirds system, which is a little bit smaller in size. So, the full frame measures 43 millimeters from corner to corner. I like measuring it like this, because then it makes the size really easy to determine how much bigger or smaller one is versus another. Now as I said, the largest of these common sizes is a full frame sensor, 43 millimeters corner to corner. And for those of you out there in the know, yes there are cameras with larger size sensors. Unfortunately we don't have time to get into those in this class. We're focusing on what is most popular out on the market today. So, Sony, Canon, and Nikon all have cameras that we're gonna be talking about, and lenses that are dedicated to this full frame system. The APS-C system, with the 28 millimeter sensor, is used by Fuji, Nikon, and Sony. And if you're wondering why does it say 1.5x? Well that is the crop factor, and that is the relationship of 28 millimeters to 43 millimeters. It's gonna make your images look 1.5 times more powerful in as far as the telephoto capabilities of it. And so we'll have a slightly different set of lenses that are appropriate for that camera than for the full frame camera. Canon has a slightly different size. It's a 1.6 crop factor. They can kinda be grouped together when we're talking about them because they are so close, but it is slightly different. And the micro four thirds has a two times crop factor because that sensor is roughly about a quarter the area but it's what we use to double the focal length to get the equivalent. So anytime you want to get an equivalent focal length, you're gonna need to go through this math. And if it's seeming a little bit complicated, that's understandable. It's quite normal and we're gonna go through and explain it in this class. All right, so if we take a normal lens on a full frame 43 millimeter sensor, light comes through the lens and it is projected on to the sensor. And it's projecting a circle because the lens is round. And that circle is big enough to cover the entire sensor area. Now, if you were to take that exact same lens and put it on a cropped frame camera, one that had a 1.6 crop for instance, well the light goes through the lens and does what it always does. It creates a large image circle. But the sensor in this case is a little bit smaller in size and so the image you get is known as a cropped image. It looks like a cropped version of the full frame sensor. And it's not necessarily bad. It's not necessarily good. It kinda depends on what you're doing. But it is something that you need to know because when we talk about the focal length of the lens, it's not the same thing as the angle of view. We need to know what type of sensor you have on your camera in addition to what type of lens you have on there. Now there are special lenses that are designed for these smaller sensors. They're less expensive. They're designed exclusively for that sensor so they tend to be very good for that. Nikon has these. They're called DX lenses. Canon has them. They're called EF-S. And Sony has them, DT or E lenses depending on which system you're using. Now if you were to take this lens and mount it or try to mount it on a full frame camera, well it doesn't project a large enough image circle on that sensor to cover the area so you get vignetting or darkening of the corners and you can't use all the pixels on your sensor. And so that doesn't work out too well. And it's something that generally, just people don't do. Because you're not really making full use of that sensor. So you can use lenses in some cases on both but not in other cases. So you need to know about your body, your sensor and your lenses to make sure that you have full compatibility. Now traditionally, the 50 millimeter lens has been known as the standard lens for a full frame camera. And what that's doing is it's giving you about a 40 degree angle of view, which is a very normal perspective. Now it's not the same as what you see with your own eyes, because we have two eyes and they move back and forth and they scan the horizon, but it is very similar to this perspective that we see the world on it. Now the crop frame sensor, the standard lens there is around a 35 millimeter lens. When you put a 35 on that crop frame camera, it's gonna give you about that same angle of view of around 40 degrees. So they're very, very similar. But if you peruse around the internet and you read about photographers and their recommendations of lenses, and you watch videos and you read books, you're gonna find that everybody's talking about the full frame sensor. And that is because the full frame sensor is based off of 35 millimeter film and that is kind of the gold standard you might say for photography. It's the way we talk about it and relate it. We just need one standard that we can all talk about rather than trying to adapt it and change it for 12 different sizes of sensors. And so that's kind of the standard that I'm gonna be talking about in this class. It's the size that people talk about when they record a video, or they write a blog post, or an article, or write a book about photography. And so if you don't have a full frame sensor, it's totally fine. But you are gonna have to kinda learn the translation of these numbers and I'm gonna help you out as we go through this class. So the focal length as I said is the most important feature about any particular lens. It's usually gonna be listed right on the lens pretty predominantly either on the top or on the front of it. We have a couple different types of lenses. We have fixed or prime lenses that have one angle of view and that's it. They just do one thing very very well. Or we have a zoom lens that can vary in its focal length. And can be very very versatile and handy in that regard. The other factor that's very important is the aperture, or how much light the lens is gonna let through. We have a couple different types of maximum apertures that are important to know about. With zoom lenses you can have a fixed maximum aperture like this of F4. More commonly though, you're gonna have a variable aperture like this one which is a 3.5 to 4.5. Which means the maximum amount of light that you can get in on the lens will vary as you zoom the lens from wide angle to telephoto. Or from one end to the other. On all cases, on all these lenses, you'll be able to change the aperture to a variety of settings, like F8, 11, 16, and 22, and so forth. And so we'll talk more about that in a moment. But that's just kind of a preview of where we're gonna be going with this information. Now, the other types of categories that we can talk about here are the zooms and primes. And a lot of people are always asking, especially those kind of new to photography is it better to have zooms or primes? And the answer is, it depends on what you're doing and what you want to try to get out of your photographs. The zoom lenses are incredibly versatile because you don't have to change the lenses. You have multiple focal lengths right at hand and you don't have to switch lenses to do it. The prime lenses are really nice because they're often a little bit sharper, they're faster, which means they let in more light, and they often focus a little bit quicker as well. And they tend to be smaller in size than the equivalent zoom lens for doing the same thing. What I have found in general is that it's good to start with zooms. And then as you figure out exactly what you're doing, where you want to do something particularly well in one area, then you start getting prime lenses. I know I started off with two basic zooms. I had a 3570. This is back in the film days. 3570 basic zoom and a 70 to 210 zoom. And then as I started realizing some of the things I wanted to do, I started adding in a particular wide angle lens and then a 85 millimeter portrait lens. And some other lenses in there. And so as you get to learn, oh, I'm trying to shoot this particular type of sporting event, or I want to shoot portraits, or I want to shoot landscapes in a certain way, then you may want to get a prime lens when you really want to do that. They're also very good when you get to low light. But we'll talk more about that when we get to the section on apertures.

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!

Student Work