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Focal Length

Lesson 8 from: FAST CLASS: Fundamentals of Photography

John Greengo

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Lesson Info

8. Focal Length


Class Trailer

Photographic Characteristics


Camera Types


Shutter System


Shutter Speed Basics


Camera Settings Overview


Camera Settings - Details


Sensor Size: Basics


Focal Length


Lesson Info

Focal Length

we're gonna be getting into one of my favorite aspects of this whole class and that is dealing with the lands and so obviously very critical factor. And with are interchangeable lenses. When you change the lens, you're basically changing the camera. You have a whole new camera to work with. So let's get in and talk about the lens. Have a lot of things to talk about in here, and a lot of important sections will start with focal length, and then we'll get into the depth of field parts later on. And we do have lots of quizzes for you. Out there were gonna be in studio audience. We're gonna be awarding a lot of points today, so there's gonna be a big change in the point board here today, I think. But it's a good chance for all of you at home to really test to see if you've really learned what we're teaching in this class. All right, let's get started on the focal length Now with lenses, there are some primary characteristics when I am purchasing or choosing a lens to use. Generally, number...

one is the angle of view. What am I going to see from side to side. That's that's the main reason we're choosing one lens over the other. But we're also choosing a lens for its light gathering ability. If we work under low light conditions, we're gonna need a particular type of lens. And with that aperture, the light gathering ability, it's also going to determine how much depth of field we can get from the lands. And so that is the main reason we're gonna buy one lens or choose another lens for a particular purpose. But there is a lot of other things to consider, and I don't know that I would base a lens purchase on it. But it's something I would want to be aware of, and these go into the secondary characteristics. The first of these is image quality. That's right. Image quality is actually a secondary consideration on many lenses from most people. Ah, but there's a lot of different things that go into image quality. It's not just simply a number or one attributes, and we're gonna take a look at all the different little things that go into image quality. Beyond that, there's a lot of physical things, the size and the weight of the lens. Does it use filters? What types of filters? All sorts of other things that are going to separate an inexpensive lands from a very expensive lens. And we're going to go through a lot of these to talk about what's important and what to pay attention on on these lenses. So when you take a look at a lens lens on your camera, perhaps it's gonna have to really important numbers. Number one is the focal length. As an example, it might be in 18 to 55 where it might be a 50 millimeter lands, and the other really important number is the maximum aperture. This is how much light it can let in at its maximum opening. And that's really a standard for how good that lenses under low light conditions and how versatile it could be for a variety of types of reasons. And so we're gonna talk about both of these, but we're going to separate him and talk about one, and then we'll talk about the other, and then we'll get it all together and talk about both of them eventually. So first off, focal length, it's the distance from the nodal point to the image plane, and we don't have to. We're not gonna get too deep into the technical talk here. It's basically from the front of the lens to the back of the lens, and there's a little bit of play on that. It's not exactly that, but it's pretty close to that. And that's why a 50 millimeter lands is relatively small, and a 400 millimeter lands is relatively big. Is that because that nodal point is out there further now? We can't go very far in talking about lenses without refreshing a little bit about what we talked about on sensor size in the previous class. And that is because focal length and angle of you are very much related to censor size. And so let me take you through another illustration to show it to you in a slightly different way if we have a lands and it really doesn't matter what lens it is, But any lands lights gonna come through that lens and an image is gonna be projected onto that sensor. The round image has just enough area to cover that sensor area, and that's how we get our image. We can take a copy of that lands that exact same lands, and we can put it on a camera that has a smaller size sensor. What happens? We'll light goes the lens, and nothing changes about that. It produces the same size image circle. It's just that we have a smaller sensor in there, and so it's grabbing a slightly different, narrower angle of view. It's kind of the same picture, but not quite. It's not exactly the same, and so we have the exact same lands. But we have a different sensor, and a different result from that. And so Focal Inc is not the same thing is angle of view. It might have been better if we had decided in the photographic world to just call lenses by what angle of view you see from them. But that would vary according to what camera you put them on because they have different size sensors. And so it gets a little complicated because there's different factors involved here now. There are many companies like Nikon, Canon and Sony that make lenses that are specifically designed for the smaller frame sensors. And sometimes those lenses are a little bit less money because they're a little bit simpler to design because they don't have to design as big of image circle on it and they have special names. Cannon calls him E F s. Nikon calls them DX and so forth. Now, in some cases, your ableto take those lenses and put them on to a full frame camera. It doesn't turn out too well because they don't produce a large enough image circle to cover the corners and Nikon. You can put the smaller frame lenses on the full frame body, and I will allow you to shoot, and in some cases it will automatically just crop in if you want, so that you don't see those vignette ing dark corners. Now, if you have a 24 megapixel camera, that's going to reduce you down to maybe 14 or 16 megapixels, so there's kind of not really a good thing to Dio, Cannon said. You know, this is just a bad idea. They produced a different mount so that you can't even mount those lenses onto the full frame canon cameras, and so you can technically do it in some cases. But I wouldn't recommend it because you're not getting really good quality results from it. For a long time, the 50 Millimeter Lands has held kind of a special notable place for photographers, cause it's the normal lands. And a lot of times I remember when my dad bought a camera he was looking around to see which 50 millimeter lands he could gets. He wanted get the fastest one for the money on. That's what cameras came with 50 millimeter lenses. They were small, practical and not too expensive. So when you put a 50 millimeter lands on a full frame camera, you're going to get what's considered a normal angle of view. And that's not to say that it's the same angle of view you see with your eyes. But as far as the perspective of size relationship of objects you're pointed at, its normal. It's about 40 degrees from side to side. If we take that same 50 millimeter lens and we put it on one of our 1.5 crop cameras, which there's a lot of them out there, they're going to get us a little bit narrower angle of view of 27 degrees. If you have a 4/3 camera, you put a 50 millimeter lens on that, you're gonna get yourself a 20 degree angle of view. And so that is simply because we have smaller size sensors but the same size lens going back and forth. So nowadays the normal lands is still the 50 but on the crop frame it's around 2 35 And for the micro 4/3 system, it's gonna be about a 25 millimeter lands. And what I have to admit is very unfair in the modern world. And I don't like things that are unfair. And that is, is the fact that the gold standard for what we're gonna talk about in this class as well as everyone else out there is based on full frame cameras. And I have, ah question for our audience here. Just raise your hand. Who owns a full frame camera? Raise your hand up. Okay, so we got 123 We got four out of about 16 people, so 1/4 of our audience owns full frame cameras. You guys are in the minority, Alright, they cannot vote you. They could just start saying that this crop frame camera, who has about a 1.5 crop frame camera. Okay, that's many more. That's almost the other half of the double, about eight of them there. So far more people in my classes and far more people out shooting photos with these interchangeable lens cameras have about a 1.5 crop frame sensor in their camera. That's the most common, but 35 millimeter film was the most common. And that's why when photographers like myself or someone who writes a book or postal blawg or make a video and they talk about angle of view and lenses there almost always talking about full frame gear, it's also what a lot of professionals use who write those books and make those videos and write those blog's and so forth. And so that's kind of the standard. And so it's The onus is on you to kind of do that math to figure out OK, he's talking about that. But I have this and you're gonna have to do that little math yourself. All right, so these are what we call equivalent focal length. They're going to give you equivalent angles of view. So if we have three photographers with these three systems and three different lenses. They're gonna be taking basically the same photo when it comes to angle of view. And so that's gonna be with a wide angle lens. You want a decent wide angle lens, you might need a 28. You might need a 17 or you might need a 14 depending on which system you're using. And so you always have to be relating things back to what's relevant to you with the system that you use. If you're looking for a pretty good telephoto lens, it might be a 300 or 200 or just 150. All of these are going to see about the same angle of view. Now there are two major categories of lenses. We have prime lenses and zoom lenses, so prime 50 millimeter is your normal lands. And then, as we get to lower numbers, we have wide angle lenses like a 35 and then eventually we start calling them ultra wides at about 20 millimeters tele photos. And then once we get to 400 we throw the super in there. They get to call him Super Tele photos at this point, and there are a lot of zoom lenses because they are very practical and easy to use in a lot of cases. And they're gonna run range the full gamut from ultra wide to super telephoto as well. Now a lot of people are always questioning well, should I get a zoom lands or should I get a prime lens? What's best? Well, they both have their place in their purpose. I see zooms as incredibly versatile. You don't have changed lenses. You have all the intermediate focal links on them when you're not totally sure about what you're going to be doing. And that's okay to be not sure about what you're doing every time I go traveling, I don't know what I'm going to be doing that day. That's the whole fun of traveling this. It's gonna be something new. I could be shooting a portrait or a landscape or our good agricultural shot or an architectural side. You don't know what you're gonna be doing this, so zoom lenses are very, very practical. But when you really do know what you're doing, you're going to be going to the basketball game. You're gonna be shooting a portrait in your studio or at the park, and you know exactly the type of result that you want to get and you have some control over the situation. That's when the prime lenses really get to be very, very handy. They're also really good when you just know that you want to simplify things. There's a lot of times I've been walking the streets of some foreign city and just have a 50 millimeter lens on and my brain just starts. OK, I'm not going to think about what I can or can't shoot with a 15 millimetre lens where 400 my brain just starts focusing in on. What can I do with what I have? And it's It's a fun way to narrow yourself down. Just say, Let's do this one thing. Let's do it right And it's just good practice for photographers to limit themselves in that way.

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