Skip to main content

Lens Speed

Lesson 10 from: FAST CLASS: Fundamentals of Photography

John Greengo

buy this class


Sale Ends Soon!

starting under


Unlock this classplus 2200+ more >

Lesson Info

10. Lens Speed

Next Lesson: Aperture


Class Trailer

Photographic Characteristics


Camera Types


Shutter System


Shutter Speed Basics


Camera Settings Overview


Camera Settings - Details


Sensor Size: Basics


Focal Length


Lesson Info

Lens Speed

So the next section here is dealing with lens speed, the maximum aperture of the lens. We were dealing with the angle of view, and now we're starting to talk about how much light the lens let's in. And so this is a very important factor is one of the most important things that I want to know about in a lens that I am choosing to buy or use. And so that is the maximum aperture that we're gonna be looking at. So this is the opening that all the light gets to come in through the lands. So how big of aperture do you have on your lens? And this is the maximum aperture and they come in. A variety of different numbers will go down 1.4, some will go beyond it, and 5.6 is the maximum aperture on one of these giant super telephoto lenses. And this is gonna be listed right on the front of the lands. And it's listed in kind of an unusual fashion. That kind of confuses some people, and it's a one colon 1.4, and I know that I've heard some people they didn't know what they were talking about. This i...

s Yeah, I have a 1.1 point four lens. I know you don't you have a one colon 1.4 lens, and what that means is that it's a fraction, and this is how you write fractions when you don't have to lines and you have a typewriter and you just have one line of information. This is how you write a fraction, and what it means is the focal length of the lens over 1.4. Now the focal length of this lens is 50 millimeters, and so it's a math problem. 50 millimeters, divided by 1.4 gives us millimeters and 35 millimeters is the opening of the lands, and so you can I know this sounds like a lot of fun. You get to go home and run on and divide all your lenses by this, and you will see what the opening is of any of the lenses that you have. That's the maximum open E. So a 50 millimeter lands has a maximum opening of 35 millimeters Now with cannon, they also have a millimeter 1.8 lens that has a 28 millimeter opening, and they also have a 50 millimeter. 1.2 lads. It has a 42 millimeters. Now, I will let it be up to you to guess which one costs more money. All right, but yes, Bigger lenses air. Gonna You're going to spend more on it, but it allows you to shoot under lower light levels. Now, if you want to run this math with other lenses, the 24 14 only needs a 17 millimeter opening because it's a very short focal length lens at 24. Ah, to 8 is gonna be a really big leads. And it needs a really big opening, even though it's only 2.8. So you can run this math to figure out how big of opening does it need toe let in that amount of life? And so the maximum aperture is the lenses maximum opening, and it's gonna vary from lens to lens. And there are lenses that we consider fast and lenses that we consider slow. Ah, lens. That is one point fours. Considered a fast lens, it's considered fast for a couple of reasons. It it acquires light very quickly, so it can very quickly acquire the light that you need, which ends up being fast shutter speeds. And so we use fast for a couple of different reasons. And then there are slower lenses, which typically have maybe, ah, larger zoom ranger there longer telephoto, and it's more difficult to get all that light it in there. Photographers love fast lenses because they give us options at shooting under very low light conditions. We'll talk more about that. So the maximum aperture on zoom lenses, the most common lens and photography these days is the 18 to 55 to 5.6 lands, and so this is what is known as a variable maximum aperture. The maximum opening will adjust as you zoom lens from 18 to 55. Same thing on a 300. It adjust is you zoom the lens back and forth. There is in a fixed maximum aperture, for instance, a 24 to 1 20 EPH 4 24 35 51 20 F force the maximum aperture In all those cases, these are more convenient to use in my mind because if you set your camera manually and you decide. I want this shutter speed this aperture this I s O and I'm gonna shoot a photograph. Well, no, I would like to adjust the zoom lens a little bit. You don't need to make any further adjustments on your camera. If you do that with the variable maximum aperture, you may need to make an adjustment, depending on where you have set your aperture on it. And so these are more money. They're more expensive to make, but they do tend to be a little bit more preferred by people who do a lot of manual exposure. There's a lot of record holders and top of the top of the field as far as the fastest lenses in any particular category. And so there's a lot of 1.4 lenses that are the fastest of any particular Focal Inc at around 50 51.2, eyes going to be a very fast lands. The 1.2 is a very fast portrait lands, and you saw earlier I did some examples with the equivalent 56 1.2 for crop frame and a 42.51 point two. They all have the same fast aperture. But you do get a different depth of field because you have a different size sensor recording those images. And so when you get up to the tele photos, sometimes F 2.8 is as fast lens as they make. And when you get all the way up to 800 the fastest Lenz they make is a 5.6. And there are a number of ways of going even beyond it, like a makes a 0.95 And why do they make it is a 0.95 and they just don't make it a one or just rounded up toe. One bragging rights under one point. Oh, but then there are some other after market manufacturers that could make some really fast things. And there are some people who kind of like who fast lens. That's kind of cool. I got to do more of this more, more, more, and then they start going to all sorts of extremes, and what you'll find is in the optical industry. Beyond photography, there's X rays and medical and other things that they have designed lenses for that or even faster than 0.85 It's just that they're not very good optically it, developing what we would call normal photographs. They can create images, and so there's some weird aftermarket things out there. But for the most part, 1.4 is gonna be a pretty fast lands for most people in most situations with zoom lenses, they're more complicated to make, so they tend to be slower in their aperture. And so a 2.8 lens is kind of the gold standard for most zoom lenses. If you have a zoom lens with a 2.8 aperture, that's a lot of light for a zoom lens. And so 24 to 70 72 to hundreds, these air mainstays of professional photographers there are some longer telephoto lenses that'll go up to F four. Sigma is a manufacturer that has really come on strong and made some unusual products. Yes, they do have a 200 to 500 to eight. It should probably come supplied with its own car so heavy they do have very interesting the introduced recently a few zoom lenses. The 24 to 35 F two is designed for full frame lenses, and it's one of the Onley. Maybe the Onley zoom lands faster than 2.8 for full frame cameras, but for the crop frame, they do have some 1.8 zoom lenses. And if you run the equivalent aperture math, these this 50 to 100 is the equivalent in angle of view and in depth of field to a 72 202.8 lens. And so, if you like that shallow depth of field, you will get that same effect with a 50 to 100 with the added benefit of being able to shoot at 1.8 for really low light situations. So there are some interesting options out there now. The faster these lenses are, the bigger and heavier they tend to be. Now you might be wondering if you're new to photography. You sound pretty passionate about these really fast lenses. You know? Why do you hold these in such esteem? There's a lot of benefits toe having a faster lens. They just give you more options for solving problems. You can shoot under lower light levels. You can shoot with faster shutter speeds and so it opens up new possibilities. The brighter viewfinder is for those of you with SL ours because when you look through a lens on an SLR Nikon or Canon Pentax, you're seeing your lands at maximum aperture, and the bigger that opening is, the brighter and easier it is for you to see your subject in there. In many cases, that's gonna mean that you're gonna be able to focus faster cause there's more light committed for your camera to focus. And so I know that using a 2.8 lens or faster when you're shooting sports is there is a big advantage. The lens of the cameras just seem to do better with 2.8 lens is than they do with four or 56 lenses because there's more light coming in. So more like coming in. It's a good thing, but it's expensive, and it could be heavy. So it's a compromise. Like everything else in photography,

Class Materials

Bonus Materials with Purchase

Photo Vision
Course Outline