Choosing the Right Camera Lens


Choosing the Right Camera Lens


Lesson Info

Equivalent Aperture

This is something that I did not learn about in college, because when I was in college, we shot with 35 millimeter cameras, and we shot with four by film cameras, and they were completely different, and we never talked about equivalent aperture. But now that we have cameras with different-sized sensors and a variety of different lenses, we want to talk a little bit about the aperture equivalents, because in the previous section, we were talking about the focal length equivalent. So let's take a couple of lenses. We've got a full frame camera on the left that is shooting with a 50 millimeter lens. Over on the right-hand side, we're shooting with a 35 millimeter lens, to get the same 40 degree angle of view. So, is the photos that you take with these two cameras exactly the same? Well, the angle of view is the same, and let's take a look at what lenses, say if we were using the 50 millimeter 1.4 and the 35 1.4, well then we would be letting in the same amount of light. But they're differ...

ent lenses, and so things are gonna look a little bit different. And where things are different is in how shallow the depth of field is. The 50 millimeter lens is gonna render a shallower depth of field than a 35 1.4, even though it sees the same angle of view. Angle of view and depth of field are different subjects. And so, if we stop the 50 millimeter lens down to f/2, then they start to look very, very similar. Now this is a subtle difference to people who are kinda just getting into photography, but as you get more and more into photography, you're gonna notice a particular look from a particular lens. Let's try this with a 300 millimeter lens on a full frame camera and a 200 millimeter lens on a crop frame camera. These are gonna be shot at f/5.6, so they're gonna have the same amount of light coming in, but we have a different-sized sensor. And the lenses are gonna render differently. If you look at that tree in the background, you'll notice, with the full frame camera, you are getting a shallower depth of field lens. If we stop it down to f/8, it's a little bit closer to the 200 at f/8. And so as we stop these lenses down, the full frame is always going to give you a shallower depth of field. Now, some people will immediately assume that a shallower depth of field is better. Well, not necessarily, sometimes it is, sometimes it's not. And so it depends on what you're going to shoot. And so, there's a lot of forums and places where you can talk about photography these days, and one of the most common arguments is about equivalence from one size sensor and lens to a different size sensor and lens. And so if you have a full frame camera with a 50 millimeter 1.4, it sees the exact same angle of view, roughly, as a 35 1.4 on a crop frame camera. They let in the same amount of light, and you're gonna set the same shutter speed to get the same exposure. What's different is the depth of field that you get, because a 50 millimeter lens will have shallower depth of field than a 35, the depth of field will be different. And so the same aperture gives you the same low light ability, the same focal lengths give you the same depth of field. In these examples, we have different focal lengths that are gonna give you a different depth of field. And so when people are saying, I have a lens on my crop frame camera, and it's the equivalent to something like, something else, somebody's likely to get mad and say, it's not the same! Well you can say, it gives me the same angle of view, and it gives me the same aperture opening, but a different depth of field. And so there's three characteristics, there's the angle of view, there's the aperture, and the resulting depth of field. And when we talk about equivalence with crop frame cameras, you can get two of them the same, but that third one is a little bit difficult to get to. You have to get a different aperture to get the same depth of field. So it's a little complicated but you'll learn it as you practice it and continue shooting.

Class Description

Once you’ve chosen the camera of your dreams, how do you know which lens will maximize your camera’s capabilities? Join camera expert John Greengo as he explains what the best lenses are to add to your camera bag. He’ll explain:

  • Which lens is best for specific areas of photography
  • The technology behind lenses
  • How to use specialty lenses including macro and fisheye
  • Tips on operating and maintaining your lenses

John will also talk about lens accessories including hoods, mounts, filters, and teleconverters. By the end of this class, you’ll understand exactly what lens you’ll need to take your best photos!