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  • DAN: All right.

  • Everybody, welcome back to another week of exploring digital media.

  • This is our second lecture here in the cinema.

  • And this week we're going to be talking about framing composition and lens

  • basics.

  • And we'll actually tackle this in the reverse order today.

  • We're going to start with lenses.

  • So let's dive right in.

  • We have two typical types of lenses.

  • We have prime lenses and zoom lenses.

  • And who wants to give me a quick definition?

  • What's the difference?

  • Yeah.

  • AUDIENCE: A prime lens is a fixed focal length,

  • and a zoom will have a range from 70 to 200 [INAUDIBLE]..

  • DAN: OK.

  • Yeah.

  • So we have a fixed focal length on one, which means you can't zoom.

  • Right?

  • And a zoom lens or a variable focal length lens can zoom.

  • Which means you can literally crank a ring on the lens

  • and the image other enlarges or gets farther away.

  • Right?

  • All right.

  • Great.

  • Prime lenses.

  • Construction is pretty simple.

  • Inside we have a couple of lens element groups

  • that when you turn the focus ring, some of them move,

  • bring your image into focus or out of focus.

  • And a zoom lens is a bit more complicated.

  • As we look at this cross section here you've

  • got a couple different lens groupings that

  • move to either zoom your image in or zoom it out.

  • And also change your focus.

  • But I mean, look how complicated this thing is.

  • Look how many lenses we have and how many moving parts there are.

  • It's pretty crazy when you actually look at it.

  • But why might we choose one or the other?

  • Let's talk about some pros and cons.

  • When would you want to have a simple prime lens or a zoom lens?

  • Who's got some use cases for me?

  • And zoom, feel free to-- if you're in the distant audience feel

  • free to chime in as well.

  • Yeah.

  • AUDIENCE: I guess you would use a zoom lens

  • if you want to be able to respond to the [INAUDIBLE]..

  • DAN: OK.

  • So when you want to respond quickly.

  • OK so maybe you don't know what's going to happen.

  • You're covering an event or and you need the versatility.

  • Yeah.

  • That makes sense.

  • How about an argument for a prime lens?

  • Yeah.

  • AUDIENCE: When you want to isolate your subjects with a shallow depth of field.

  • DAN: Oh.

  • A shallow depth of field.

  • OK.

  • But can you not have a shallow depth of field on a zoom lens?

  • AUDIENCE: You can if you zoom all the way up to 200.

  • DAN: OK.

  • AUDIENCE: [INAUDIBLE] aperture.

  • DAN: So maybe there are some tricks to getting a shallow depth of field

  • with the zoom lens.

  • But maybe it's easier on the prime lens?

  • Is that always the case?

  • AUDIENCE: No.

  • But [INAUDIBLE].

  • DAN: Not necessarily.

  • So there's something in a zoom lens' construction

  • that might make it easier to have a shallow depth of field.

  • And we're going to talk more about what that means

  • a little bit next week when we talk about exposure.

  • Anybody have anything else?

  • How about our zoom audience?

  • Somebody give me a benefit of a prime lens over a zoom lens.

  • Just open your mic up and start talking.

  • Yeah.

  • AUDIENCE: Say it again, Alex.

  • DAN: Go ahead.

  • AUDIENCE: I think maybe prime lenses let in more light basically.

  • DAN: Let in more light.

  • So prime lenses tend to be faster.

  • Right?

  • They actually let more light down the barrel of the lens,

  • which means you get better low-light performance.

  • All right.

  • Great.

  • AUDIENCE: Prime lenses are lighter.

  • DAN: Prime lenses are lighter.

  • All right.

  • So the physicality of the lens is much smaller.

  • Easier to move around.

  • If you're going to carry a camera with you maybe

  • you're taking a prime lens with you.

  • Exactly.

  • Right?

  • So They're also-- they tend to be cheaper

  • because the construction is simpler.

  • We said faster.

  • I like to put forced creativity here because with the zoom lens

  • people stand in one place and will just zoom in or out to get

  • the shot that they want.

  • But it really forces you to get creative.

  • You have to actually get closer to your subject or farther away.

  • So I think that it's a really handy way as a starting photographer

  • to challenge yourself to build a more complicated frame.

  • They're lighter.

  • There's less to break.

  • So if you have to replace it, it's cheaper.

  • And zoom lenses tend to be more expensive.

  • They're slower as far as how much light comes down the barrel of the lens.

  • But you do get that versatility.

  • Right?

  • If you're going to cover an event it's much easier to have a zoom lens

  • so that you can snap in or snap out, depending

  • on what's happening with the action.

  • Or even if you don't want to carry a bunch of lenses with you.

  • Let's say you're going out to shoot in nature

  • and you just don't want to carry three lenses with you so

  • that you have the options.

  • A zoom lens will give all those to you.

  • All right.

  • So there are three categories that we define lenses in.

  • Either a wide-angle lens.

  • a normal lens, or a telephoto lens.

  • Are the three typical ways that we define these.

  • The three categories of lenses.

  • And so let's first just think about what we see with our human eye.

  • OK?

  • So we have a peripheral vision of about 180 degrees which is pretty wide.

  • But we can't focus on everything in our peripheral vision at once.

  • The area that we actually can kind of focus on is called your foveal vision

  • and it's about 40 degrees wide.

  • Which is pretty narrow when you think about it.

  • So a camera lens all have different fields of view.

  • And they're typically marked with this marking over here

  • that is something in millimeters.

  • So the lens on screen here is a 50-millimeter lens

  • and it has a field of view of 46 degrees.

  • And I have a little asterisk down here that's

  • on a full-frame 35-millimeter sensor.

  • And we'll get to what that means in a second.

  • And we measure this diagonally on the image.

  • So diagonally across an image.

  • And I do sneak pictures of my kids into my slides.

  • From corner to corner we have a 46 degree of view.

  • And that's just kind of interesting.

  • It's not the reason that a normal lens is called--

  • or a 50-millimeter lens is a normal lens on a full-frame sensor.

  • But it's just interesting that the degree of view that you see--

  • that you can pay attention to in any detail

  • is similar to what a normal lens is.

  • But really a normal lens defines the spatial relationships between objects,

  • whether things are distorted and pushed farther away--

  • or compressed in on top of each other.

  • A normal lens has the same properties of what your human eye sees.

  • So again, a normal lens on a full-frame sensor

  • is about 50-millimeter will just give you

  • a typical spatial relationship between objects that you see down your lens.

  • All right.

  • So a telephoto lens is anything that's zoomed in.

  • And I have pictured here prime lenses but certainly,

  • zoom lenses or telephoto as well.

  • This is an 85-millimeter lens, which has a field of view on a full-frame camera

  • of about 28 degrees.

  • So we're really narrowing down our field of view at this point.

  • Whereas the wide-angle lens is the opposite.

  • Right?

  • So a 35-millimeter will give us about 63 degrees for the field of view.

  • So which you might choose depends on what story you're going to go tell.

  • How much of an area do you need to see?

  • We've talked about what categories we have lenses in.

  • Let's now play a game where we can actually look at images

  • and describe what qualities we see in these.

  • So we'll play a little game called wide, normal, or telephoto.

  • All right.

  • And how we play this is, I'm going to put up an image.

  • And you're going to tell me, what do you think?

  • Are we looking at a wide-angle, a normal, or a telephoto?

  • So someone in the audience here.

  • Yes.

  • AUDIENCE: Wide.

  • DAN: This is a wide-angle lens.

  • Why do you say that?

  • AUDIENCE: Because of the distortion with the ducks

  • are closer to the front element of the lens.

  • And you can see a lot of the background as well.

  • DAN: OK.

  • So I'm hearing that we have a lot of distortion in the lens.

  • Right?

  • So what is it that is distorted in this image?

  • AUDIENCE: The beak and the duck's head because that's not how the ducks look.

  • DAN: OK.

  • So this isn't quite how a duck looks.

  • Right?

  • This is kind of a wild looking image.

  • Right?

  • And it's the distance in this image that's spread out.

  • Right?

  • Like we're elongating the ducks nose because we're so close to it.

  • Right?

  • And the distance behind it is really--

  • things spread out and get really far away.

  • Even though these ducks aren't that big.

  • Right?

  • The trees presumably aren't as far away as they might seem in this image.

  • Right?

  • AUDIENCE: Right.

  • DAN: Very good.

  • And so this it's actually a very wide-angle lens.

  • The 35-millimeter equivalent is 7.2 millimeters.

  • So that's a very wide-angle lens.

  • How about this one?

  • Oh, crap.

  • I left it up there.

  • Spoiler.

  • Why [? done with a ?] telephoto?

  • I'll just stand over here.

  • Somebody else.

  • Ian, what do you think?

  • AUDIENCE: I don't know.

  • If you look at the width of the road and how it gets smaller

  • and the background-- the difference between proximity and sort

  • of the expansiveness of the space.

  • I'd say it's probably a little bit wider.

  • Maybe would be my guess.

  • DAN: So you are correct.

  • This is another very wide-angle lens.

  • The equivalent is 11.9 millimeters.

  • Another road.

  • So similar to what we just looked at.

  • Does this one feel different than the wide-angle lens we just saw?

  • Anyone,

  • AUDIENCE: Yes.

  • DAN: Right.

  • Yes, Dan.

  • It does.

  • It looks quite a bit different.

  • Right?

  • So instead of the road being wide up front as Ian said,

  • and narrowing off very quickly, it's almost the same shape all the way down.

  • And what is further away in the image feels much closer.

  • Right?

  • So we're probably looking at a--

  • AUDIENCE: [INAUDIBLE].

  • DAN: --or even a telephoto lens in this case.

  • I jumped right over normal lens and went right to telephoto.

  • So this image has a 135-millimeter lens on it.

  • This image does.

  • So this is actually a telephoto lens.

  • And things-- we're looking at a compression of space.

  • Whereas the wide-angle lens distorted and exaggerated distance.

  • A telephoto lens does the opposite.

  • It compresses space.

  • How about this one?