 A camera is essentially just a box. It looks kind of like this. And on the front end of the box, there is a hole. You might recognize it more having a piece of glass in it, but in essence, it is just a hole. And now you can imagine on this camera that it would go back like this. Maybe it would be different shape, but we're just going to make it into a very simple box, and we're going to view it just from the side. Now, light enters this box through that hole, and in modern cameras, it is always with some sort of piece of glass, and we'll talk about lenses a little bit later. But that light is focused through that hole in the wall. Inside, there's no other holes anywhere else in the camera, just in the front. And that light is focused through that hole, and then cast onto the back wall of the camera. Basically, if you remember the history lesson, it's just like a camera obscura. It's the very same principle. So we're going to step back a step here. We're going to delete a few pieces of our camera. And we're going to add in something that was very important in the development of the camera, and that is the lens. So here's our body. They made the hole a little bit bigger so that they could mount a lens on it. And we're going to make our lens green. And we'll make our lens sort of like this, right here. And we'll put it in kind of a long lens, like this. All right, so here's our lens. And we're going to say it kind of comes in here a little bit, right there. All right, now inside of that lens, so I just made the outside bit of the lens, inside of the lens, is some glass. So there's usually lots of pieces of glass. So we'll say here's one piece of the glass, and maybe there's another right here, and maybe there's some space. Have a piece of glass right here. Maybe there's another piece right here, and right here. And at the very end, there's another piece of glass right here. Now what happens is the same way that light came in before, light is cast over onto the lens. It travels through, and it comes out the other side, and lands on the back of the camera. And just like before, red comes in, bounces around in here, takes a little trip, and is then in the end, cast in this direction, like that. So you get an idea of how all of that works. I'm going to go back a few steps here, and delete that. So you've got your light coming in. I'm going to reintroduce our light streaks here, because I think they're kind of cool. And this is basically the same principle. This is still a camera obscura, because we don't have any film yet. It's a camera without film, which is a camera obscura. And you could, in theory, if you were small enough, you could jump inside the camera, and you could draw what you were seeing on the back wall of the camera. Now at some point, like you might have seen in the history course, or in the history lesson, some people figured out that there were light sensitive chemicals. And so at some point, someone came up with the idea of making film. So film was produced, and we're going to make our film brown, and it was put in the back of the room, or in the back of the box, in the back of the camera. So here's our film. And this is basically, early on it would have been glass, or some piece of metal, covered and coated in some sort of light sensitive, silver nitrate of some kind. And eventually it became a piece of plastic, or something along those lines, and then it would be covered in the silver nitrate in a dried form. Early on these actually were glistening wet. They would stick them in, take the photograph while the plate was still wet, and then they'd take it out and go develop it. So this is a sort of a situation where you now need to find a way to keep the film from being exposed while the camera is exposed to light. Because right now, if we were just to have your film sitting in there, it would always be exposed to light. So you need to make a shutter. Early shutters were actually often inside of the lens. And there was just a little door that you would pop open. The light would come in, and it would hit the film, and expose it. And then you would pop it back down, and the light would stop, and that was your shutter. But as film got faster, the shutter needed to become more quick. And there are still cameras that use a lens shutter type. But in general, most shutters on most cameras are going to make the shutter on this camera red. Are right in front of the film. So the film is sort of in a case of some kind. Something like that. And then in the front, there's basically a big door. And sometimes it's a series of tiny little doors that all open at the same time, something like this. And they're all kind of connected. And so when the picture is being taken, all of these, sort of like the blinds in a window or something, they all pop forward or pop down, however the shutter works. And they slide. They slide down, and then they pop back up into place. So it's almost like those kind of blinds that you have on your windows that you can open and close by twisting the handle. It's sort of a similar situation, but at the same time as they're sort of changing their horizontal tilt, they're also sliding up and down. And that basically creates a very small moment where light is then cast on the film. So your film is protected from being exposed, and then it's exposed to the light, and then it's close to again. So this represents then the basics of photography. This is really, these are the most essential elements to a camera. There's also the problem that you can't necessarily control the amount of light coming in with this lens. You just have a set amount of light that you always have to work with. That brought about the idea of the aperture. The aperture is kind of a little bit more of a confusing concept, and we'll talk about it more in another lesson. But basically what aperture is, is it's kind of like shutters for your lens. And often that piece of machinery is either here in the lens, so right where my arrow is, or kind of more forward. And we'll make ours up here because we just have space for it. I didn't leave space back here. From the side, it would look something like this. From the side, it would look like a little hole. And basically, this is a piece that you would twist like sort of a wheel that's on the outside of your lens. And it will close and open this window. So from the front, if you were to look at the front of this piece right here, you have your lens. And then you have what are called blades. And they're all sort of going like this. And there's a little hole in the middle. And as you turn this right here, this sort of grip, as you turn it, this hole gets bigger and smaller. So you can control the amount of light that's coming in. It's sort of like opening and closing the shades on a window. And this has the effect of allowing more or less light in, which has lots of purposes and lots of uses. And we'll explain those later on when we start talking about aperture more in depth. But just so you know, that is how aperture works. So I'm going to delete our little diagram here. So we've got aperture. Now comes the problem of the viewfinder. Now we're not exactly sure how we're going to see all of this. Now we're going to make this camera into what's called an SLR. Now there's lots of different types of viewfinders. One, the early viewfinder was just basically two squares. You'd just make two little squares on the top of the camera. And then with your eye, you would make these little boxes so that when you looked through it over top of the camera, you would see about what your lens would see. But this is a pretty primitive way of doing it. My first ever camera had one of these. And it was just a little $2 camera that my mom bought me for my birthday when I was really small. And it does work. It works really well. But it's not the most advanced way to see it. So eventually, over time, there have been lots of different ways of creating a viewfinder. This is something a little bit like what you would call a rangefinder, something along those lines. But what would eventually come to be the standard in photography, or what is considered the best solution to this problem right now, or one of the best solutions to this, is what's called the single-lens reflex. So we're going to add now a mirror to the whole situation. So we'll take a mirror. And so the light would normally be coming in and hitting this and just not going anywhere. But what scientists and camera makers decided to do was try putting a mirror right here. They've put in a mirror. And this reflects the light up. So your light comes in right here, hits the mirror, and goes boing right up to the top of the camera. So up here, they made it very complex. We're going to add some more hardware to our camera here. Made a very complex little set of mirrors and prisms. So the light goes up, and it lands inside of a big prism that is sitting up in the top of the camera. And I'm not exactly sure how the light bounces around. There are some good diagrams of it online. But you take your eye. Here we've got our eye again. And it's looking into this. There's a hole right here. And it's a little window that looks right in to this. And basically, the light is going boing, hitting the mirror, going up, up into here, bouncing around a little bit. Now this is not accurate, obviously. I didn't do a very good job on this. And then it's coming back out right here. So the light, you're seeing it go all the way up. Ding, go this way, go that way. There must be something like that in there somewhere. And the light comes back. And you can see exactly what this lens is seeing, what you're seeing through this lens. Now when you want to take the picture, you push the button, and this piece of mirror, well, I made it a little too big so it wouldn't look like it would work. But this mirror would flop up to an up position. So the mirror, when you're taking a picture, is right here. So there's a spring on it that has a hinge. And it just goes, ding, pops up. And you can imagine it not being here anymore. And then that light passes through that there. And then the shutter opens while this is happening. So you're pushing the button has done two things. It's open the shutter. And it's popped the mirror up. And then the light travels in through the lens to hits the film, exposes it. And then when the camera says that the exposure is correct, then everything closes back down. So the mirror drops back down, the shutter closes, and the film is exposed. The only thing that they've really done in recent times that changes any of this is that they've taken this piece of film, and they've developed digital sensors that can basically do the same thing. And actually now we're learning do a lot more even. And they've replaced that. So we've got a digital sensor. And they've added some sort of memory space. So we'll just imagine that this is like a little card down here. This is what you save your files on. So the light comes in, hits the digital sensor. And the digital sensor is just like a little series of electrical nodes that sense the light. And then they pop out bunches of ones and zeros. And they go through, put a little computer in here. So there's a little computer here, right there. And the information goes into the computer. Computer processes it, saves it as a file, and drops it into your card. And your picture is now here on your card. And then you take that out, put it in your computer, and use it. But sometimes you won't maybe have a mirror here. There's lots of different ways of doing this little part here. But this is basically how it works. They've added also, in recent years, screens. So on the back you've got, even with the early digital cameras, you have a screen, just a TV version of this. There might be some sort of, either the shutter is a different kind of shutter. And the sensor is always exposed to the light. And so you're seeing directly what the sensors use. Or they have some sort of system that does the same purpose of taking this light that you're seeing. And instead of displaying it up top, they just display it on a screen. So that was our lesson for today. 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