TechStuff Classic: Slow Motion Film and High Speed Photography

doing this a long time. So this episode is where Chris Pallette and I take a close look at the technologies behind slow motion film and high speed photography, which are closely related. What is necessary to make those works, specifically in the world of film, more so in film than in video. So I hope you enjoyed this classic episode. Today we wanted to talk about high speed photography and

slow motion. Both of these have to do with changing film speeds and shutter speeds and all this kind of stuff. To really talk about how this stuff works, we have to go a little bit more basic. We have to actually talk about the principles behind photography and how a

camera works. And before we really get into this, How Stuff Works has dozens of great articles about photography, including articles about how high speed photography works and how burst photography works, both of those written by John Fuller, but we also have how cameras work, how photographic film works. So if you want to learn more than what you know,

we're gonna kind of cover the basics. But if you really want to know the true science and chemistry and physics behind how cameras work, I highly recommend you check out those articles because they will answer a lot more questions. We're gonna try and kind of cover the basics here. So so let's, uh, let's talk about what a camera does. It's seems kind of silly to say because we're most of us are really familiar with cameras. And by the way, I should point out also that we're really focusing on

film film. See what you did there, It was completely not on purpose. Um, we're talking about film cameras mainly in this podcast as opposed to digital. The two different methods. You know, you get the you get a result that's similar using these two methods. You know, you get an image of a moment in time in both ways, but the actual mechanics behind film versus digital are very different.

So we're specifically looking at it's going to say focus again, looking at film cameras because well, to to try and cover both would require like a podcast that's twice as long as what we normally do, and we only do that for Google Plus. Well, UH cameras in general though, um, and speaking of both film and digital, you're you're you're using a series of devices to capture that image. There. On both film and digital you of course you've got a lens um and there is uh, the principle behind

it is to capture the image. On film, you're using a a piece of essentially plastic celluloid to that's treated with chemicals that captures that image. And and a digital camera use an image sensor. UM. But you know, and and there are some similarities. Of course, it has to do with how fast the camera is firing um and how much light you're letting in through the lens um, and after that they do differ considerably so with a with a film camera, you know, Chris was just talking

about it a second ago. But what you know, the main the medium upon which you are capturing these images is film, and film is really just a strip of plastic that's been treated with uh, with chemicals that are photoreactive. Yes, that means that the chemical coals will undergo some sort of change when exposed to light, so they turned into monsters. If you've listened to our Solar if you listen to our Solar Panel episode, you know that we have discovered

materials that react when light hits it. The photons from the light transfer energy to whatever that medium is and you get a reaction. In this case, the photons are able to change the chemical properties of the stuff that's on this film. And I really get into that would be diving deep into science. We do have, like I said, the article on how photo, how film photographic film works,

and that explains it. But um to be honest, if I were to try and go into it right now, I'm sure I would mess it up because you know, my my chemistry is only goes so far. My chemistry food is weak chemistry. But at any rate, what this this stuff is designed so that when light hits it, it has a chemical change. Then when you treat it with other chemicals, that's what allows you to create a negative image of whatever it was you were whatever light

hit it. So this is why when you have film, people say, you know, make sure you don't expose it to light before before or after you take a photo, because if you do, it's going to ruin the image, right, because um, the film is going to record the light from the that that is coming to it through the lens. So of course, when you put the canister a film inside your camera and load your camera, you close the

door which blocks off any light. Um. And then of course you have to advance the film after you've taken a photo. If you if you've ever exposed film more than once, double exposure, you get a really bizarre effect. Yeah. Yeah, and it can be very very cool if that's what you're going for. It can also be really frustrating if you were trying to capture one thing in particular and

forgot to advance the film, right. And and we've even seen that double exposures go into uh the realm of people thinking that something supernatural is going on, because you do get kind of a ghostly image if you double

exposed film. Yeah. So there have been times where people have had just a double exposure, that's all it is, but because they didn't realize it was a double exposure, they say, wow, I took this photo of my buddy Bob, and there's this ghostly face that's appearing over his left shoulder. That's so creepy and not forgetting that. Oh, before I took the photo of Bob, I took a photo of Liz. It's just that Bob's photo was exposed over Liz's photo

and now Liz looks like she's a ghost. Actually, I thought it was because Bob worked at that leaky nuclear plants. Because we took all those photos over that Indian burial ground. That was the mistake we made. Anyway, um uh. The the the idea here is that the camera gives you a very controlled way to expose that film to light. And the way this works is at first you've got the lens and the lens is purpose is to direct light to the film, So the lens is allowing light

to pass through. When light passes through a lens, that actually the speed of the light changes. You know, speed of light is a constant, but it's a constant that's based upon whatever the medium it is that is traveling through. For example, air, Yeah, air, it's going to travel through it. Light travels through air much more quickly than it will a lens. And the curvature of the lens, the thickness of the lens. That's all going to make the light

travel at slightly different speeds. The point being that you focus all that this light onto a point so that it exposes just the right spot on the film. Now, behind that, you've also got a device called the aperture. Now the aperture is essentially a hole. It's a it's a it's a disk that can expand or contract and allow more or less light to pass through the from the lens to the film. So it's it's a barrier

between the lens and the film. And you adjust this in order to uh to really kind of tweak your photo settings, like with a with a manual camera manual single lens reflex camera or SLR manual SLR UH by the way, in case you're curious, for those of you who are only familiar with digital cameras, a manual single

lens reflex camera is not electric at all. It's it uses chemicals and it uses mechanical little gears and things, but there's there are no electric components necessarily in a true manual single lens reflex or at least you don't have to have any electronica. I think that's so. In other words, It's kind of interesting because we we take

it for granted now with digital cameras. Right, digital cameras, you have lots of electronic components, but with a a an old manual single lens reflex, you're just you, You're just turning little dials, which is advanced the film. You might have turn a little crank to rewind film, but there's nothing necessarily electronic in it. Um of course, there are hybrids that as well, but anyway, this the aperture helps you determine how much light can enter through the lens.

And then you have something else called the shutter, and the shutter determines how long the film is exposed to that light. So if you were to take a photograph with a shutter speed that is a you know, it allows the shutter to be open longer, then your photo is going to be a little more blurry, unless the

subject of your photo is incredibly still. So if the camera is still, and the subject is still, and you've got a decent amount of lighting, and the shutter is open longer, theoretically, as long as as long as the light's not too great, you will actually get a very clear image because it's it's really upturing that uh, that moment um. Now, if something is moving, then you're gonna

get a blur. So if you've ever looked at some nighttime photography, especially for like city scapes where you can see where traffic is moving through and it's like beautiful red streaks on one side of the road and white streaks on thegether that you know, that's obviously the traffic where cars are coming and going. That's usually using a camera with a shutter speed where the shutters remaining open longer.

Sometimes it can be as long as you know, minutes or or more, and that creates that streaking effect because all that light is hitting the camera over an extended time. So instead of seeing individual cars, you're seeing these streaks. Yeah, this this has basically it's a combination of things. It's a combination of the aperture setting that you're using to expose the film, uh, the shutter speed, and there are cameras that you can manually hold the shutter open uh

as long as you want to. It's often better and and creating the photos like Jonathan was just talking about, where you leave it open for minutes, to have your camera on a tripod and use a cable release, you know, just so that you don't nudge the camera because otherwise you're going to uh jar the picture and distort things. So yeah, it also has to do with the speed of the film. And uh it's funny because that's sort of a misnomer and you know, there aren't little canisters

of film moving faster than others. It has to do with the chemical properties actually the um and again we're not going to get into the chemistry behind it so much. Um, but uh, you know, depending on the speed of the film, you would be able to capture uh photos in darker environments or lighter environments. Um. Also, the speed of the film has is depending on on the type of photography

you're doing. If you're trying capture high or fast motion photography, you're gonna want something that you can expose um to light more frequently, like a higher speed film. Yeah. Um, you know, you want something that's going to to just from a very brief exposure be able to capture an image. And and by exposure, we're talking about exposing to light. You know, just keep that in mind that that exposure has everything to do with the amount of light and

the duration of light that hits that film. So a high speed film can capture an image with light hitting it for a shorter time frame. And we're talking fractions of a second here. You know, when we talk about

a short time frame, we're talking really short. We're not talking like, oh, well, you know a woman thousand two a dozen Now, you would be able to take hundreds of photos in the amount of time it took me to say that, depending on the speed of the film and the shutter speed and all of this kind of stuff. Chris and I will have a lot more to say about slow motion film and high speed photography in just a moment, but first let's take a quick break to

thank our sponsor. So high speed photography kind of leads us into this. High speed photography is all about trying to capture, uh an image of something that's moving at an incredible speed, something that that is moving so fast that to the naked eye it may be either a blur or perhaps even you know, practically invisible because it's going so quickly. But you want to be able to capture that moment in time so that you can see

a very distinct image. Well, this is a challenge. You have to figure out how are you going to do that? And there a couple of different ways. Perhaps I hesitate to say the easiest way, but perhaps the simplest way is to set up your camera in a perfectly dark room and you just leave the shutter open. Because remember, even though the shutters open that film, if there's no light, the film is not being exposed. So you've got this

film that's just sitting there, nothing's happening to it. It's not reacting chemically at all because there's no light coming into the camera. You set up whatever the thing is you want to take a photo of, and then you have it timed out so that the instant that thing happens, there is a flash of light right that is up and down in a fraction of a second, and just that fraction of a second is going to be long enough for the light to go through the camera and

uh and to expose the film. Then you could advance the frame and do it again. Now, this is a very slow, painstaking process, and it requires an incredible amount of timing. And there are a lot of different ways of setting up a shot so that the the the light will trigger at the right moment. Some of them are acoustically triggered so that there's a noise, and that noise causes the light to flash, which automatically exposes the

film in the camera. You don't have to do anything to the camera at that point, right, you're not pushing a button because the camera shutter is already open. It's only after the light is flash that you have to advance the film so that you can take another photo. Otherwise you're going to have a double exposure, high speed double exposure on this this film, which I think would look really weird. Um. So that's one way you can

do it. But of course, if you want to take a high speed photo of something in nature, for example, the the an example that a lot of people use as a hummingbird, because a hummingbird can be its wings so quickly that with most cameras, if you took a picture of a hummingbird with a standard camera, it's gonna look like a bird with two blurs next to it, right,

you won't be able to see the wings. Um. But if you use a high speed camera where it's able to move the shutter at a really fast rate, and you have a pretty well lit environment, then you might be able to capture an image of a hummingbird where you've got its wings perhaps in the upper down position, and you can get a really clear look at that bird.

But it does require that you have a camera that can move that shutter speed at a really really fast rate, and that you have a high speed film that's capable of taking light for a incredibly brief exposure time and convert that into an image. Yeah. You know, UM, if you're a tech stuff listener normally, UM that we like to get into the history of things, and I wouldn't necessarily have thought of high speed photography is I would have thought it was a more modern, um, something that

was more modern phenomenon. But really the history of high speed photography goes back just about as long as the history of photography itself. UM. The first example that I I read about, um uh from a a uh an article by Lincoln l Endelman, which was William Henry Fox Talbot's uh AH trial, where he basically exposed a piece of the London Times newspaper that was on a wheel that he attached it to, and he was using a wet plate camera, which is basically a piece of glass

that's treated with chemicals rather than a film camera. Interesting. I had never heard of that before. There was eight one. I've heard of the camera obscura, which, by the way, you can actually build one of those yourself if you ever wanted to. But I've never heard of the wet plate camera. That's interesting. He uh and for a flash, he was using laden jars elimination from laden jars. This

is like the coolest camera ever. Yes, and cumbersome because you know, you don't really take this thing out to go take shots at the family on vacation. I'm out to the high school football game. Let me carry my laden jars and wet played carara with me. But I'm gonna need the team's help setting this up. But he didn't manage to get a readable photo of the newspaper at a shutter speed of one two of a second, well unexposure speed. Let's say that it actually used the

But you also probably remember Edward mind Bridge. I remember the name. Yes, yes, he had a famous experiment where um he had set up a series of cameras too because there was a challenge. Um. You may have heard of this guy, uh um Laden I'm sorry, yeah, I'm sorry. He may have heard of this guy. Leland Stanford he was the governor of California, and he was that that was the challenge was does a horse pick up all

four of its feet when it's running? And he was the one my bridge and a lot of people have seen this, UH seen this series of photos where they proved that the horse was picking up all four of its feet because he had a series of cameras and that the horse was tripping it as it ran by, and so each camera took photos a different a different way of doing it, but they captured a series of still photos because as the horse was running by, it took you know, each camera in turn took a still

photo and when you put them all together, you get essentially slow motion of this horse running. Yeah, and yes it does pick up all of its feet when we'll get it, and we'll get into that in a little bit, because of course the photography does lead into cinematography. But before we do, I, before we jump into that, I just want to mention one other kind because I did mention burst photography when we were first introducing this podcast, and that that John Fuller, Editor Extraordinaire UH wrote the

article on how burst photography works. First photography works on a similar principle of high speed photography. Now, with high speed photography, you may be talking about taking a single image and then setting up and taking another single image, right right, That's like I'm pointing, I'm pointing my camera at a hummingbird, and I take one photo. Right. The point of the high speed photography here is to capture

a very accurate still. Yeah, yeah, something that's going to be It's really used a lot in things like sports, you trying to capture capture that dramatic moment where the quarterback is releasing the hail Mary pass. I'm saying that right right, because I don't know anything about football or you know the people who absolutely positively have to have that shot of the water balloon after the balloon is broken and the water is still in the balloon shape,

but for the apple with the bullet through it. But clearly this sort of that has to happen, this sort of this sort of event is of course really hard to capture on film, not just because of the nature of the mechanics, where you know, you've got to have a camera with that proper shutter speed and film with that proper um photochemical reaction speed. You also have to have insane timing, and even by setting up an automated system where everything's going to happen automatically, you know, as

soon as the event happens that triggers the camera. Even that is really difficult to do. So perhaps what if you could have a camera that could shoot a series of photos in a very short amount of time using that same kind of a principle. Well, that's what burst photography is all about. These are cameras that have not just the really fast shutter speed and not just the special film that's going to to react quickly to a very brief exposure, but also the ability to advance film

rapidly as you're taking photos. So with a burst photography camera, it's pulling the film through very quickly, and the shutter is opening and closing, causing multiple exposures, but you're not not a double exposure because you're you know, the films being pulled through as you're as you're doing this, so that you can take a series of photos in a brief amount of time, So like in a second or two,

you might take dozens or more photos. And this way, Uh, the nice thing about this is that you can point your camera at whatever the event is and just start shooting photos until you're out of film and you have a better chance of capturing that iconic moment you're after as a photographer. Yeah, this is uh, this is one of those times if if you haven't really done a lot of work with people who are professional photographers, and you might be going. Well, last time I bought film,

I only had twenty four exposures on a roll. You can buy you know, if if you are interested in doing this, Uh, you can buy whole magazines of film and you know, attached them to the back of your camera where you have a very very long roll, or you can of course make your own, uh, if you're so inclined and are good in the dark. I used

to have to do. Actually, I was a newspaper report for a couple of years, and um, you know, we'd have a big roll of film and we'd load the magazines are are the cartridges ourselves And after a while you get pretty practiced at it. But the first few times, UH wasted some film. Um, but yeah, I mean so, so this is sort of one of those times when digital cameras sort of have an advantage because now that

we have bigger memory cards, and better digital photography. Um, the digital cameras are are so much easier and more cost effective uh than than film cameras in this regard. But the burst photography is amazing, especially if you are you know, it allows you to set up and have a much better shot at getting your shot than than

just just clicking and hoping that you got it. Yeah. Yeah, Well this kind of leads us, like I said, into cinematography, using film to capture images in motion where you are going to play it back so that you have the illusion of motions. So remember film as in like I'm going to the movies to watch a film is the the illusion of movement, and it works because we capture lots of images and then we put them in order and we uh we expose our eyeballs to those images

very in rapid succession, and that creates the illusion of movement. So, uh, the typical film projector will playback film at a rate of around twenty four frames per second, which means that every second that passes, you're looking at twenty four images. Twenty four photographs essentially is what that is. So you're looking at twenty four photographs in a row per second. And because of that, it sort of gives this. It gives this the illusion of the things that you're looking

at are really moving. It's not that you're looking at instances that are put together. It's like it feels like a flowing motion that has no no real interruption to it. I think it's interesting to note too that when you're you're saying twenty four frames per second, that's each frame is on a second. That seems pretty fast, But in my research on high speed photography, I saw mentions of one of a second. Um of course, that would take

a whole lot of film. Yeah, but you know, it's it's interesting to note that a second is reasonable enough to give us an idea of motion and to create that illusion for us. Before we conclude this classic episode of tech stuff, let's take another quick break to thank

our sponsor. So, if you have a projector that's going to play film back at a steady rate, so let's let's go with the frames per second, But you have a camera that can take that can actually expose film at a variable rate, that's where you can start playing with the slow motion or fast sped up motion on film. So, if you've ever watched an old movie, where for comic effect.

Usually characters start moving around really really quickly, you know, like there's a chase scene and suddenly everyone's running at a speed that doesn't really look natural. Well, the sack playing yakety sacks may very well be playing did and that's none of that, um, before I get sued and uh anyway, yeah, so this this is playing with taking more images per second and then playing it back at

a steady speed. Um. Now, in the old days, the good old days of filmmaking, I remember those days, you had cameras that were hand cranked, which meant that you had a camera man or camera woman really camera person, um turning a crank that was squirrels, possibly turning a crank at hopefully a fairly consistent speed for normal filming to advance the film through the camera as it's being exposed to light, and the idea being that you want to turn the camera at a good rate so that

when you're projecting it back through the projector it's a steady, smooth experience. So yeah, so this this camera is not automated. It it's it's manpowered, and people are known to be you know, imperfect, Yeah, not terribly consistent sometimes. Um so, yeah, if you turn the crank faster than normal, you'd be exposing more film in the same amount of time than you would if you were going at your normal rate, which and when when you're playing it back, remember you're

playing it back at a at a fixed rate. So if you've captured more images in that amount of time then normal, then you get the effect of slow motion, right, because while you've while you've captured maybe say, uh, you know, forty eight images and then uh you know, so you're looking at forty eight images over the space of a of two seconds. Um, if it were played back at normal speed, now you're looking at it at one second while everything starts to slow. Now, that could be distracting. Yeah,

so this is a that's over cranking. Yes, it's when you're cranking the camera faster than the projection playback speed. And there's also under cranking where you turn the crank slower than the projection speed. This causes a sort of the herky jerky fast motion stuff that you see, especially in older films, where people start to are moving faster than they normally could, and often it looks a little

jumpy because you're missing information. Right, the the the more amount of time you have between when two images are taken for something that's in motion, the less natural it's going to look when when you're playing it back right. Because so if I took a picture of Chris right now, and then three seconds later took another picture, and three seconds later took another picture, until I had you know, two D photos, and I played them back at a at a regular speed, uh, where it would look really

really jerky. You know, it wouldn't look natural at all, and jerky not just because of the subject matter, but ump bump, So it's only because I've been dried and cured. Right. So you may have heard of the term of speed ramping. Speed ramping is when you in the good old days it was done by accident, but today we do it on purpose. Speed ramping is when you change the capture rate of uh the film or video during a shoot. And this is where you get those weird effects where

like it's often done in action sequences. For example, let's say it's a fist fight between two characters and it starts out normal, and one character starts to throw a punch, and just as the characters throwing a punch, it switches so it goes into slow motion, and then just as the punch makes contact with the other person, it speeds up again and it changes, uh, the the capture rate, but the playback rate remains constant. That's what we call

speed ramping. And there's certain directors who are infamous for speed ramping. Um. Just you know, if you ever have seen the movie three hundred or Watchmen, you know one of the ones I'm talking about use a speed ramping so much that it's distracting at times for some people. Other people love it. I personally think a little goes

a long way. I'm sorry what anyway, that they're all based on the same principle, the fact that if you keep the playback rate steady and you change the capture rate, you can you can make film appear to move slower or faster. Um. Now, you could also play with the playback rate. If you kept the capture rate the same and you change the playback rate, you would get the same effect, right you would. You would either try and display more images per second or fewer images per second

than normal, and you can get the same fact. This is a lot easier to do in video than it is in film. Sure, sure, but it's funny to note again that like so many other things in photography, that the key to slow motion is high speed photography. UM To to really get an idea of what's happening and slow it down, you have to capture many images so that you can you can go from image to image at a slower rate and really get a good idea of of the motion and how things are transpiring, uh

in that image. Yeah. Yeah. If you if you take an uh a video of something or a film of something, and it's at eight thousand frames per second and you play it back on a twenty four frames per second projector, it's going to take you a long time to get through. Like even if you only shot for maybe five seconds, you know that's gonna take you a long time to get through those five seconds when you're playing it back

at a rate of twenty four frames per seconds. So then you get this incredible slow motion effect where at times it may look like nothing is even moving because everything is. You know, you're capturing such tiny moments of time that it's hard for us to detect changes until

they are dramatic changes. And this is where you can you can see some of those really cool effects, where like Chris was saying, the water balloon where you pop the balloon and the water has retained the balloon shape for a couple of a couple of split seconds, like moments in time, and then you start to see it, you know, of course fall uh that that's We've seen some really cool footage because of the this uh this technique, and you can too if you go to the house

stuff works dot com site. We have a lot of clips from the Discovery show time warp Um, which was was really popular a couple of years ago because it showed extreme slow motion. Yeah, using amazing high definition slow motion cameras. They are taking thousands of frames of footage per second and then playing it back at normal speed. Yeah, and it's just it's absolutely amazing. I and I can watch them all the time, you know, even the ones

I've seen before, you know, I can. I can go back and watch them just because it's so fascinating how how well that works. I love the ones where people get slapped and you just see the face deform slowly. Wow, that's what happens. Whenever I say anything to anyone that's insane, I'm constantly can't Yeah, my face is hurting. I got slapped just before this podcast. Actually, yeah, but it was you that did it anyhow. I never said that it

was necessarily caused by someone else. That's true, that's true. But yeah, I mean you can you can uh, you can see that right now. They're they're still up there. And I think when we post this will probably I'm pretty sure there's a playlist we can we can show people. Yeah, um, yeah, that just it's just a lot of fun to do that. And it's a lot of fun to to fool around with high speed photography just as that, you know, just as somebody who is a hobbyist, um, to see what

you can do with it. And now, granted, if you want to get like a really good high speed camera, this can be an expensive hobby. Yeah, I mean, if you're talking about the top of the line uh kind of set up, then you're you're looking at thousands of dollars. So it's not a cheap hobby necessarily, but it is really it's really cool. Now and then you know, if you're if you're really staging things too, um, yeah, of course,

then you have got the whole staging costs and stuff. Yeah, and you're starting to talk about again, because it is a matter of uh, the camera detecting the image and and getting synchronized with the the event that you're trying to photograph, and um, you know you have to buy the equipment to do that. We were talking about sound equipment. They are setups that require you know that that the sound will cause the the camera to fire. And you know this is again you're having to buy more gear. Um,

but it's it's it's fun. You can if you can afford it. It's pretty pretty interesting stuff. So yeah, this wraps up our discussion about high speed photography, slow motion cameras in general. Film. Uh stuff is really really interesting. In fact, it's so interesting to me that when I

look at the complexity of these devices. I mean, the principle is pretty simple from a high concept point of view, but when I started looking at the ingenuity that was required to bring a camera into reality, Uh, I just it's phenomenal to me. Again, It's one of those things where we take it for granted now because they're everywhere. I mean, we have cameras incorporated into practically every mobile

device you could think of. But the principles behind it and It's just it's just phenomenal amazing that we figured this out. Yeah, I mean think aboy, we I mean people way smarter than I am. Well, you think about how the difference in the early cameras that you know, de guaro types and and the wet plate type devices versus the tiny little cameras in our smartphones, you know, shoes and everything else. I don't want any shoe cameras well.

That wraps up this classic episode of tech Stuff. I hope you guys enjoyed this trip back in time where Chris Pallett and I looked at slow motion film and high speed photography. It was a lot of fun to go back and revisit that. I'm actually enjoying going through the archives and picking out episodes for you guys to listen to, stuff that you probably haven't heard unless you are a long time listener. If you guys have any suggestions for future episodes of tech Stuff, send me a message.

The email address is tech Stuff at how stuff works dot com. Or drop me a line on Facebook or Twitter they handle it both of those is tech Stuff H s W. Don't forget to follow us on Instagram and I'll talk to you again really soon. For more on this and thousands of other topics, visit how stuff works dot com.