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Shutter Systems

So, shutter systems. There are different cameras that are classified by the type of shutter they use in the camera. And the system that most of us are not gonna encounter and not use is what's called a "leaf shutter system." And this is what is actually used in the point-and-shoots. And so, this is the most common world, but it is also used in some medium-format cameras as well as some large-format cameras. And this leaf shutter system is called this because the shutter actually looks kinda like a leaf from a tree. And the shutter is a very simple system. It just kinda spreads apart, opens, lets light in, and then it shuts. And it's something that is installed in the lens, whereas the focal plane shutter is at the focal plane, all right? And so, the leaf shutter system works like this if we look at it sideways. And it's kind of interesting all the work that a little point-and-shoot needs to go through. So, as you turn your camera on, light comes into the sensor and you see what's going...

on on the back screen. Now, the shutter system is gonna be built into the lens, as I said. And when it's time to take a photo, what the camera needs to do is it needs to shut the shutter, prepare the sensor to capture the image, the shutter then opens for that particular shutter speed letting light in, and then it needs to block that light off again, and then it needs to open again so that you can see the image. And so, it needs to close, open, close, open every time you take a single photo. So, there's a lot of work that that shutter needs to do. But luckily it can move very, very quickly and it doesn't have a very large space to cover. So that's how it works in a point-and-shoot camera. So, it's a very simple system. It's quiet with very low vibrations, so you're not gonna be shaking in the camera. And one of the neat things, and this is one of the reasons why medium-format and studio photographers like this system, is flash synchronization can be used at all shutter speeds, which is very handy for controlling light. And we'll talk more about that in the lighting section. The disadvantage of this is that it's not capable of really high speed shutters, like 1/8000th of a second. It kinda has an upper limit, usually around a thousandth of a second. And so that does make it harder to use in certain types of lighting situations. You need to get a shutter in every lens. And so, now, every time you buy a lens, you're buying a whole shutter mechanism that is in that lens. And that's gonna add to the cost of the lens, the complexity of the lens, and it's gonna make them a little bit more expensive, because they now have to design all these lens elements, "Okay, here's where everything needs to be. We gotta put a shutter system in there! Ah, darn it! Now we gotta move all these lenses, and now we're gonna have to compromise various aspects of the lens," when that happens. And so, it's not real common on the interchangeable lens cameras, but it is out there. And I just kinda wanted to get that one out of the way before we get to the biggie here. This is the focal plane shutter. This is what is in most of our cameras that we are using if you have an interchangeable lens camera. So, the SLR camera has the mirror that's bouncing the light upwards. We get the mirror up and out of the way so that light can go back to the image sensor. Now before it gets back there, we have to get past the shutter unit. And the "shutter curtain." as it used to be called, because it was actually a cloth curtain, but now it's four metal blades, is gonna have a first curtain and a second curtain. So, the first curtain is blocking the light and what's gonna happen is when it's time, it's gonna slide away, light's gonna come in, and that is your exposure, and then the second shutter is gonna go ahead and drop down and close off. And then the whole system will reset back to the starting position. And it does this so every pixel is exposed for exactly the same amount of time no matter where it is on the sensor. And then, once it resets, the mirror will go back down and the whole system will reset. Now, one of the things that happens at very fast shutter speeds is that the second curtain will... start to close right after the first curtain has started its movement. And so, as you can see here, and I think I'll do it one more time for you, it is essentially scanning the image on the sensor. And so for very fast shutter speeds, that difference between the first and the second curtain is very, very small. So, it is scanning the image as it moves across. Now, you might think that this would affect subjects that move very quickly, and it is possible, but it's just not something that we're gonna see because it happens so very, very quickly. But that is what's happening and how very high shutter speeds can be done. And this is one of the thin%gs that we're gonna kinda come back and talk again when we get into the world of flash photography. So, in the lighting section, about halfway through it, when we introduce flash, that aspect will become very important to that topic. So with the focal plane shutter, this is a proven technology that has been working really well, and all the kinks have been really figured out. So it's a safe system to go with. We can get to some very fast shutter speeds and we don't have shutters in the lenses, so it simplifies and gives us a wider variety of lenses that we can make more simply. Disadvantage on this system is that it is limited on how fast we can work with flash light with this. And so if you wanna add light, it has some limitations. We'll talk, as I say, more about that in the lighting section. That shutter opening and closing is going to have a little bit of vibration. Not as much as the mirror moving up and down, but that shutter is a little bit of a klink every time it opens and closes, and might be enough to cause some blur. And another disadvantage is the very fast frame rates. Now, as I said, I think we can go up to 14 frames a second, and I think there was another camera that did 15 frames a second at one point. But this is a lot of mechanical movement, 15 frames a second, going back and forth. And so if we want to shoot movie speed, at 30 frames a second or 60 frames a second, which we may want to do, potentially in the future, for sports and action, that's gonna be a limitation of this system. For most of us, for general activity, it's not that big a deal. Now the way the focal plane shutter works on a mirrorless camera is slightly different. And we got a hint of this back with the leaf shutter system here. So, on a mirrorless camera, you turn it on, you get to see what the camera's pointed at. That means the shutter is not blocking the sensor, okay? So let's take a look at what happens at the sensor level when you are going to take a photo. Now these cameras, like the SLRs, have two shutter curtains that work very similar, but a little bit different. In this case, they have to start in the open position, because that's where your camera is when you just turn it on and you wanna compose your image. When it's time to take a photo, the first curtain will close, and then it will open, now you're taking the photo, and then the second curtain will close. And so, it's got to be open, and then it closes, it opens, it closes, and then it opens again. And so it's gotta work pretty hard. There's a lot of opening and closing of these doors in order for things to happen. And so if we were to look at the sensor from the front, we've got our shutter unit on the top, we've got our shutter unit on the bottom. Let's take a photo. Let's close it first. Now we're taking the photo. And when that first shutter curtain opens, there's a little bit of vibration because it's opening up so quickly, it's like slamming a door shut or slamming a door open. It's going to cause some vibrations. And that may affect picture quality. And then it's time to close the second curtain and that's the end of the shutter. And so, that first shutter movement may cause a problem. And so one of the options on cameras these days is what's called an "electronic shutter." And there's a lot of SLRs that will have this as an option. Now the electronic shutter is not nearly as exciting for me to graphically show you. It turns on, it turns off. But what it is doing, it is essentially opening, and then it waits for a moment for this to dissipate that movement. And then it basically turns the pixels on and off starting the exposure. And so this is how an electronic shutter can work. Now, the problem is that you're not recording all the pixels at exactly the same time. So on a single lens reflex, for instance, a typical Canon SLR, a Nikon D810, they will have something that's called an "electronic front curtain shutter." And so this is where the front shutter curtain is electronic in nature, and they don't use the physical one. And so what happens here is that they basically just turn all the pixels on and then use the second curtain to stop the exposure. And this eliminates the bouncing of that first curtain, which means there is no movement before the picture is taken, which means you camera is perfectly still. And if somebody was into super telephoto photography, or high-magnification macro photography, where their camera's on a tripod, and any sort of movement would cause a problem, this is a way to get around that movement problem. And so future cameras are gonna just ditch these shutter units completely. At this point in time, there is no significant camera, I would say, out on the market that uses purely an electronic shutter, where its simply turns the pixel on and turns it off. And the technology is getting faster and faster and faster. And what we need to be able to do is to turn all the pixels on and all of them off at exactly the same time. And right now, we don't know how to do that, so we do this scanning process. And it works pretty good for some situations, because we've got that scanning process pretty quick. But as you pan the camera and the position changes, as you are moving from pixel to pixel... I shot a grid in my studio, and this is what happened with a perfect grid system as I panned the camera from side to side. Now as I did the same thing that on the street as a car drove down the street, you'll notice those buildings don't look quite right, okay? And that's because it's scanning one line and then going to the next line. If I set the camera perfectly still on a tripod, and I let a bicyclist ride by, those wheels don't look quite round, all right? And that's because they have moved as that sensor has scanned different lines going up and down that sensor. And so, for action photography, these electronic sensors don't work too well, these electronic shutters. They work perfectly fine if your subject's not moving. And so you have to be very careful about movement if your camera has this option on it. Does your camera have this option? Well I don't know. It depends on what camera you have. And so, a variety of cameras, like the Sony camera here, this is the a7R Mark II, one of the more capable popular cameras right now, it's got a full mechanical shutter in here that I can use, or I can use an electronic first curtain, and that's going to reduce the noise level, reduce the vibration level, or I can use a fully electronic shutter, but then I start getting into some of these problems. And so, I have three different modes that I can set it on on this mirrorless camera. And so it really varies from camera to camera as to what you can do. So, the electronic shutter, no vibrations, I love that. The fact that it is perfectly silent is very, very cool. There have been times in travel photography where I'm wanting to be really, really quiet. I'm in a church or a mosque or I'm in a playhouse and I don't want to make any noise. These shutters are perfectly silent. Now the disadvantage to these sort of systems is those moving objects are distorted because of our current scanning system, the way that it works. Another problem is limited flash synchronization, especially with that scanning, we have to have all the pixels turned on at the same time if we're recording flash at the same time. And there's no satisfying click of that shutter. One of the things that people, like the users, love is their cameras make a really good click. And6 it's one of the lower priorities when buying a camera. But having a nice click, it just feels like you did something right. And that's why a lot of phones and little compact cameras put in those electronic ones. And I haven't heard any electronic ones that have that same feel. And maybe it's because there's no movement and they don't have any feel to them. It's just all sound. And so, at some point in the future, we're going to think back, "You remember when cameras made that click noise? (laughter) Why was that? I wonder, why did they make a click noise?" That is a question that is student will ask in a photography class in the future. "Why did cameras make a click noise? "What's going on inside?" So that's the future of photography, I'm absolutely convinced of it. It's gonna save money. It will make things better, but we just need to jump over a few technological barriers.