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Artificial Light

Alright, so now we are officially adding on some artificial light. Time to get those flash units out of the camera bags, power 'em up, and get 'em firing. Before we get into this, let's talk about some of the fundamentals of how flash works and exactly what's going on. And so, let's go old-school here, let's just start really simple flash. Back in the old days, there were flash units that, basically, this was their whole control system. Off and on. Alright? You want flash or no flash? That's all it did. And what it did is it fired off a bunch of light and that light hit our subject and bounced back to our cameras, and if it wasn't enough light, you had two options. You could move the camera closer or you could move the person closer to the camera. Those are your only controls. And a lot of times you didn't know about this until after you had shot the photo and developed it, because you were shooting film. And, so, the other option that you could do, of course, is you could change your ...

aperture. And, so, oftentimes what would happen is they would have scales. If you fire the flash, at this aperture, your subject could be this distance. And so you'd say oh, okay, this I need 5/6, and then I move here, and I can be at F8. And so, you would have these different scales that were on the back of flashes. The next advent was adding some control to the flash, where they were actually able to control how much power, how much light came out of that flash unit. And you could dial it down to half-power, or quarter-power, or one-eighth power. So now that gave you a little bit of flexibility because now you had control over how much light was coming out of your flash unit. And then automatic flash was invented. And, so, in the automatic flash, the way it worked is that inside the flash unit itself, there was a light sensor that was determining the amount of light bouncing off of your subject. So, your camera's flash would fire, light would hit the subject, bounce back to the sensor, and the sensor would try to determine whether that was enough light for that subject or not. And if it wasn't enough light, it would continue firing the flash until it did have enough light. The problem was, is that if your flash unit was looking at a different scene than your camera was, so, for instance, you had a telephoto lens, but your flash is firing out all over the room. The amount of light getting reflected back to your lens was not a very good representation of what you were taking a photograph of. And it would often overexpose the subject that you were shooting at. It wasn't very accurate. In some situations, it was pretty accurate, but there was a lot of situations where it gave you very poor results. So the next step in technology was something called through the lens flash technology. Now, rather than having the sensor in the flash unit, that was checking the exposure, they had the actual lens doing it. And the way modern cameras work with this, is just before the picture is taken, it sends out a test flash, which hits the subject, bounces back to the lens, and then the computer in your camera and flash system determines if that was too much or too little light, and then the camera will actually take the real picture. Now, it does this in microseconds as you press the shutter release. And so, if you've noticed, when you fire a flash picture, and you have a real sensitive eye, you'll notice there seems to be a series of flashes. And sometimes what will happen is the flash will send out a signal, it'll test it, it comes back, and it's like that didn't work out. And they send another test, and then they send another test, and then they kinda finally have it narrowed out and then the actual flash fires, and it all does this in a blink of an eye. Happens really, really quickly. Another little piece of technology that you need to understand about when it comes to flash is the inverse-square law. So, what this law states is that light traveling twice the distance has one-quarter the power. This is really important, because when we talk about how far away can you be from your subject with a flash unit, this comes into play very heavily. So, let's take our flash, and we fire the flash for a certain amount of power. And it's set right here. Now, if we want to go twice the distance, let's think about what happens, that light spreads out horizontally and vertically, twice the width, twice the height. And so now what happens is it has one quarter the power, because it is taking up four times the area. And so, four times the area, one quarter the light, light traveling twice the distance, has one quarter the power. So there is a big fall-off in light. This is what we talk off. Light fall-off. It falls off very quickly. It diminishes in power very quickly. So, if we are firing at these two different distances, we can still fire the flash at the same power. But we can make an adjustment with our aperture. So we're gonna need to open up two apertures. If we need f5/6 at the first setting, we double that distance. We're gonna need to open up to 2.8 to get an equal exposure. So, if you're working with manual flashes, this is what you would manually adjust on your flash. Now, it depends on if you work with manual or automatic. And there's reasons for doing each. I've worked with automatic flash and the TTL system, which works really good, especially in situations that are changing very quickly, but when you are in a studio situation, or you're doing a portrait, where you're set up, and you have really good control over the situation, you're gonna be working with a model or a group of people, or whatever subject you are, and you go, well, we're gonna be here for 10 minutes, and I wanna set this up ahead of time, I'm gonna get things set right. When you set things up manually, ahead of time, you can be sure that it's gonna be consistent, which is really nice for a lot of situations. This is a great photo to show the example of light fallout. And so, I've got my buddy here, holding a flash. He fires the flash, what does it illuminate? Things directly in front of him, like five, 10 feet in front of him. How much flash do you think is reaching the top of the mountain there? Not much. It is not doing much in the illumination. In fact, if you were to stand 20 yards away, there's not much flash out there. And so flash will illuminate things that are directly in front of you. And so, if you are planning to use flash, it is things that you can probably talk to. Things within talking distance. If it is further than talking distance, your flash will probably not reach it, unless you are using some very special type of flash. Alright, lets jump into your camera. Your camera sensor, and the focal plane shutter, which is what virtually all of our cameras are using. You'll recall back from the shutter speed section that we have two curtains. We have the first curtain and we have the second curtain. The way flash fires, what's triggered in your camera, is that your camera says I will fire the flash as soon as the first curtain is open. So, let's go ahead and open the first curtain, and as soon as it's open, it'll then fire the flash. So this is how a normal shutter speed works. I'm ahead of myself on one slide, let's add flash in now. Oh, so I'm discussing the shutter speeds here. So remember at fast shutter speeds, the entire imagery is not visible. What happens is that it's kind of a moving slit that it is scanning your images in on. And so that's gonna be tricky when it comes to adding flash to it. So, on very fast shutter speeds, it's a very narrow slit. Alright, so here's with flash synchronization. Let's open the first shutter, and as soon as it's open, is when the flash fires. Because we have to have the entire image sensor visible to the light when that flash fires, 'cause it fires for just a fraction of a second. And then the second curtain will come down, according to whatever shutter speed you have set on your camera. And so if you were to set a really high shutter speed, and then fire the flash, you would end up with a result like this. And those of you who had cameras back in, maybe, the 70s and 80s and 90s, where you had to manually set things, I know a lot of you made this mistake. Because I saw a lot of photos where the shutter was partially closed, and part of the image was illuminated, very bright, and part of it extremely dark. And that's because the second shutter curtain was coming down. Modern days, we don't have this problem because the cameras will not allow the flash to fire when the shutter is closing like this. The flash won't fire, well, actually, what will happen is the camera won't allow you to set a high shutter speed if the flash is turned on. So, if we could measure the time within one-thirtieth of a second here, when you fire the flash, here's what happens. And the power is gonna be listed on the left-hand side. So let's fire a flash. This is a relatively low-powered flash. It fires all of its light right at the very beginning, and then it doesn't do anything for the last 90% of that time. And if we were to crank up the power on the flash to make it more of a medium-powered flash, the only difference is that the flash lasts a little bit longer. It's basically a light that's turned on, for a little bit longer period of time. And then a high-powered flash, well, it's just a little bit longer period of time, but, for the most part, it fires very, very quickly right at the beginning of that opportunity for firing the flash. Usually, that's happening at about 1/1,000th of a second. Now, do you remember back to the shutter speeds? What type of shutter speeds stopped fast human action? It's about a 500th of a second or faster. And, so, when we fire a flash, it is gonna stop virtually all fast human action. It's fast enough on its own. It doesn't matter what shutter speed is happening, it's just the fact that that flash is firing. It's stopping action that moves very, very quickly. Now, the actual flash duration, these are all estimates that I have up onscreen right now, 4,000, 2,000, 1,000, it's gonna depend on the actual flash unit you have. Some units are designed to fire even faster than that. Some are a little bit slower that this. This is an estimate. So, if you have a flash set to a high-powered flash setting, and the flash is firing at 1/1,000th of a second, where it's really in that quick area, we can use a variety of shutter speeds. And these shutter speeds have no impact on the power of the flash, alright? So if I go from 1/25th down to 2/50th of a second, I haven't affected the power of the flash at all. So shutter speeds have very little control with the flash. They're almost completely independent controls. And so, your shutter speed does not effect the power of the flash. What effects the flash is the intensity that it's set at, and the actual flash duration, which is something that we often don't have specific control of. Another little technical aspect we need to be aware of is red eye. This was a problem for a long, long time in photography. And this is where your subject has light illuminating off the retina off the back of their eye, and it comes out through their pupil, and you see this as red eye. Pets also get this as well, but sometimes it's different colors. What's happening, on a technical scale, is that as the light fires, it goes through the pupil, it hits the retina in the back of the eye, and that will be seen if it's lined up with the lens, where the camera is. And so if the flash and the lens are very close together, you're likely to get this red eye, because these two angles are so very close. Now, there are two basic ways that you can reduce red eye. And so, one way is that you can fire multiple lights of flash, and what that will do is that'll change the pupil size, it will constrict the pupil size and make it smaller. And, so, in this case, let's make that pupil size smaller and if we shine the light in, it's gonna be a smaller area on the retina, and a smaller area for us to see. The other way for us to reduce red eye is by moving the flash off the camera. By doing this, we're gonna be illuminating a different area within the retina, it's not gonna be visible to us when we shoot the photo. And this is the preferred system for most photographers. The system where it fires a bunch of flashes I call 'em the disco flashes, 'cause there's nice little strobing lights, is really annoying for subjects. And where you often have a lot of red eye is in kids. Kids have a lot of red eye. And when you fire a bright, blinking flash, that might be disturbing, but, you know, a lot of kids will think that's the photo, and then they'll turn away, and they'll go off on to their next thing, and you're gonna really miss the moment 'cause you press the shutter release, and it goes pop-pop-pop-pop-pop-pop, pop. And it waits. And so you've lost that two seconds when you're trying to time the shot. So it's terrible for timing the shot. And, if you do get red eye, well first option is get the flash off the camera. The second option is you can just fix red eye in post. So easy in Photoshop, Lightroom, and other programs, that, if you do get it, it's not the worst thing in the world because it can be fixed fairly easily.