Lighting 101: Flash Sync Speeds
Basic flash sync speeds, and just to talk about first, for most people have DSLRs or mirrorless cameras that are similar to how DSLRs work. Most people have cameras that have an actual shutter mechanism built into the camera. This first slide, and these slides were built by Elinchrome for an article we did last year, and they're super awesome, because they really show very succinctly how the shutter works and how it works syncing with the flash. So we're not even talking about flash yet. We're talking about just how the camera works, and so you see over and over in this slide, at 1/200th of a second, so what we're looking at here, this is the flash curve, so this is the burst of light to you know, its highest light output and then how it tails off. And then that's your shutter over there going through the camera, and in modern cameras, it's a two-piece focal plane shutter. So you see at 1/200th of a second there's a split moment where the entire shutter, or the entire sensor is exposed...
behind the shutter. You guys see that okay there? That's critical because that's your sync speed for your flash. That's why your flash syncs it. If you're a Canon, it's 1/200th of a second. If you're a Nikon, it's 1/250th of a second, or 1/320th of a second depending on which camera you have. That is the highest shutter speed at which the sensor is exposed fully at any one given moment. And so that's how, technically, flashes sync. If you have a longer shutter speed than this, then your sensor is exposed for a full second or whatever your shutter speed is, so that's not an issue. But what happens when you go to higher shutter speeds like 1/600th of second? You see at this point that the first curtain drops and then the second curtain starts almost immediately and then there's this little slit moving down over the sensor. And if we go to an even higher shutter speed of say like a thousandth of a second, there's just a little slit going down the sensor, and it gets even smaller at like 8,000th of a second. That slit is super thin, just fwwwt, drops. So the first curtain and the second curtain are dropping at the same time, which is why if you try to go beyond your flash sync speed with a speed light or any strobe, you get these black bars on the image. And we'll talk about that in just a minute. So, let's move on to medium format leaf shutters, just still talking about the cameras, and how this works. There's Hasselblad, there's Phase One, there's Fuji now. There's been a bunch of medium format cameras over the years that have incorporated leaf shutters. Hasselblad is well known for their leaf shutters, so I used some images from them. So the shutter is actually built into the lens. It's not in the camera body, and the difference with leaf shutters is that they're circular, so it closes down like your eye blinking with the shutter closing in on all sides, and it may have more blades than this, but because it closes down and opens like that, there's not a slit moving over the sensor and that allows these to sync at every shutter speed that the camera has. So like on my Hasselblad H5D, it has shutter speeds up to 1/800th of a second, which is not that high considering our cameras go to 1/8000th of a second. The new Hasselblads go up to 1/2000th of a second. I think the Phase Ones have 1/1600th of a second. It depends on which camera you have. But that means you can sync with a flash up to that shutter speed. You know, it doesn't matter where you are on the shutter speed of the camera. All shutter speeds sync with the flash, so while medium format cameras are fairly expensive, they offer something that you don't get with 35-millimeter DSLRs. The other thing to note is that you're using the entire flash burst. You're not using a slice of the flash burst. We'll talk about that here soon. So, as we've already talked about, the flash sync is just how the camera synchronizes, and it's how it synchronizes with that flash burst, because we're gonna talk about next, just after this next slide, is flash durations and how long that burst of light actually lasts. So as we talked about earlier, at 1/200th of a second the entire image is lit. At 1/400th of a second, on any camera that I know of, besides medium format, what's happening here is you're actually imaging the back of that rear curtain as it drops over the sensor. So while your flash is still illuminating this, your rear curtain is coming up and blocking the light from hitting the sensor. And it's reversed, so if they're dropping from the top, remember the image is inverted from what you're actually seeing through the viewfinder. And at 1/1000th of a second, it's moving so fast that you're barely lighting anything. So if you're going past your normal sync speeds, this is what you're gonna see. So flash duration. Now, this is key to this whole enchilada here. And I created this chart, which, there's many versions of this chart, just to explain the definition of what a flash duration is. So the blue line here is the burst of flash, so this is intensity or amplitude of the flash, like how much light is being thrown off, and this is time, so I mean, the original flashes were flash powder, and you just lit up this magnesium powder and poof, you got this light, and these flashes these days are xenon gas for the most part inside of the flash tube. And it's still no different than the magnesium powder. We're just using electricity to ignite this xenon gas to emit photons or light. But there's a time on that. It's not like it's instantaneous every single flash, and as you turn the power up or down, the flash duration will change for your flash. So, how do we measure the flash duration? Most companies use what's called a T0.5 flash duration, and that is the number where 50% or where the flash duration output or the flash output is above 50% of the output. So does that make sense? So it's a very short period here, and they don't count the rest of this tail, and this is an approximation of a flash curve. It may not actually look like this depending on the flash, the company, how they've engineered their flash. There's also what's known as a T. flash duration, and that's a little more representative of like the real world actual flash duration because as you can see, it's the time that the flash amplitude is above 10%. So you can see that's a longer period of time, but it's closer to the actual length of the actual flash output. So typically we'll probably be talking a T.5, 'cause that's the industry standard, and that's what most of the manufacturers use. Braun Color typically uses T.1, which is more accurate. Pretty much everybody else uses T.5. So if you're looking at different flashes out there on the market, it can be difficult sometimes to tell what their numbers mean, because they might be quoting T.1 for this brand and this other brand says T.5. So you have to kind of translate and there is no formula for translating. Like T.1 is not just always a third of T.5. So unless they measure it you don't really know. The good news is there are light meters now, like this brand new Sekonic. It's their brand new Speedmaster. I don't even know if it's on the market yet, but it can actually tell you the exact flash durations you're getting out of your flashes. So, and we'll be talking about flash durations a lot in this class because that's part of this whole advanced lighting. So just to further explain flash duration, this is my road bike in my living room, and I just wound up the wheel and let it go super fast. And then I measured the flash duration. These are T.5 as you can see right here, so this is 1/363rd of a second. So that's a really slow flash duration. Just like a shutter speed, you know, if I start shaking my camera at 250th of a second and take a picture, I'm probably gonna get a blurry picture. So you see the wheel is fully blurred. If I turn up the flash or use a different flash head, so this is 1/5350th of a second, you see the wheel is stopped and it's because I had the lights on, like right here in the studio when I was doing this, that you see just a little bit of motion blur. It's 'cause I was shooting at 250th of a second and so at 250th of a second with the lights on it's impossible to take out all motion blur, because you still have the 250th of a second. You know, even though your flash is really fast, your 250th of a second is still really long compared to that flash burst. If I would have turned out the lights, there would be nothing but super crisp detail on that, and so if you're in a studio, you turn the lights down when you're using a really fast flash duration, then you can freeze motion completely, especially if you have a black background. But that just gives you an idea of the stopping power of the flash, which is, you know, historically when you went to go look at flashes, that was the number you looked at, like how fast is this flash duration? Some numbers, you know, I think like Profoto is down to 1/25,000th of a second. Braun Color's at 1/20,000th of a second. I think the new Pro 10 from Profoto, it's something like 1/80,000th of a second. It's some insanely amazing number. But realize your speed lights actually. This is where speed lights can come in handy. If you look in your manual for speed lights, it has incredible flash durations, like down to 1/30,000th, 1/45,000th of a second at some power settings on the speed lights, at least for my Nikons. I looked that up 'cause I was like wow, that's incredible, so if you need wicked fast flash durations, pull out your speed light and see what that's got 'cause that might be useful if you need a really fast flash duration. So, just as an example, here's a kayaking image. You notice I shot this at 250th of a second, so this is normal flash sync speeds. This was in the shade, or just before it got dark, and I'm at f/5.6-ISO 160, so typically I'm at low shutter or low ISO settings. We're using normal flash. This is all flash duration. This is my ranger pack with the action head. I think at full power it shoots, I think the flash duration's like 1/2600th of a second. So that is the flash duration stopping the motion of the water. There's still some little parts that aren't fully frozen, but that's totally fine. That shows a little bit of the motion. That's another reason why I use the Elinchromes and why a lot of sports photographers use the Elinchromes because they're different than Profoto and Braun Color and some other manufacturers in that they have their faster flash durations at the highest power settings. You know, if you have a flash duration that's 20,000th of a second at the lowest power setting, that's not gonna do me a whole lot of good if I need to put my flash 20 feet away from the subject. So just to give you some examples of how flash duration works, this is a really fast flash duration with a really slow shutter speed. So I'm at a 20th of a second, so you see there's motion blur. You see the motion blur of the rider after the flash went off, but the flash is stopping his motion and creating crisp lighting on him, so you can actually see him. And I love doing this. I've done this for a long time, you know, using flash just to stop the motion, but then allowing the shutter to show the motion of the rider.
A question had come in from Joey, and this was on the photo of the kayaker.
Uh-huh, I'll go back.
That sort of showed us some harsh shadows from the long throw reflectors. Is there any way to soften that light and still get distance, or is that kinda the nature of--
There is. I could just put a softbox on that that's bigger, like we talked about earlier, and that would somewhat soften the shadows. I think the next section we're actually gonna talk about hard and soft light a little bit, but you know, that is when you're-- The farther away you put your light, the more it becomes a point source of light like the sun, and the more you get hard shadows. It gets difficult to take those hard shadows out, or you set up another light. Like I could have set up-- This strobe was coming into him from this angle. If I set up a strobe back here to fill in those shadows, I could have minimized them, but then I also flatten out the image, because I'm eliminating shadows. So, there's a catch- here and it's tough. If you use a bigger softbox and you diffuse the light, that means you need to have way more flash power. And this was shot with normal flash techniques, so I'll show you some images where we've been able to overcome the hard lighting because we can use the high sync or the hyper-sync.
So in a setup like this, I'm guessing was this a rehearsed point where you asked him to do a turn, or like how do you kind of choreograph the shot so that you have your lighting set up for when there's gonna be a almost roll?
Yeah, exactly, so this is-- That's a great question, 'cause that sets this image up and I didn't explain that part. This is what's called a surf spot in kayaking, so he's sitting there doing these flips continually. So it's not like I'm waiting for a kayaker to come down the river and do something right here. I would be there for many days if that was the case. And then because the lighting has to be very specific, you see the foreground's not lit, the background's not lit. It's just hitting him, so I know he's-- We were there for 2 1/2 hours. So that helps. And I could have put a light on the other side of the river. I would have had to have him take it over or jump in a kayak myself to set that up. But typically a lot of the lit shots for adventure sports are gonna be one to two lights maximum, because your subject has to move and we'll talk about that as well.