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Expand your lighting options and get the most out of your flash as photographer and teacher Brent Winebrenner takes a practical, hands-on look at the theory behind exposure, with a special emphasis on electronic flash exposure.
Even with today's automatic flash systems, there are good reasons to understand how flash exposure really works. Brent details these concepts in this course. The course describes how to calculate the true power of your flash and how to modify its output to match your needs, a technique that can extend battery life, reduce recycle time, and provide exposure control that is more predictable than fully automatic modes. The course concludes with several shooting scenarios during which Brent explores the creative use of gels, reflectors, and other light modifiers.
For our second shoot, we've just moved over a little bit from the scene featuring the industrial tubing to kind of an urban outdoor setting that we've created, and what I have in mind for this is to put some dramatic lights into the room behind the model and then also then light her with a normal exposure and try to emulate a street light coming down from overhead. So the objective is again to get a normal exposure on the model, create some drama in the background and then ideally create kind of a little bit of an accent light with this overhead street lamp. So here we go. Okay, Savannah, you can just hang out on that mark.
I'm just going to take an exposure to see what the overall lighting looks like. The light on you is perfect, but we've got a big hotspot on the left-hand side of the frame. So, Lauren, I still want to shoot at f/8, because she is going to be moving through that frame so I need the depth of field. So when I had the flash 11 feet from the model, I got this pretty bright hotspot in the upper left-hand corner, and I wanted to try to eliminate that, and one thing that I could have done would have been to place a screen or some netting, diffusion material between the flash in that hotspot to kick that value back down, but they didn't have any on the set that would work.
All the diffusion flats that I had had hard edges that would have cast a noticeable shadow. So the next place I went with this was to move the flash back from 11 feet to 22 which will help me more evenly illuminate the background from the right-hand side to the left-hand side. Then I've asked Lauren to cheat or feather the flash, aim it beyond the center point so that the fall-off from the flash occurred on the left side of the frame.
By doing those two things, moving the flash back and feathering it past the center point, I was able to more evenly illuminate the background, and I did that while maintaining normal exposure on the model by opening up the lens to compensate. We made a two-stop change by doubling the distance. So we should be good to go. All right, big smile. All right, we're getting close. So the problem we're dealing with is that the flash to subject distance on the left-hand side of the wall is quite a bit closer than it is on the right-hand side.
So what we need to do is just keep cheating that light up, but the light on her is perfect. Now what we're going to do, Lauren, is get this light going on the backroom here. Lauren: All right. Brent: So, I've set these grates up, because I want to throw a pattern across this wall to give it a little more visual variety, and what I also want to do is underexpose the wall by a couple of stops. So I was in here earlier, and I measured 16 feet from where we have the flash to the wall, but I did that calculation when I thought we were shooting at ISO 100.
So what we need to do is dial that flash down from full power to quarter. Lauren: I see, okay. Brent: And we're going to use a green gel, because I don't really like the pink. The way that I've set this scene up is that I'm lighting each one of these elements independently. So the background in this case is just like the subject. So I'm doing my guide number math as if I were lighting the subject, because the background is being illuminated just by this one flash. As long as my lights don't cross one another, I can do that, and I should do that.
So I treat the background just like a subject when I do my flash to subject calculations. All right, that's pretty cool. We've nailed that background exposure. So we got this really long shadows raking across the back wall. It's green. It's urban. Now the next thing we're going to do in that room is turn this other flash on. We've placed it high against the ceiling, and I want to throw a light through this window onto the ground in front of her feet, and we're pretty close to matching the color on the wall.
So we need to dial this one down to a quarter power as well. So what that light is going to do is rake some green light coming through that grating across her feet. It will give a little bit more dimension in the right-hand window, adding a spotted color to that as well. So it's working well with the yellow graffiti. All right, so we've hit the floor with that light.
Let's dial it up to half power. It's coming through nicely. I'd like to bring it up just a little bit. Yeah, that's nice. We're good. Okay, So let me just show you, Savannah, what we got going on here. That's the scene. Savannah: Cool.
Brent: So we'll up pull in a little bit tighter when we end up shooting, but that's where we're starting. Then the last thing we're going to do is put a light on it from overhead to make it look like you're under a street light lamp outside. Okay? So we're there just testing that one. Lauren: Want me to get that? Brent: Yep. So again, that one's got to come down to quarter power. Lauren: Quarter power. Okay, Brent, quarter power with orange gel on it.
Brent: Yep. So what we're trying to get from the overhead light is the feeling of a sodium vapor light, and it's going to cast a little bit of light at her feet and give maybe a tiny bit of hair light too. What's the zoom head setting on that? Lauren: Zoom is 80. Brent: Okay, let's go to a 105 and then knock the power back to 1/8th power. We initially had the overhead light that was going to emulate the street lamp set at a zoom head of 80 millimeters, and that cast a beam that was barely noticeable on the test shot, but it cast a beam that was a little bit broader than what I wanted.
So what I asked him to do was to increase the zoom head setting to 105 millimeters to narrow that down and after he did that I asked him to reduce the power setting by one stop to compensate for that more concentrated beam of light. I really didn't get the full effect of that overhead light that I was hoping for and the reason for that was that I've created a normal exposure on the model and on the wall. So the additive effect of that overhead light is pretty small.
What I could do would be to go in in post- production and kind of modify that and fix it, but it really didn't work quite the way that I'd hoped for. Had I put a snoot on that key light on the left-hand side and funnel that light directly onto her and minimize the spill onto the background wall, then I would have seen what I was looking for. But this setup just didn't quite work the way that I anticipated. So, Savannah, we're going to do maybe a dozen takes on this just hit that mark, you'll see the flash go off, go another stride. Then we'll just start over.
So you can look in a different direction each time. Occasionally, give me a little bit of volume with your skirt and just do what you're good at. Then we'll just go slow, because I want to make sure that all the flashes recycle each time. So there's no rush. All right, good. Keep coming. Great.
So, even though I didn't get the full effect of that overhead light, there is a little bit of a rim light and a hair light showing up on the model. So it did give me a little bit of added value for having that light up there. This time, Lauren, let's make a small change. When she's got that skirt coming out, I'd like to be able to blow that light through it as well, because it's disappearing, so maybe we can cheat it over so that we still get some spill coming through this window, but also here.
Lauren: Here, before she goes through? Brent: Yeah. Lauren: Okay. Brent: All right, fire it up. Good deal. Lauren, let's turn that smoke on and see what happens here. So let's really fill that room up, and then we'll see what-- Lauren: Fill it up? Brent: Yeah. I'll shoot as we go. All right, that's good, Lauren.
Okay, do that again as soon as that flash recycles. So let's give it 10 seconds. So this is another reason to shoot at a higher ISO, because it allows us to use a lower power ratio, which will save batteries. So we'll swap those out when we're done. So I really liked what you did. Yeah, that's nice. We're good. Savannah, this time we're going to do a tighter kind of head and shoulder shot and then maybe a little bit looser, but we're going to narrow down on the background for sure.
The way we're going to illustrate this is by turning one light on at a time. So I've got same green gel on a C-stand over your left shoulder, and that's going to produce a little bit of a rim light. So I'm going to take that shot now. So you can just hang out. There is this very subtle light on her left side. Then, Lauren, if you could turn that hair light on. Lauren: Okay. Brent: Thank you. So, now we've got a nice little hair light with a bit of spill on her shoulder.
I'm going to run in and turn the background light on. I've changed the gel to a blue gel, a very deep, dark blue gel. I want to get a, oh, 2 & 1/4 or 2 & 1/3stop under-exposed backdrop, and we should just get a nice blue rich backdrop going here. That fired. I'm going to turn on the key light. Nice.
Okay, we're in business. So I'm going to move in. I am going to shoot vertically. We've got all the lights. We nailed the key light exposure. We did the guide number math. Guide number 90 divided by 6 feet gave up f/16. I didn't want to shoot at f/16. I want to shoot pretty wide open at 4. So, what we did is we dialed that key light back to 1/16th power, and that allowed me to open up to f/4.
Beautiful. That's great. I'm shooting too fast. So what I want to do now is increase the ISO by three stops, that's going to allow us to dial the strobes down by three stops as well. In the case of the key light we're going to go from 1/16th power to 1/28th. In the meantime, I'm going to increase the ISO from 100 to 800, and then we'll have to make the changes on our background lights as well.
What this is going to allow me to do is just shoot really a lot faster, which is going allow Savannah to be a little more energetic and playful without breaking rhythm. So we'll get that. Now we're just going to shoot pretty quick. So I'm going to move around a little bit. I going to get it off the tripod, and we'll just have some fun. So I increased the ISO to allow me to shoot faster.
By increasing the ISO, I could dial the power down on the strobes, which saves batteries which saves recycle time which allows me to shoot at a much faster pace. Nice. All the flashes are firing right on time. Let's shake this up a little bit and soften that key light now Lauren. While we're shooting these if you could just look and move across the clock. So if you can look a little bit towards the light and then come back to me.
Start at the light. Okay, eyes at me. Great. We got beautiful exposures. The shadows are a little tough because it's on modified light. It's going to work for some of these shots. But, Lauren, let's bring in that diffusion reflector. So what we're going to do is just fill in the shadows very passively without using another light and without changing the exposure on the key side of the face.
Let's get it right in tight. Lauren: Okay. Brent: Okay, great. Nice. Now, if you can go back that way with your head. We got those fluorescent lights in the background which is really cool. We are keying off of the fluorescent tube. Lauren, let's put an umbrella on that guy.
So by shooting at f/4 at such a high ISO, I'm getting a little bit of light from the bulbs on the inside which is illuminating one of the building posts which really looks good. That green against the blue. So it's a nice little mix of ambient and strobe. Now, let's see here. Great.
Let's bring that light around, and now that we've diffused it, let's drop it just a little bit. Okay, and the thing that I failed to tell you to do was to compensate for the umbrella. So let's bring it in a stop and a third. So we're going to go from 6 feet to 5.6 to 5 to 4.5 to 4 feet. Lauren: 4 feet.
Brent: Yeah. I should have checked. Nice. All right, those exposures are much, much better. So let's use this to our advantage, and if you want to step behind that, I will just swing this around a little bit. Let's see what we get with that. Now step in between them.
Let's kill the overhead light, and then we'll take a few more, and then we'll be done. Lauren: All right, The reason that I killed the overhead light was that when I asked her to step back into that, it was beginning to spill a little bit too much onto her forehead and nose. So I wanted to get rid of that and really just get a soft light on her. That's beautiful. Thank you. All right, that's a wrap.
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