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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.
- Understanding exposure basics
- Reviewing aperture, ISO, and shutter speed
- Adjusting strobe power and flash to subject distance
- Finding the guide number of a strobe
- Making calculations based on ISO
- Understanding power ratios
Skill Level Advanced
So, after we finished our second shoot, we turned right around, and we had this very cool old industrial baler that was sitting there in the warehouse. And so we decided to use this as a prop. And it's relatively small, but it gave us some interesting lighting challenges. The inside of it was a shiny metallic finish, and I wanted to kind of light that to give a magenta glow around the model, and there were some slats in the walls of it that we decided to utilize by blowing smoke into the scene, and backlighting it to create shafts of light coming through this.
So, we had a little piece of equipment that we used I think to great advantage as a background for our model. So let's take a look at what we did. We'll start with the light camera right. Lauren: So, I'll take this around to put green on it, or are you're going to put that front? Brent: Yeah, you can put the green on it, and then we'll just use this other. We decided to utilize a green gel on one of the strobes in the background and a magenta on the other.
The green gel was chosen to kind of play off of the color of the baler itself and then the magenta was a complementary color to that. And the green worked well with the peach dress that the model was wearing. So, I think what we'll want to do, too, again is flag off the light from that strobe from killing what we're trying to do there. Lauren: From back here? Brent: Yeah. Lauren: Okay. Brent: Yep.
Well, that was a mistake. Lauren: So, this is her mark, right at the end of the tape here? Brent: Yep. Brent: I think I'll just lean this against there to try to fill in the bottom too. Lauren: Okay. Brent: Let's start with this reflector, and then we'll see what we get with that.
What's actually happening is it's getting a little bit of light underneath, which is kind of nice too. So, I placed the magenta gel light inside the baler, and I placed it in there so that I could kick reflected light off for the two doors that are open. Then we've got the green-gelled flash behind the baler itself.
And when we blow smoke into that baler, we see the shafts of light coming through those little slats in the wall. And, Savannah, what I want to try to do is use your body to create some interesting shadows on this wall, so we'll have to play with that position. And what that's going to require probably is moving your right foot forward and turning a little bit and giving some gestures with your hand this way. So, what I'd like to do is create something cool there.
So maybe you could extend your right foot just a little bit, more forward towards me. Okay, let's see what happens with that. Let's move that light in. Lauren: The green one? Brent: Yeah. Lauren: Straight in? Brent: Straight in. What I'd like to do would be to emphasize that a little more. Lauren: To tilt it down. Brent: Tilt it down. I was unable to turn the head, so you may have to-- Lauren: Put an apple box under. Brent: Yeah, I want, yeah, to get that.
So, Savannah, here's what's going on. So, this is what I want to try to create, some interesting shadows there. Savannah: Okay. Brent: All right? Lauren: Okay, I moved it in maybe 3 feet. Brent: Okay. Lauren: Tilted it down a little. Brent: Good, and then the last thing is we may have to move those two cutters again. Okay, so as always, we use the guide number math to find our starting point, and then we kind of play it around with the fill light or the magenta light in the back.
Okay, I think we're ready to roll. We'll make some smoke. Lauren: Smoke it up. Brent: Are you seeing her feet now? Yeah, we're going head to toe. So, this time, if you can give me a lot of volume with your body, that would be great, okay. So, I'm going to crank up the ISO to 800.
I'm going to dial this back two stops, and Lauren, maybe you can do the same on all three of those flashes. So, we're going to go down two stops. Lauren: Down two stops, okay. Brent: I made the decision to increase the ISO once again so that I could shoot faster. By increasing the ISO, I'm able to reduce the power ratios which allows me to recycle the flashes faster so that the model can stay more in a rhythm, and we get out the door faster.
So, it's as simple as that. Nice, here we go. Very good. Okay, I'm going to dial this key down a third while you're doing that. Okay, so we're going to do this quick, Savannah. So, you can jump out Lauren. What I'd like to do is put that soft box on this key light.
We'll get in really tight. I just want to see the effect of that, and we'll figure out the guide number math. So here's what we got. This is really pretty trippy. What I want to do is get that light with more smoke on the back of your head, and then we're going to shoot some silhouettes. Then we're going to put the key light back on, but we're going to make it really underexposed, so there's just a little bit of detail and hopefully a lot of mystery. So, if you want to step back in, and I like the way that you've held that out, there you go.
And then, Lauren, you may have to aim it up just a little bit and then turn it a couple of degrees to your clockwise. And I think you're pretty good. So the key is still off, right? Lauren: Key is off. Brent: Okay, and let's make more smoke. So, Savannah, with your right hand, you can hold it out pretty far, and with your left just a little bit. There you go, yeah. Now we're not going to see your face, so this is just nice.
We introduced the fog into the scene to create a little bit of mystery and drama. And the way to really emphasize that or play it up is to backlight it. Now, if you light smoke, fog from the front, you don't get nearly the same effect as if you light it from behind. And you can see the drama in these pictures that's created by that snooted light blowing through the fog. That's really nice. I'm going to turn this guy on. So, the notion is here just to put a little bit of light on her. And I'm not going to bother to do the guide number math, I'm going to take an educated guess.
Lauren: So, more smoke? Brent: So yeah, let's fire up smoke. I think we're ready to go. I'm intentionally showing the hair light, because when it's coming through that smoke, it really adds a nice bit of mystery. Yes, very sweet, those are beautiful. So, that's a wrap with this shot. Okay, so what we're going to do here is try to do something a little bit different. I'm going to get that soft box up close to evenly illuminate her face, and then I want to try to get just a little bit another stop of light into her eyes, and I'm going to shoot this with the Lensbaby.
What I'm doing here is creating something different. I've introduced a second light that I am using to light the model's face. We haven't done that before. We've restricted ourself to the key light only, a single key light. Here, I'm going to do something a little bit different. I'm using a Lensbaby, which has a very narrow point of focus, and what I want to do is focus that lens on her eyes, but I also want to draw our attention to her eyes by using the light. So, I'm going to illuminate her more or less evenly with the light from the soft box, and I have a second light that has a snoot on it, and I'm going to aim that light directly at her eyes.
So, we're going to see a narrow focus reinforced by two things, the focus itself, and the amount of light that's being put onto her eyes. So let's start with--just for grins, let's get this thing at 1/64th and shoot it 400. Lauren: Okay, 1/64th and 1/28th.
Brent: Okay, and I'm going to shoot at f/5.6, and I am going to get uncomfortably close, okay. At this point, I've got that flash in tight, and I know that I've got to really dial the power down in order to pull this off. So, it was just as quick for me now to start out at 1/64th power as it would be to get the tape measure out and do the guide number math. Plus, I've put a soft box onto that flash which kind of blows guide number math anyway.
So, I'm using my experience to get a starting point, and then I'll go off of the histogram if I need to refine it. So, let's dial this down or let's move it back just a tiniest bit. Now, what I really want to do is just get your eyes in. Maybe we'll get some sparkle off of that dress. I'm working now by process of iteration. But you can see my starting point was really close, and we got to the end result in just a couple of moves, and this is where understanding how guide number math works and the fundamentals of light really pays big dividends.
Just by virtue of having that foundational knowledge, if you do need to work by iteration, you can get to the right result much, much quicker. Let's throw the last thing, and then we'll call it a day. Let's see if we can get this magenta spread out a little bit. So, a little bit of diffusion, you can probably even bring one of the panels in or anything that's going to kind of break that up. Lauren: Okay, diffusion frame is in.
Brent: Okay, great. Okay, I'm going to pull back a little bit. The nice thing about working this closely is the background, that white wall in the back has gone completely black, and we're able to shoot fast. So, we've really got a nice effect I think with the soft box illuminating an underexposure and then using that snoot to key in and then that point of focus is accentuated by the Lensbaby.
So, sometimes people who are shooting with big soft boxes will put a hard light right in the middle of the soft box, and right at the subject to give it a little bit of a kick. These are almost elfin-like or wraith-like. Are you happy? Savannah: Mm-hmm. Brent: And we're done, that's a wrap. Savannah: That's a wrap. Brent: Okay, thanks! Lauren: All right, thanks! Brent: Thank you very much! Savannah: Thank you. Brent: Great, I appreciate it!