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Hi, this is Jay P. Morgan. Today on The Slanted Lens we’re going to take a look at strobe power versus aperture and shutter. I get this question from listeners all the time saying, “What aperture should I use? What shutter should I use? I’m going to give you a basic formula to understand the aperture versus the strobe power. 
We’re going to go through some tests so you can see exactly how it relates. And how to figure it out so that you know how to set up the aperture and the shutter when you’re photographing with strobes.
We’re going to start first in a studio situation. This is a complete dark room even though we have lights here to be able to see me for the video. We’ll turn those off when we’re shooting with our strobes. And then we’re going to move into adding a tungsten light in the background. And how does that relate to your aperture and your shutter when you’re using strobes. So let’s take a look at that. Let’s get started. Let’s answer that question: Understanding how strobes relate to aperture and shutter.
All right, so foundational in this conversation, the thing we have to understand the most is that strobes have power settings. This is an FJ400. This is dialed all the way up. It’s giving me all the power. It’s giving me all the 400 watts that this strobe head has. 
Now I can dial it down one stop at a time. I can go down to F or to eight and I just dropped it one stop. I can go down now to seven and I just dropped it one full stop. So does that mean 9 is f/16 and 8 is f/11 and 7 is f/8? No it doesn’t mean that. It means that the power on the pack is going down one full stop.
So when we start at seven and go to 7.5 that goes up a half a stop. If we go from seven to eight that goes up a full stop. So let’s understand that, that the power on the strobe goes up and down by full or partial stops in one tenth increments.
Now let’s figure out how we get the power on this strobe to match to the aperture and shutter on our camera. Before we tackle aperture, let’s start with shutter. Because shutter is the easiest in this studio situation. The shutter almost has no consequence whatsoever. It doesn’t really matter. 
But we can’t set our shutter higher than 1/250th of a second. Except for on some specialty cameras like the Sony A1 which will do 1/400th of a second. But for most cameras now 1/250th of a second is the fastest shutter speed that your camera will sync with the strobes. 
The reason being is, up to 1/250th of a second the shutter is open the entire time and then it closes. 
After 1/250th of a second the shutter starts to open and the bottom curtain follows it and just lets you have a strip or a small strip area that’s going to get an exposure. That means after 1/250th of a second that you’re not going to get an exposure on the entire scene. Quite frankly, most modern cameras, when you have a trigger of some sort on, won’t allow you to shoot beyond their sync speed. So sync speed for shutter, we’re going to set it at 1/250th of a second.
I’m going to shoot every single shutter going down to one second here. And just show you those images side by side, that the shutter makes no difference in this dark room. Remember we’re just going to have the modeling light on for this test. Nothing else. No other lights in the room. All right, let’s go ahead and do that starting off at 1/250th of a second. Let’s take a series of images.
So there’s 1/250th of a second at f/16. If I go back to 1/125th, 1/60th, 1/30th, I’m still not seeing anything. The modeling light is not doing anything. 
I see 1/15th or 1/8th, or 1/4th. I start to see a little bit of a light on her face at a 1/2 a second. 
At one second I’m seeing just a little bit at f/16. Now this F/16 is really, it’s stopped down. It’s using a lot of light and so the ambient light’s not going to show up very fast.
But if we look at this at f/4.5 as an aperture setting, now at f/4.5 we’re going to see how soon we start seeing the modeling light. 
So there’s f/4.5 at 1/250th of a second. We don’t see anything. 
We don’t see it at 1/125th. We don’t see it at 1/60th. 
We start to see a tiny bit at 1/30th, just a little bit. At 1/15th we’re seeing a little more. 
At 1/8th, 1/4th, and then a half and one. 
So at one second the modeling light is now lighting our face. But if we stay back into 1/60th or faster, even at f/4.5 the modeling light is not going to have any effect on our model whatsoever.
So now, how do we know what aperture we’re going to use? There’s two methods. There’s first, is you just guess and shoot, guess and shoot, look, guess, shoot and look, guess, shoot and look. If I’ve got my light here and we get a little bit of experience, I know if it’s that close on full power to her face it’s probably f/16. So I’ll just take a quick shot at f/16. That’s pretty close.
Or you can use a much more reliable method which is a light meter. 
And so when I put my light meter here, I test my light, which I’m blocking there. Put my light meter here. I test my light, it’s f/16. So you can either use a light meter or you can guess and shoot and look. When you get good at this and you use strobes very much it’s not that hard. You know, kind of what that strobe power is going to be. But here’s where the question comes in is, “How do I know what aperture?” And this is why it’s confusing to people. Because I just tested this and people are going to go, “Oh, well it’s f/16 all the time then. I’m going, “No it’s definitely not”. 
If I move this light closer to my subject matter it’s going to get brighter. It’s not going to be f/16 any longer. It’s going to be f/22. If I bring it even closer and I take a reading, f/32. 
If I pan it towards the camera and I take a reading, f/32.6. It got brighter. 
If I pan it way across at the background and I take a reading, you just lit the side of my head, it’s f/16. 
If I take the light and I put it way back here and I take a reading it’s f/11 and a half. So as your lights move in closer to the subject matter they get brighter. As the lights move further away from the subject matter they get darker. It’s a very simple equation. 
The same output of power out of the strobe head will not give you the same aperture. It’s depending on where you put it. So there’s never a constant aperture that you can use. You may know roughly. You know when the light’s about that far it’s about f/16. But it’s going to be within a stop, a stop and a half, two stops on that, depending on a couple of things. And the first we talked about was distance: the closer it gets the brighter, the further away the darker it gets.
The other thing that can change the output of the strobe is what modifier you’re using. So we’ll start off with just a small reflector that comes with that FJ400 and let’s get an f-stop reading on that. And then we’ll start changing it out and see what different things do to the strobe intensity as we modify the light.
So here’s a five inch reflector, it’s f/16.
Let’s take a look at a seven inch reflector, f/16 and a half. It went up a half a stop. That seven inch reflector brought the light together and made it a little more intense. So it’s half a stop.
Let’s try a 10 inch reflector, f/22.9. It went up a stop and a half over the seven inch reflector.
Let’s put a small soft box on, f/11.2. So we’ve dropped. We were high at that large reflector at f/22 and a half. And it dropped a stop and a half when we put the soft box on. Now one more time, let’s get that reading again, yeah, f/11.1, f/11.2, that made a significant difference. 
If I pull the face off of this soft box what does it give us? F/11.9, it went up almost two-thirds of a stop.
So everything changes the intensity of the light. It either brings it up or it brings it down. If we put umbrellas on here, if we shoot through the umbrellas, if we bounce in the umbrellas, everything’s going to change it. If we put an inner baffle in, if I put in the beauty dish insert into this to bounce light back into the box it’s going to bring it down a little bit.
We just talked about how you can match your aperture to the strobe power. Now what that does, it takes away part of the creative process though. You want to choose your aperture based on your creative desire, shallow depth of field or deep depth of the field. Big group of people, deep depth of the field. One person, shallower depth of field. So if you’re going to make a decision based on aperture for creative reasons, you choose your aperture. Now you have to make your strobe match the aperture. 
So say I choose f/5.6. If I take a meter reading and my strobe was saying that I’m at f/11, well then I know I’ve got to dial my strobe down two stops.
Now my strobe is going to match the aperture I’ve chosen. If I can’t get enough power to match the aperture, say I want f/11 and the strobe has a big modifier on it and it won’t give me enough power to give me f/11, I move it in closer. That’s going to up the power and it’s going to get it to the aperture I’ve chosen. So you’re choosing the aperture and you’re making your strobe match the aperture by dialing the power up or down to equal the aperture that you have chosen. So that’s the opposite of the other way where we’re making the aperture, moving the aperture up and down to match our strobe. We’re going to move our strobe power up and down to match our aperture. And we choose the aperture for creative reasons for what we want on set. Depth of field, shallow or deep. That’s the best way to do this.
Okay, so now we’re going to add a tungsten light or a practical light on set. I’m going to turn on a light in the background. How can we get that to register? Now we can use our shutter. We’re going to lengthen our shutter until we see that. 
I’m at f/5.6 and a third. So f/6.3 and I’m just going to just keep lengthening my shutter until I start seeing that in the background. I’m going to kill this work light that’s on me so it’s not lighting the set at all. I’ll leave the modeling light on because I don’t think it’s going to affect us. I think we’ll get a nice burn in with that light in the background. And this modeling light won’t bother us at all. So we’re going to kill those work lights and make it happen. All right, so I’m going to now start. 
I’m at 1/250th of the second. I’m at f/6.3. You see a really faint glow in that practical light at 1/250th of a second. 
So let’s go to half that. Let’s go to 1/125th and take a shot. So there’s that light. It’s starting to glow in there. But not enough. 
We’re going to go to a 1/60th of a second. It’s getting better and getting better. But not near as bright as I want it to be. So we’re going to go from 1/60th, we’re going to go to 1/30th. 
So here’s 1/30th of a second. I’m seeing a little bit of glow in there. That’s nice. But I think I can go a lot further with it. 
I’m going to go over here to 1/15th of a second. It’s getting better. We’re seeing a nicer glow. It’s trying to even fill in that shadow a little bit on the wall back there. 
Let’s go to 1/8th of a second now. That’s looking nicer. It’s not really huge, but I’m getting some glow in that ambient light back there. I’m not seeing any difference in her face yet. So I’m going to keep pushing here. 
I’m going to go now to 1/4th of a second. Look at the difference now. If I look between f/5.4 and I’m starting to see that light in the background is glowing on the wall. There it’s creating, you know, much more light in the background. But is it showing up on her face? I don’t see it showing up too much. You’ll start to see it in the shadows first. It’ll start to open up those shadows. 
For a half a second, that’s almost too bright now. It’s getting pretty bright back there at a half of a second. Yep, I think at about a quarter of a second it looked pretty good back there. It’s a nice combination of the two. At a half of a second it’s still, her face is fine. It hasn’t made it too bright.
So there you have it. That’s how you balance strobe power with the aperture and shutter on your camera. Now if you want to take this outside and be able to shoot outside in natural light, which is really a valuable thing to be able to do using your strobes and natural light, check out these two lessons. 
This one’s fabulous because it’s going to show you the four steps, one, two three, four to quickly set up outside and be able to shoot balancing those strobes with the natural light and not make it look fake. 
This one’s fabulous because it shows you a trick on how to get the same aperture every time from your strobes. That’s something very interesting you should check out. All right, so keep those cameras rollin’ and keep on clickin’!
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