Balancing Light Bulbs with Strobes

If you’ll balance the room lights with your strobes, it really gives the room a lot of warmth and depth. It gives the room a sense of being lived in, and it makes it look more real. So it’s really important to give life to those practicals by giving them an exposure, so let’s see how we can do that. So when you’re shooting, you have two lights versus your strobes, and your practical lights in a room, like lamps and other Tungsten. Let’s look at the exposure triangle because it’s going to help us understand how to balance these two different light sources when we’re shooting with two lights that are in the same room. Our exposure triangle has three parts: ISO, shutter, and aperture. The ISO controls the scene overall, as we raise it up or down, we’re gonna get more or less exposure. It affects both the light bulbs in the shot and strobes equally. This leaves us two areas on the exposure triangle that allows us to control two different light sources, the shutter speed and the aperture. The shutter speed affects the light bulbs or Tungsten lights and the aperture controls the strobes.

Let’s talk about why that is. In a dark room where there is very little ambient light, the shutter speed does not affect the strobes. It can be long or short, it just has no effect on the strobes. The flash duration of strobes is too fast to be affected by the shutter speed. The only exception to this rule is that faster shutter speeds faster than 180th of a second, they are going to start to clip the flash duration of the strobes and darken the image, but most of the time we’re balancing light bulbs to the practicals of the room with the strobes, we’re going to want longer shutter speed so this is not a problem. So the strobes are not affected by the shutter speed so the aperture is going to control the strobes. If I turn my strobes on, I got a reading of f8 at my subject and with the light meter, I set the cameras after to F8. The light bulbs in the room, at 160th of a second, are gonna be way too dark, so we’re going to need to lengthen that shutter speed. I now lengthen the shutter speed until I get a correct exposure on the practical lights or light bulbs in the room. It’s a very simple equation.

Let’s take a look in an example. My strobe exposure is F14, the shutter is 1/50th of a second. His face has a correct exposure but the light bulbs are a little dark. I want to make them brighter and not affect his face. I’m going to lengthen the exposure to see what it does to the light bulbs. Here we are at 1/25th of a second. Not much time so obviously they are brighter. We’re going to go to 1/30th of a second, obviously the bulbs are getting brighter, he’s away from the bulbs and not staying next to them, so the light bulbs are not affecting his face at all. Here’s 1/6th of the shutter speed and starting to pull out. When we’re using a high aperture like F14, we’re going to need a very long exposure for those light bulbs. But remember, we’re looking at these light bulbs, we’re looking at the filament of the light bulbs, so it’s like looking directly at the flash tube. If this was in a lamp, it would need to be much longer, because we’re not looking at the direct light source, we’re looking at the effect of the light source. I’m going to 1/25th of a second, and for me that looks the best. It’s really a matter of personal opinion, but I like 1/25th of a second. Let’s move on to our shoot.

We did a shot combining light bulbs with strobes and let’s see what we got. We hung 30 light bulbs from cords in a shot. 30 sounds like a lot, but it wasn’t as many as I thought it would be. These are old-fashioned light bulbs; they are fun to work with, you see that really fun-filament inside the bulb? I wanted to have a black and white image, black cords with white lights, black hair with our model, and the white dress had some black accents. She is standing in the middle of the light so the shorter I can make my shutter, the less exposure I’m going to get from the light bulbs on her face. I’m on a Tamron 70-200mm lens, my focal length is about 120mm, it’s slightly long. My aperture is F6.3, because I want a shallow depth of fields, so light bulbs will go out of focus in the background. I started making exposure at 1/4th of a second, and shortened them until I get the best exposure. Here’s my image at 1/50th of a second. The exposure is almost too long, I’m starting to see just a little bit of light on her face but I think I’m okay. We’re gonna move forward at 1/50th of a second. I then added the background strobe, I dialed the power down on those, until they looked good as a light background. I then added a flexible flash upfront with an OctoDome, it has a grid on it. It’s going to come underneath, because I wanted to look like a soft glow of the lights on her face. I then added another FlexFlash as a rim light on her, it’s got a 7 inch reflector with a 40 degree grid in it. Here’s some of the final images from this set-up.

Just to change things up, I then added a blue gel up to the background light and shot some more images. I added a 39 inch reflector, just to add a little bit of feel on her face. Here’s some of the final images from the set-up.

It’s not a hard concept to grasp, but a hard principle to apply. This principle is the same for sunsets, outside lights at night, lamps, any kind of constant light source. Aperture controls the strobe, the shutter controls the secondary or constant light source. So go out and apply this principle, make it work in the images you are shooting, just keep those cameras rolling, keep on clicking.

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