LIGHTING SETUPS WITH TWO LIGHTS
by William Lulow
A while ago I wrote a piece about lighting a portrait with only one light. Here, we begin to discuss how to add a second light to your setup and what kinds of effects it produces.
After you’ve played around with lighting someone with one light, what did you learn? How do your pictures look? What would you like to change, if anything?
For most of us, one light source creates great shadows and highlights in a portrait. The images are mostly dramatic. Perhaps, they are too dramatic for many commercial uses. So, what do you do? The answer is to add a second light. But, the second light needs to be added in a way that doesn’t completely destroy the light that you’ve produced from the first light. This light we now call the “MAIN LIGHT.” The second light you add is called the “FILL LIGHT.”
THE FILL-IN LIGHT:
As the main light gives the initial definition to your subject, the fill-in light is used to add information to your photograph. You may remember that most of the results produced with only one light tend to be very dramatic with harsh shadows and lack of detail. The purpose of adding extra light therefore is to give more detail where a camera doesn’t see it! The concept here is that artificial lighting exists to help the camera see what the eye knows is there. Our eye-brain combination is quite sophisticated. It sometimes “sees” things that are not actually there. For this reason, if we as photographers are going to translate something seen in our “mind’s eye” so to speak, we have to decide exactly how much we need to help the camera, see as we are seeing. The fill-in light will assist us in this endeavor. The fill-in light is normally a light of less intensity than the main light, placed on the opposite side of the camera as the main light and diffused, or softened, as much as desired. One thing to avoid in placing a fill-in light is a double set of shadows on the subject which is created when two light sources of equal intensity are placed on opposite sides of the camera position. This creates an un-natural looking effect. This is so because there is really only one light source
in our universe – the sun. Maybe if there were two suns in our world, double shadows would look normal but…This is the main reason for keeping the fill-in light weaker than the main light. We can decide exactly how much detail we want to show by the use of what is called “Ratio Lighting.” This is simply taking accurate measurements of how much light is falling on the subject from each of the light sources and balancing them according to a formula. Without getting into complicated mathematics, light conforms to what is known as the “inverse square law.” This law states that light intensity will vary inversely as the square of the distance between the light and the subject. What this means practically for photographers is that if you place a light 10 feet from a subject and the subject therefore is receiving X amount of light, by moving the light 5 feet from the subject, you increase the intensity of the light by 4X. Conversely, if you move the light away from the subject to 20 feet, you decrease the intensity of the light falling on the subject to .25X. For every f/stop you open your lens you are increasing the density of the image geometrically. For example: f/4 lets in twice the amount of light as f/5.6, four times the amount of light as f/8, and 16 times the amount of light as f/11. For our practical purposes in the discussion of ratio lighting, the following table can be helpful: Assuming light of equal intensity, the following differences in f/stops will provide the corresponding ratios:
LIGHTING RATIO DESIRED DIFFERENCE IN F/STOPS MUST BE
1:2 Equal (Same f/stop)
1:3 1 Stop
1:4 1.5 Stops
1:5 2 Stops
1:7 2.5 Stops
1:10 3 Stops
This difference can be achieved by either moving the fill-in light or changing its intensity by diffusion or reducing its power. The easiest way to take measurements for ratio lighting intensities is to use an incident light meter and place it at the subject position. Then aim the light-collecting dome at the light source and take a reading. With the fill-in light source turned off, take a light meter reading of the main light. This will give you an accurate f/stop reading of how much light is being given off by the light source. Next, do the same thing with the fill-in light and by reading the above chart, you can determine what your ratio is. Remember that the lighting ratio is always an expression of a comparison of the two lights. Most of the time, for accurate rendition of shadow detail in a portrait, you will want to set your lighting so that the ratio is somewhere near 1:3. A 1:3 ratio means that the main light is twice as strong as the fill-in). Similarly, if the ratio was 1:8 it would mean that the light from the main light was 64 times the intensity of the fill-in light. (INTENSITY OF LIGHT VARIES INVERSELY AS THE SQUARE OF THE DISTANCE BETWEEN LIGHT AND SUBJECT). Obviously, from this you can see that the lower the lighting ratio, the more well-lit the photograph will appear. Conversely, the higher the lighting ratio, the darker, more dramatic the photograph will appear. Once you have decided what kind of lighting ratio you want, follow the formula above to achieve those results. By this time, you should be able to set up a main light and experiment with the type and intensity of fill-in lighting. The next step in building a lighting arrangement is to add the background lighting, accent lighting and hair lighting if necessary.
So, here are the examples of a portrait with one light and with two (the second being a fill-in light):
Notice how the shadows are much lighter and you can see details in the model’s neck now with the addition of the second light. As mentioned above, you can vary the amount of detail you show by varying the intensity of the second light.
