By Heinz Richter
Most photographers have the misconception that outdoor portraiture allows no control over background brightness. After all, the sun, the only light source, illuminates the subject and the background with the same intensity. However, some simple methods do offer considerable changes in background brightness.
In bright sunlight, subject and background will be exposed the same if both the subject and the background are both lit by direct light. Obviously, this cannot be changed for the background. We do, however, have considerable control over the illumination of the model’s face. Positioning the model such that it is backlit will put the face in a relatively deep shade. Correcting the exposure for the face requires more exposure. This of course also means more exposure for the background, with the result that the background will be substantially lighter. This is referred to as key shifting. The relatively flat lighting on the face of the model might be less than ideal and side lighting might be a lot more desirable. Repositioning the model to allow side lighting from the sun will bring the exposure of the background back to normal since again both, the light side of the face and the background are lit with the same intensity. However, positioning the model next to a tree will lower the light intensity substantially. In addition, the side of the face facing the tree will be shaded from the ambient light under the tree, allowing the other side of the face to be lighter. This will effectively create soft side lighting. Again, the light intensity on the model’s face is substantially lower than with direct sunlight. The resulting exposure correction will again overexpose the background, resulting in a substantially lighter background.
What if no trees are available?
Any location shoot can only be successful with careful planning ahead. The choice of location will of course predetermine if natural gobos like trees etc. are available. If not, some simple accessories can create the same effects. A piece of black foam core makes a great substitute for the tree. The illumination of the face in these cases is totally dependent on the intensity of the ambient light. Much greater control, and subsequently control over background brightness in the photograph can be exercised with the help of scrims or diffusers. Positioning the model such that the face is crosslit by the sun, and then placing a scrim between the model and the sun will do the following: First of all, the light will be a lot softer, since the harsh sunlight is now diffused. In addition, the scrim will absorb a certain amount of the light, again making it necessary to expose more, which again will render the background lighter. A second or third scrim will of course lower the exposure values on the model even more, making the background even lighter. Yet, the lighting ratio between the lit and the unlit side of the face is again dependent on the ambient light level. Control can be exercised here by blocking the ambient light on the shaded side of the face with gobos at varying distances, subsequently allowing a large amount of control over the final lighting ratio.
How bright the background will be in the photograph will be very much dependent on what we choose for a background in the first place. Needless to say, if a very light background is desired, anything dark like pine trees would be a bad choice to begin with. A relatively light background, like sunlit grassy areas can be rendered quite light with the above method. Sand on a beach, on the other hand, can be rendered virtually white by applying the above controls.
The next question is how to make the background darker. Is that at all possible? Of course it is, within reason.
Here again, the initial choice of background will make a huge difference. But, besides that, there are additional means to effectively render the background darker. Again, the basic light source is sunlight. In order to render the background darker, it is necessary to increase the light level for the model. The resulting exposure changes will then underexpose the background by a certain amount, making it darker. As long as the model’s face is lit by direct sunlight, the initial exposure values for the face and the background are the same. However, reflectors like silver reflectors, positioned to add light to the model, will also increase the exposure value for the model. This also allows a certain amount of control over the lighting ratios. The face, lit evenly with sunlight, will be lighter on one side if that is where the light from a reflector is aimed. Another method would be to have side lighting from the sun and then using reflectors to add front lighting to the face. Not only will this lighten the shadows, making them less harsh, but it will also add light to the sunlit side of the face. This too will increase the exposure value of the face. Again, the resulting exposure correction will underexpose the background, making it darker. How much darker will ultimately depend on the efficiency of the reflector material. Using diffusing reflector material is generally desirable, because it will not cause any distinct shadows like a highly reflective material like a mirror would. This allows more than one such reflector to be used, which would increase the light level for the model even more, resulting in an even darker background. Multiple reflectors will also allow considerable control over the final lighting ratio, since they can be used to add various amounts of light to both the light and darker side of the face. In addition, a reflector can also be used to add a hair light to the set, if such should be necessary.
The above examples are meant to explain the basic approaches available to a photographer to control background brightness with outdoor shoots. I am sure that there are many more examples of how this can be done and how the use of scrims and gobos can offer e great measure of lighting control with outdoor shoots. Photography is, without a doubt, an ongoing learning experience and often there is more than one solution to a problem.