Backlight: Exposure, Options and Techniques

The sun was striking these still-green leaves on a bough backed by brilliant color and stark trunks. The difference between the bough and background was about 1.5EV, but reading right off the bough made the colors in the background to go darker, which created a strong play of brightness and color.

As the term implies, backlight is a strong light behind your subject as it faces the camera. In some cases it can cause exposure problems, but it is also one of the most beautiful light sources for translucent subjects. Think of stained glass windows in a church. They are rather dark and dull when the sky is overcast, but when the light comes through them they are the most glorious window treatments of all.

Backlight is inherently contrasty, meaning that there will be a considerable difference in exposure between parts of the subject and the light behind it. In some instances this means that parts of your subject will either sit in silhouette (having form but no detail within the form) or be considerably underexposed. The key to backlighting is to exploit this contrast, to use the shadows it “throws” toward the camera as part of the composition. You do this by biasing exposure toward the brighter light. The usual solution to getting detail in a subject that is backlit is to use flash to “fill” the foreground subject with light, but that defeats the purpose and dramatic potential of this kind of lighting.

Tools and techniques: spot metering mode, exposure compensation, autoexposure lock.

The bright light here is supplemented by reflections off the pond, which provides a natural fill light for the darker parts of the scene. Nonetheless a spot meter reading of f/16 at 1/250 second at ISO 200 was made directly off the bright yellow leaves on the left side of the frame.

Perhaps the most colorful season in which to exploit backlighting is fall, when brilliant color displays combine with low angle light. The key to exposing this type of lighting is to avoid bringing shadow areas into consideration and read from the backlit leaves themselves. This is easily done by using spot metering mode and locking exposure on the brilliant light of the leaves. In most cases this will be the proper exposure, but in some instances you might want to use a + exposure compensation to add some brightness to other parts of the scene. This rarely goes above +0.5EV. Once you attain the exposure and review it to make sure it does the job, lock it, or switch to manual mode to maintain the exposure as you work in the area.

If you are shooting in the shade with a bright sky behind the main subject you can either crop out the sky and not worry about contrast, or expose for the main subject and deal with the bright backlight later in processing. These formations sat in deep shade but I wanted the sky for relief of the forms at the top of the frame. I used CWA to make the exposure, locking it on the formation itself, then recomposed. Later in post I selected the sky, which was blank in the recording, and added a very light blue color wash.

There may be times when working with backlight that the sun is higher in the sky and/or cannot be absorbed by a dense background.  It is essential to then make sure you block the sun from both the image and from exposure consideration. I often do this by finding a shadow area cast by the foreground subject and stand within it to make the picture, or at least position myself so that I block the sun with a branch, rock or other obstruction. Failure to do this will result in flare and an exposure that is thrown off by the strong presence of a direct light source. In addition, it is never a good idea to look through the finder directly at the sun. In this shots I used a branch to black the sun and took my spot reading from the leaves of the center tree.