One of the most important aspects of fine art macro photography is capturing a non-distracting background so your subject stands out. I tend to like clean and colorful backgrounds, but there are situations where dark backgrounds may be desirable. This article will showcase one method of how to capture black backgrounds in macro photography. We’ll take a look at using flash falloff.
Inverse Square Law
Flash falloff is a product of the inverse square law, which states that a “specified physical quantity is inversely proportional to the square of the distance from the source of that physical quantity.”
This law explains many phenomena but it’s particularly helpful for photographers in explaining why we get dark or black backgrounds when our subject is set apart from its background.
To explain in simpler terms, each time you double the distance your light travels, the power is reduced by two stops (or 75%). When using flash as your primary light source, the farther your subject is from the nearest background object, the darker the background will appear.
This happens because the flash output is so fast (and the shutter is generally open for a short enough amount of time) that the light from the flash doesn’t have time to reach the background, bounce back, and enter the camera before the shutter closes.
Using Flash Falloff for Black Backgrounds
Take a look at the photo of the damselfly below. You’ll notice that the background is mostly dark with a vertical green ribbon in the center. That vertical green ribbon is some sort of grass or plant that was nearer to the camera than the rest of the background. The light output from the flash was able to reach that plant material and bounce back to the camera by the time the shutter closed. The rest of the background is completely dark because there was nothing close enough for light to bounce off of in the short amount of time that the shutter was open. The damselfly in the foreground is close enough to the camera that the flash output completely illuminates (and freezes) the insect.
The photo of the water lily below is similar to the damselfly in that the flash output was able to reach the lily, but nothing in the background. The lily is nicely illuminated by natural light which really makes it stand apart from the dark background.
Using Flash Falloff to Your Advantage
The photo below of a longlegged fly is one of my favorite photographs. The metallic eyes and abdomen of the fly paired with the mysterious black background make this photo look like a painting. I love the effect that flash falloff produced.
You can achieve this same effect by setting your subjects apart from the background. Keep in mind, however, when it comes to nature photography, some people may feel like this effect is unnatural. Many people have asked if I digitally manipulated the photo to achieve this effect (other than a minimal crop, the photo is original). Others have asked if I took this shot at night.
The reality is, I took this photo in broad daylight in my backyard. The nearest background was actually my ugly yellow garage. Fortunately, the fly was set far enough away from the garage that the flash “fell off” before producing a hideous light yellow background.
About the author: Danae Wolfe is a macro nature photographer residing in Northeast Ohio. Her primary artistic interests include shooting candid insect and botanical portraits. She recently launched Chasing Bugs, a new blog for photographers interested in shooting macro photos of insects in their natural habitats. This article originally appeared here.