Perhaps the most frequently asked question I get at the photo workshops I run is how to get a black background on a macro image. For most beginner macro photographers, the natural assumption is the images they see with the jet black backgrounds must have been made on a night dive. The truth is, they are usually done in full daylight…and creating a black background is one of the easiest techniques in underwater macro photography.
Here are a couple of examples of images made in broad daylight conditions, meaning the water in the background was clear, bright blue and fully illuminated by overhead sunshine.
The process is quite simple. All you need to remember are two things:
With a high enough shutter speed, 1/200 sec. and a relatively low ISO…think ISO100, you will effectively block out any ambient light in the scene, rendering it black.
Your strobes will only illuminate the parts of the scene that contain something that the light can bounce off of.
So with these two fairly simple rules in mind think about why the background of these images look entirely black.
First, the shutter speed on these two images were 1/200 sec., which is the highest shutter speed my Canon 5D Mark III will synchronize at. For macro work, unless you are creating an image with intentional motion blur, my recommendation is to keep the shutter speed at the max your camera will synchronize at. Both images were also shot at ISO 160, and each was shot at a relatively high f stop of f/16. This combination of a fast shutter speed, small aperture and low ISO has allowed my camera to “block” nearly 100% of the ambient light…the bright overhead sunlight.
Second, and perhaps most important, is that I not only pointed my strobes inward towards the macro port, but I shot these images with nothing immediately behind the subjects. This means that the light I was producing with my strobes were not spilling out behind the subjects, I was controlling that light. The lack of anything behind the subjects also meant that there was nothing for any stray light to bounce off of and return towards my camera lens. Since the background is nothing but open water, even though it is fairly bright open water, it renders black since the strobes are not bouncing off the water…the light simply continues to travel away from the camera.
Give this a try…you can even practice this on land in daylight (just don’t have the bright sun in the background). A blue sky will suffice and you can see for yourself how simple this process actually it.