Back to black

When you see a macro photo of an insect that is well-lit, but the background is pure black, how has it been achieved? Tim Bold

AThere are several ways in which you can achieve this look, Tim. The most obvious is the use of flash: the flashgun lights the close subject, but the background is further away so the flash power isn’t great enough for the time the shutter is open to reach and illuminate it. Therefore, you end up with black backdrop. There’s actually a ‘law’ for it, called the inverse square law.

Basically, when you double the distance the light needs to travel, the light intensity is reduced to a quarter of its power.

If you were to triple the distance, the intensity would be one ninth of the original brightness. The further the background is from the point the flash is positioned, the darker the background becomes; and if it’s far enough away, it will be pure black.

It’s also possible to create a black or very dark background with either natural light or LED lighting, as long as the subject is lit and the background is in shadow. In this case, by exposing for the illuminated insect, the darker background underexposes sufficiently to look black or near-black. It’s often the case that even a dark-looking backdrop has a range of light levels, so you may find that some areas are black, and some areas underexposed but still visible.

For the shot below of a newly emerged dragonfly, waiting for its wings to work,

I lit the dragonfly with an LED light, so the exposure was 1/400 sec at f/8. The power of the LED was not enough to reach the dark area of bush behind the pond, so the background is underexposed to the point it is black. That said, if you look at the edited image where I’ve pulled some detail out of the shadow in the raw file, you can see some of the greens in the foliage and a stem in the bottom-left of the frame. This shows that the background wasn’t perfectly black: it just wasn’t illuminated enough to show the detail within the camera’s dynamic range.

Black backgrounds are a good way to show the beautiful detail in an insect without the distractions of a background, but sometimes the colours in a natural backdrop can help to give the shot context, so it’s not something you always want to do. You can easily manage your light source so that a black background is generated.