Tuesday, December 11, 2007

Lighting for macro

A paper wasp (Vespa sp) taking off from the nest
One of the things that I find annoying about macro work, mine mostly, work that has been done with flash is the bland, black, unlit backgrounds. These give you darn little feel for the environment the animal is in. They happen largely because all macro work is this fine compromise between magnification, depth of field (DOF), available light and flash light.

When you increase magnfication, DOF falls, it's the law. If you want high DOF, which you usually do, that means you've got to nuke the subject with light. When you're adding huge amounts of light using a flash and meter for the flash, it usually is over-powers ambient light. Its so much brighter than ambient light that ambient makes very little contribution to the final image. Hence the black backgrounds. (Strobist on balancing ambient light.)

A hornet leaves the nest to forage
There are off course many ways to deal with this. You can compromise on DOF, use selective focus instead of trying to keep everything in. That allows you to lower your aperture, pour in less light and be closer to the metering you would get from ambient light.

The second is simply to find areas of high ambient light. Not necessarily on your subject but on the background. On some distant object, for instance, which then becomes this nice bright source of buttery background bokeh as in the hornet images in the post. The bright patches in the background come from a tree which the evening light was hitting. It was at least 4 feet away from the nest, completely out of focus and created this lovely warm coloured bokeh. You can also use the sky in this manner, it's almost always a very bright source.

Inbound and outbound traffic

The third is to actually light the background yourself! I personally have gotten so stuck with the idea of lighting my subject that I never think of backgrounds at all. Off course, in my defense most of my earlier images used a single flash which could only be pointed in one direction. So, it was a bit hard to light two things at the same time, now with two I can do more if I want to.

The other good reason for lighting the background, is to be able to separate the subject from the background. When the main subject is lit directionally, it may have parts of it in shadow. This part will be the same near black shade as the background. It's a good idea not to have this so you can tell the shape and form of the subject itself, to separate it so to speak.

Two ways that immediately come to mind to do this, brighten the background as before or rim /back light the subject. The hornet pictures actually have both tricks in them. The back light is provided by a fully zoomed flash, you can even snoot it to prevent spill, the trick is to get the light behind the subject just lighting the edges.

A few more technical details on the hornets in my flickr photostream.

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