We just completed a very successful macro photography workshop where we had access to perfect lighting conditions. We were able to set up in an old barn that was dark on three sides with light coming in from an open door. This sidelight was soft and easily controlled. By being in the barn, we were out of the wind and were able to work more carefully with manual focus and trying different aperture settings to give different effects by varying the depth of field.
One thing we learned about shooting against a dark background was to underexpose the image. We were underexposing by as much as one to one and a half stops to get the correct exposoure. The reason for this is that the camera's light meter wants to lighten the black background to a mid-tone gray, so it overexposes the image. Now if the pictures are not underexposed sufficiently while shooting them, you can make some corrections to the Raw files in the digital darkroom. However, these corrections only go so far.
In the image of the calla lily above, the correct exposure was critically important. White areas in images are easily overexposed, which results in a loss of detail in the light areas. Once this detail is lost, it cannot be recovered in Photoshop. When I am not certain of the correct exposure, then I shoot several images and adjust the exposure compensation while I am shooting - for instance, one at 1/2 stop under, one at 1 stop under, and one at 1 1/2 stops under, etc.
You can also look at the histogram on the back of the camera while shooting or turn on the overexposure warning indicator, which shows white blinking areas on the camera's monitor if areas are too light.
Learning to control and adjust exposure for different types of images in various lighting conditions is a key element to successful photography.
Editor Notes: Doug Steakley teaches two his online photo workshops: Photographing Motion and Basic Masks In Photoshop. Also check out the other excellent online photo courses at BetterPhoto's digital photography school online and photographer certification program.