The defining characteristic of macro photography is of course that subjects are shot at close distances. As we'll explore throughout this article, DOF control plays a very prominent role in macro photography.
Depth of field is dependent upon three factors: aperture value, focal length and subject distance. Using a longer focal length will result in a smaller DOF. And shooting at a closer subject distance means a smaller DOF.
In macro photography, however, DOF depends primarily on just two factors: aperture value and magnification. At any given aperture value, the higher the magnification ratio, the smaller the DOF. That leaves magnification as the main contributor to shallow DOF. Insect photographers tended to be very strongly polarized between those who insist on taking photos with only available light, and those who use flash on almost all of their photos.
The primary issue in The Great Flash Debate is depth of field. Whichever approach to insect photography you take, you'll find that it's very difficult to get an entire insect sharply focused - either the head is focussed or the wings. Flashers might invest in sophisticated lighting systems, perhaps dual flashes, one mounted on either side of the camera,
each of which reduces the shadows caused by the other flash. However, this also results in an unusual double "catch light" in the eyes of the subject - a single catch light is considered attractive, but multiple or strangely shaped catch lights are a distraction. Another approach to lighting is the macro ring flash, which is a donut-shaped light which fits around the lens and is typically mounted at the front of the lens. Since light comes from all angles around the lens,
sharp shadows are virtually eliminated; however some Available Light people complain that this now makes the subject too flat! The Available Light Crowd also tries to recover the depth of field they lost, usually by using a tripod. Additionally, using a tripod suffers from the same problems caused by sophisticated lighting equipment - lack of mobility, and subject panic leading to subject flight!
An additional issue for Available Light photographers is white balance.
There's no problem if the bug is sunlit, but if it's in shadow then the colors will appear flat. Most insects are small, so you'll need equipment to magnify them. You can use a long lens with close focus of less than 10 feet, fit a diopter lens to the front of a regular lens, fit macro extension tubes between a lens and the camera body, or use a dedicated macro lens.