Macro photography generally involves subjects at very close distances - distances that yield a very small DOF (Depth of Field). To counter this small DOF, very small aperture openings (around f/16) are typically needed.
To get enough light onto the DSLR sensor at this aperture, a slow shutter speed (and a tripod) and/or a flash are usually required. If the subject is moving at all, the flash scenario is required.
At these short distances, a shoe-mounted flash will often go over the top of the subject or be blocked by the lens and lens hood.
A Sto-Fen Omni-Bounce Diffuser can be used to redirect some of the light downward, but the result is a rather harsh light because the size of the light source relative to the distance of the subject is quite small. Moving the same light source closer to the subject results in a softer (generally more desirable) light.
The solution is to use a highly adjustable Macro Flash Bracket.
After doing some extensive searching for the right field-portable lighting to use with the Canon EF 100mm f/2.8 USM Macro Lens and Canon EF 180mm f/2.0 L USM Macro Lens, I chose the Wimberley Macro Flash Bracket (AKA Wimberley Shape-Shifter Macro Flash Bracket).
The Wimberley Macro Flash Bracket provides excellent lighting control!
This has to be the most flexible macro flash bracket available (or inventable for that matter). Loosening one of the two knobs on the adjustable part of the bracket enables two of the four ball joints to move. Adjust the angles to fit your desire - and fire away!
Need a second macro bracket for two flashes? Get a second ShapeShifter. Multiple brackets can be attached to one lens plate. Enough space is needed on the plate to attach the second bracket - the camera body plate can be used for an additional Wimberley Macro Flash Bracket as well. Wimberley Lens Plates allow attachment to the top and bottom of the plate.
Here are the parts you need for the Wimberley Modular Flash Bracket system attached to a collared lens (in addition to an external flash)...
The ShapeShifter can also be used directly on a camera body for use with a lens without a tripod collar. To use in this way, a Wimberley Flash Bracket Perpendicular Plate and a Camera Body Plate are needed in addition to the above list. The Lens Plate is not required in this scenario.
The construction quality of the Wimberley Macro Flash Bracket is excellent. You will not be disappointed!