Lately I'm shooting macro pics (mostly insects) with Sigma 150 f/2.8 Macro. Decent DOF needs high aperture values and high aperture values need lots of light. If shooting flying bugs very fast exposures are needed too. This combination of small apertures and high shutter speeds asks for enormeous ammount of light, hardly obtainable with natural lighting. Long time ago I've started using powerful flash units at close distance to object in order to get plenty of light. My only remaining item from the film age, Minolta 4000AF flash became a perfect companion to Sigma 150 lens. As this method cancels the need for tripod mount (1/1000 to 1/4000 is more than adequate for handholding), I have turned Sigma's tripod mount collar by 180 degrees in order to get the mounting hole on the top. There I have added a steel right-angle bracket that holds the flash unit modified so the normal hotshoe mount is changed to a 1/4" bushing. Flash unit is connected to a camera by hotshoe adapter and cord. Although this setup uses modified flash unit, I believe that similar setup with slightly different flash mount could be made.