Originally Posted by
Geoff F
Not sure about how your flash set up works, Mat, but when shooting macro subjects with a Speedlite I set the camera manually to suit the scene (shutter, aperture and iso) then allow the flash to find its own level. With a bit of output compensation.
I found that without some negative composition it was usually over exposed and diffusers didn't help because the auto flash output simply increased to compensate for the diffuser.
Diffusers do help with fixed output flash though.