recently started using flash with an on lens diffuser with my macro photography. i own a metz 24 af-1 for my olympus which should be a piece of rubbish really, dual AA, tiny, plastic that rattles etc. its working great. i can achieve good shots iso 200 180th second f8-11, not a problem at all. my macro is 60mm f2.8 (120mm eq on olympus. i also have a metz 44-1 - should be at least half decent mid range, quad aa and costed a load more for Pentax. well, i tried using that with my sigma 50mm macro (75 eq) and at f8 1/180, im needing iso 1600 and higher to get a good exposure. really poor performance not much better than my old method of a video light hooked to hover at 1:1 distance. I've had to extract depth of field and lower aperture to 5.6 and still often bumping up to 1600. how can i work out what the issue is? both flashess look blindingly bright to the naked eye but severally different results, i have given it over 2 minutes at some points to get some charge back. settings for flash EV set 0.7, doesn't look any different at 0.