I bounce a flash with a guide number of 35 (metres... whatever that is in feet! about 115ft if my calculations are right&#33 and it works fine. For 100 asa film it has 3 "computer" ranges of 1-8m @ f4, 0.8-6m @ f5.6 and 0.5-4m @ f8. So, what f-stop are you shooting at?