Too hard to read, let me try, here is the correct formular:(for n flash of guide number of Gn1, Gn2, ... Gnn repectively):combined GN = square_root (Gn1*Gn1 + Gn2*Gn2 + ... +Gnn*Gnn)---if all the flash has the same GN, then combined GN = square root of N (where N>1), simple to calculate, you need 4 flashes to double the GN
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