While photoredox catalysis continues to transform modern synthetic chemistry, detailed mechanistic studies involving direct observation of reaction intermediates and rate constants are rare. Using a combination of steady state photochemical measurements, transient laser spectroscopy, and electrochemical methods we rigorously characterize an α-aminoarylation mechanism that is the inspiration for a large number of photoredox reactions. Despite high product yields, the external quantum yield of the reaction remains low (15-30%). Using transient absorption spectroscopy, productive and unproductive reaction pathways were identified and rate constants assigned to develop a comprehensive mechanistic picture of the reaction. The role of the cyanoarene, 1,4-dicyanobenzne, was found to be unexpectedly complex, functioning both as initial proton acceptor in the reaction and as neutral stabilizer for a 1,4-dicyanobenzene radical anion. Finally, we utilize kinetic modeling to analyze the reaction at an unprecedented level of understanding. This modeling demonstrates that the reaction is limited not by the kinetics of the individual steps but instead by scattering losses and parasitic absorption by a photochemically inactive donor-acceptor complex.