The optimized system was also validated using a model photocatalytic reaction, the reduction of nitrobenzene to aniline using a TiO2 photocatalyst. The obtained reaction rates generally scale linearly with the light intensity and thus match those obtained with actinometry. However, this is different for external irradiation which even under the same incident photon flux and in the same reactor exhibited lower reaction rates at high light intensity. This was attributed to the fact that, contrary to conventional irradiation systems that scale the light intensity by increasing the irradiance on the limited irradiation area, the WLE system exhibits constant irradiance and rather scales by increasing the irradiation area though the number of emitters.