Photons play a pivotal role in modern synthetic chemistry, particularly in the activation of small organic molecules using photocatalysis. Their use has the potential to alter the landscape of chemical processes, ushering in an era of greener and more sustainable methodologies. Of particular interest to the synthesis of pharmaceuticals and agrochemicals is that these reactions often unfold under remarkably benign conditions, such as ambient temperature and visible light. While photocatalysis is well-integrated on a smaller scale, such as in medicinal chemistry, its upscaling often presents significant challenges. Firstly, the sheer volume of photons required for large-scale photocatalytic transformations necessitates several kW of optical power to produce compounds in substantial quantities. Secondly, the attenuation of light as it travels through the reactor diminishes its intensity, leading to undesirable variations in kinetic rates which can, in turn, trigger byproduct formation. Given these complexities, there is an evident demand for precise modeling and straightforward characterization of photochemical reactor technology, providing essential guidance for chemical process engineers.