Photostability measurements are required in the pharmaceutical industry to characterize the effects of light on the degradation and efficacy of their products. Measurements in the UVA and visible spectra are made in chambers that accelerate the testing. As two types of lamps are used, and the effects of both spectral regions must be independently measured, most systems include 2 detectors: one for the UV and one for the visible.

International Light has two systems preconfigured for this application, the IL1720 and the IL1420, both of which include the radiometers and detectors configured for both spectral measurements. Detector assemblies for this application can be purchased separately. They are the SED(SEL)033/UVA/W for the UV measurement and the SED(SEL)033/Y/W for the visible measurement. Measurements are made in the accepted radiometric units of W/m² in the UV and lux in the visible. An integration mode allows energy measurements in J/m² and lux*s.