The Angular Sensitivity Characteristic of a Photometer – an Ignored Parameter

The angular sensitivity characteristic of a photometer is an important parameter when measuring illumination, but in many other situations it is less important, such as measuring luminance, where the incidence of light is normal. The starting point of the research is the finding that there are many situations in which this parameter is neglected, although it should not be. The angular sensitivity can generate errors when measuring illumination, but also in many other configurations where direct or indirect lighting measurements are involved, also for Light Field Analysis, for tracking the angular position, for automatic adjustment of indoor lighting, or even in the case of Visible-Light Positioning Systems. Some such examples from the literature are analyzed to demonstrate this. The experimental approach is based on a goniometric stand, with the help of which angular sensitivity characteristics of some sensors and photometers used in current practice is determined, also following the possibility of compensating cosine errors. The conclusions represent a clearer picture of how this type of error manifests in lighting engineering measurements.