# Measurement of Circadian Effectiveness in Lighting for Office Applications
## 4 Discussion  
In this work, a novel methodological framework for the performance of in-field light measurements has been proposed and validated that allows for a spatially resolved approximation of the circadian effectiveness of a lighting situation in terms of the physiologically relevant CS measure using an imaging photometer. As it has been shown, this framework can easily be adapted to comply with arbitrary FOV definitions and, at a later stage, extended accordingly to enable the directional weighting of lighting contributions emerging from different parts of the lit environment. The latter, in particular, constitutes an open field of ongoing research with still a lot of unknowns so that, at present, no specific recommendations on how to weight light contributions from different directions to come up with a reliable estimate of the circadian effectiveness of a lighting condition do exist or can be made yet. Nonetheless, the current work clearly shows the flexibility and accuracy of the proposed approach in evaluating spatially resolved in-field light measurements with regard to the determination of an overall circadian effectiveness of the prevalent lighting conditions by reporting results for different exemplary FOV definitions in the office context. In particular, it could be shown that the resulting vertical illuminance-at-eye and CS measures not only strongly depend on the specifically applied FOV masking but also on the angle of measurement, although the horizontal illuminance and with it the luminance distribution on the office desk do not change. Assuming a standard layout of the lighting design for office environments, i.e., light is primarily coming from above the observers/from the ceiling, a declination of the measurement angle towards the computer monitor's position on the office desk yields a significant reduction of the respective outcome measures, which complies with the reduced amount of (ceiling) light supposed to arrive at the observers' eyes when their gaze is fixated to the computer monitor. For a reliable estimate of the true circadian effectiveness that can be expected in the field, it is therefore not only crucial to know how light contributions from different directions must be weighted but also to know where exactly and for how long an office worker is gazing. Of course, this kind of information seems to be unrealistic to be obtained on an individual level; however, the goal should be to develop representative statistical probability models of gaze behavior that, in addition to the future introduction of a weighting scheme for directional light contributions, can be used to obtain a true and reliable prediction of the circadian effectiveness of the lit environment from corresponding in-field measurements. As for example described by [PERSON] (101) for the automotive context, the required data to develop this kind of statistical models can be obtained by combining in situ eye-tracking [102] with state-of-the-art object recognition algorithms in order to determine characteristic gaze behavior distributions of office workers for a typical office day, e.g., like in the present case, with a focus on display work. The availability of such context-dependent eye-tracking based gaze behavior models does not only help to perform more