# Measurement of Circadian Effectiveness in Lighting for Office Applications
## 3 Results  
This section summarizes the results of the exemplary in-field office light measurements performed at the Laboratory of Lighting Technology, TU Darmstadt, where the proposed methodology discussed in the previous sections was applied. In order to evaluate the accuracy of this novel approach, Table 1 shows the circadian stimulus CS\({}_{\text{IMK}}^{\theta}\) and  
Figure 5: Masking possibilities for the CS\({}_{\text{IMK}}\) calculation considered in this work. (**A**) Half-space geometry; (**B**) field of view definition of CIE S 026:2018 [15]; (**C**) field of view of an assumed 120\({}^{\circ}\) observer. illuminance \(E_{\text{LMK}}^{\Theta}\) half-space estimates as calculated from the spatially resolved output of the LMK-5 color imaging photometer for each of the nine different office workplaces considered in this study and compares them to the CSS-45 measurement results serving as the corresponding reference values. Additionally tabulated are the error estimates \(\Delta\)CS and \(\Delta E_{\text{rel}}\), which were calculated from Equations (11) and (12), respectively. As can be seen, the deviations between the reported LMK-5 color and CSS-45 measurement results are negligibly small from a practical point of view (\(\widehat{\simeq}\)no statistically significant differences between mean values). In all cases, the relative illuminance error \(\Delta E_{\text{rel}}\) is less than 4.3% (\(\varnothing\) = 1.61%), while a maximal absolute deviation of only 0.016 (\(\varnothing\) = 0.011) is observed for the CS values. In summary, these results suggest a relative estimation error of the spatially resolved measurement approach of 3-6%, which denotes an acceptable range for most practical applications. In the present case, the largest \(\Delta E_{\text{rel}}\) and \(\Delta\)CS errors are observed for the workplaces #3 and #9. In comparison to the other measurements, these results can be explained by the greater amount of chromatic information constituting the FOV at these specific workplaces, which can be attributed to the greater number of personalized colored items (textbooks, coffee pots, photographs, etc.) that were present in these cases and the more colorful image content displayed on the respective monitors. As the approximation formula of Equation (5) was developed for white light sources/emitters only, any chromatic content predominating the FOV above a certain degree may result in larger estimation errors. Likewise, the luminance error in Equation (6), from which \(E_{\text{LMK}}^{\Theta}\) is calculated, increases for chromatic content leading to a larger \(\Delta E_{\text{rel}}\) error in cases where the amount of colored, non-achromatic information is predominant in the respective FOV. In order to illustrate how different FOV definitions may alter the measurement results, Table 2 summarizes the vertical illuminance and CS values for each of the nine office workplaces as obtained by applying the different exemplary data maskings introduced in Section 2.3. As can be seen, the average half-space estimates were significantly larger than the corresponding mean values observed for both alternative evaluation schemes. Compared to the results determined for the entire half-space, average reductions in vertical illuminance of 43% and 39% can be observed for the CIE and the 120 deg masking, respectively. A similar behavior must be reported for the mean CS results, where the 120 deg masking gives a 26% smaller value than the half-space evaluation, while an even larger decrease of 29% is obtained for the CIE masking scheme. Even though the latter, due to its elliptical shape, covers a larger area than, for example, the 120 deg observer, it still yields the smallest overall mean values. This finding can be explained by the fact that the corresponding ellipsis only extends up to 50 deg in the upward direction so that, compared to the other two evaluation