# Measurement of Circadian Effectiveness in Lighting for Office Applications
## 3 Results
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**CSS-45**} & \multicolumn{2}{c}{**LMK 5 Color**} & \\ \cline{2-7}
**Workplace** & \(E_{\text{CSS}}\) in lux & \(\text{CS}_{\text{CSS}}\) & \(E_{\text{LMK}}^{\Theta}\) in lux & \(\text{CS}_{\text{LMK}}^{\Theta}\) & \(\Delta E_{\text{rel}}\) in \% & \(\Delta\)**CS** \\ \hline \#1 & 372.4 & 0.359 & 373.9 & 0.351 & 0.40 & 0.008 \\ \#2 & 414.3 & 0.379 & 418.8 & 0.373 & 1.09 & 0.006 \\ \#3 & 372.7 & 0.342 & 362.8 & 0.326 & 2.66 & 0.016 \\ \#4 & 370.0 & 0.343 & 371.1 & 0.331 & 0.30 & 0.012 \\ \#5 & 387.0 & 0.360 & 380.6 & 0.350 & 1.65 & 0.010 \\ \#6 & 399.4 & 0.370 & 394.9 & 0.358 & 1.13 & 0.012 \\ \#7 & 421.8 & 0.372 & 414.4 & 0.364 & 1.75 & 0.008 \\ \#8 & 389.7 & 0.350 & 384.9 & 0.339 & 1.23 & 0.011 \\ \#9 & 257.3 & 0.247 & 268.3 & 0.232 & 4.28 & 0.015 \\ \hline
**average** & **383.7** & **0.351** & **381.7** & **0.340** & **1.61** & **0.011** \\ SD & 39.9 & 0.032 & 36.5 & 0.034 & 1.23 & 0.003 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Illuminance and CS half-space estimates calculated from the CSS-45 spectroradiometric measurements and the spatially resolved output of the LMK-5 color imaging photometer. Additionally tabulated are the corresponding error estimates \(\Delta E_{\text{rel}}\) and \(\Delta\)CS. schemes, larger parts of the light coming from the upper visual field (i.e., the ceiling) are excluded as non-relevant for calculating the respective outcome measures. Sufficiently high CS values (>0.3) are only observed when integrating over the complete half-space, where an overall mean CS\({}_{\text{LMK}}^{\text{G}}\) of 0.340 is obtained. Significantly smaller values of 0.253 and 0.241 must be reported for the 120\({}^{\circ}\) and CIE maskings, respectively. The considerably lowest circadian effectiveness of all workplaces is observed for workplace #9 showing a CS value of 0.232 for the full half-space evaluation, of 0.136 for the 120\({}^{\circ}\) masking, and of 0.138 calculated from the FOV definition of the CIE. Compared to the workplaces #1-8, which were measured on a cloudy day between 12:00 p.m. and 1:00 p.m., workplace #9 was assessed in the evening, where natural daylight entry through windows was significantly reduced, leading to less circadian-effective overall room light conditions in the latter case than reported for the remaining workplaces. Thus far, the reported measurement results of circadian effectiveness at the various office workplaces were obtained for a tilt angle of the measurement devices of \(\alpha=0^{\circ}\) at a height of 120 cm derived from DIN EN 12464-1. However, with the standard desk orientation of a computer monitor being slightly below the horizontal viewing axis of a seated office worker, see Figure 5, it seems to be expedient to also discuss how a non-zero tilt angle may affect the measurement results. Assuming a typical computer work scenario, it can be expected that the office worker's gaze is primarily attracted by the displayed information in front of them and, as a result of the computer monitor's off-axis position, leads to a different overall circadian stimulation than estimated from a horizontal on-axis measurement. Table 3 therefore summarizes for each of the nine different office workplaces considered in this work the respective measurement results obtained for a non-zero tilt angle of the spatially resolved imaging photometer of \(\alpha=-10^{\circ}\) so that its optical axis is aligned to the center of the computer monitor's display. As can be seen, the reported illuminance and CS values decreased considerably. Compared to the horizontal on-axis results shown in Table 2, the average illuminance (CS) values obtained for the half-space evaluation, the 120\({}^{\circ}\) masking, and the FOV definition of the CIE are reduced by 17% (10%), 20% (13%), and 16% (11%), respectively.