# Measurement of Circadian Effectiveness in Lighting for Office Applications
### Light Measurements  
To evaluate the circadian effectiveness of typical workplace lighting conditions, suitable light measurements are required. In this work, a spatially resolving luminance imaging photometer LMK-5 color (TechnoTeam Bildverarbeitung GmbH, Ilmenau, Germany) was used to measure the luminance distribution in the visual field of office workers while doing typical computer work. Besides providing spatially resolved luminance data, the imaging photometer system is also capable of acquiring corresponding color information. A combination of built-in filters intended to approximate the CIE 2\({}^{\circ}\) color matching functions [98] allows for a pixelwise estimation of the \(XYZ\) tristimulus values of the image content, or more precisely of the light-reflecting objects in the visual field. These colorimetric data in conjunction with the vertical illuminance per pixel calculated from the respective luminance matrix can be used to obtain an estimate for the CS values experienced by the office workers based on [PERSON] et al. 's approximation method (see also Section 2.3). As can be seen from Figures 1A,B, the imaging photometer is equipped with a fisheye lens enabling to capture the complete half space to assess the non-image-forming (NIF) effects of the illumination of the workplace (incl. self-luminous displays) and its surroundings. For evaluation purposes, an additional spectral radiometer sensor CSS-45 (Gigahertz Optik GmbH, Turkenfeld, Germany) is mounted next to the imaging photometer on a standard camera tripod and is used to measure the spectral irradiance \(E_{\lambda}\) integrated over the complete half space with a proper cosine correction. These measurements are eventually used to calculate CS according to [PERSON] et al. 's original model formalism and allow for a direct comparison between model predictions and approximation results. In total, nine different office workplaces at the Laboratory of Lighting Technology at the Technical University of Darmstadt, Germany have been selected for this study to serve as generic examples of typical office environments. Corresponding light measurements are performed with regard to the circadian effectiveness of the prevalent lighting conditions including daylight entry through windows. The workplaces are all located on the 2 nd floor of the institute's building shown in Figure 2 and are distributed over four different medium-sized, white-painted office rooms with an approximately \(4.5\,\mathrm{m}\times 5.7\,\mathrm{m}\) layout and a height of \(3.2\,\mathrm{m}\). As illustrated in Figure 3, each room comprises two \(1.45\,\mathrm{m}\times 2\,\mathrm{m}\) window areas for natural daylight entry. In each case, the artificial room illumination is realized by four Quadrature(r) 5 MQ238D2H pendant office luminaires (SITECO GmbH, Traunreut, Germany) suspended from the ceiling at a height of \(2.8\,\mathrm{m}\). Each luminaire offers a direct-indirect light emission characteristic, see Figure 4, provided by two LT T5 54W/958 NARVA BIO vital(r) 5800 K fluorescent tubes (NARVA Lichtquellen GmbH & Co. KG, Brand-Erbisdorf, Germany), one for the up- and the other for the downlight component, which are mounted to a slim linear housing with micro-prismatic optics to ensure a homogeneous, glare-free room illumination. Each workplace is equipped with a laptop that is connected to a 24-inch computer monitor. As can be seen from Figure 1B, the monitor is centrally aligned to the office desk, whereas the laptop is accordingly placed on either its left- or right-hand side depending on the preference of the user. Additional objects available in the visual field, such as textbooks, coffee pots, keyboards, etc., as well as the image content displayed on the computer monitor are also user-dependent and not controlled by the experimenters in order to obtain a more realistic cross-sectional representation of the actual working conditions. Figure 1: Measurement setup.