## 1 Introduction  
Modern indoor LED-based lighting solutions make use of several different LEDs with different spectral emission characteristics to allow for a dynamic adjustment of correlated color temperature, color rendition and other more physiologically relevant parameters [1]. Depending on their purpose of application, multi-channel LED systems can for example be tailored to achieve more preferred light conditions, improve perceived naturalness, or increase the users' state of health and well-being [2, 3, 4, 5]. In contrast to many traditional light sources, such as incandescent or compact fluorescent light bulbs, LEDs are driven by direct current (DC) and, therefore, require suitable dimming strategies. Commonly used LED driver control methods that have successfully been applied in the smart-lighting context include analog 0-10 V dimming [6, 7, 8] as well as digital protocols such as DALI [9, 10, 11] or ZigBee [12, 13, 14] standards. In the former case, a DC voltage between 0 and 10 V is used as a simple control signal to be sent to the actual LED driver [6], which eventually adjusts the LED load current and, thus, the light output in the range from minimum (typically between 1 and 10% depending on the driver design) to 100%. The corresponding electrical specifications are defined by the IEC standard 60929, Annex E [15] for both DC voltage and pulse-width-modulated (PWM) LED control. Instead of using analog control signals, the various digital protocols on the other hand make use of encoded data packets to be distributed within the lighting device network to send dedicated commands to the individual LED drivers. The DALI standard, for example, which is regulated by the IEC standard 62386 [16], enables digital information to be transferred between the DALI controller and all network devices by means of an asynchronous, half-duplex, serial protocol over a two-wire differential bus at a fixed rate of 1200 bit s\({}^{-1}\)[11]: The DALI controller, serving as the master device, sends 16-bit Manchester-encoded commands to any addressable slave device on the network (forward direction), which, in turn, may respond with 8-bit Manchester-encoded messages (backward direction) that include, e.g., information on the status of the corresponding luminaire and LED drivers. Despite these fundamental differences between analog and digital dimming strategies, it should be emphasized that, regardless of the chosen method of control, the system's complexity as well as the number of theoretically composable light spectra increase disproportionately fast as the number of LED channels that are built into modern luminaires increases [17]. In current lighting research, light spectra are usually selected based on some pre-defined lighting parameters for which the luminaires' emission will be optimized [18; 19; 20; 21]. However, it should be noted that spectra with an equal chromatic appearance can exhibit quite different spectral compositions, which is known as metamersim [17; 22; 23]. This commonly leads to a bias in the optimization-based selection of spectra for lighting research as one can never be sure that a particular selection is most representative in terms of generalizability. The use of a different selection of metameric spectra might alter the study results and, as a consequence, enforce potentially distinct study conclusions. To profoundly explore the more fundamental relationships and interactions between lighting conditions and other, in particular, dynamic output variables, such as for example lighting preference as a function of the observer's current psychological or emotional state, it is necessary to have an unbiased selection of light spectra that are as diverse to each other as possible. Here, diversity means that the differences in the features representing the spectra must be maximized so that the span of the corresponding spectral space is maximized, too [24]. This optimized space can thus be explored for certain hypothesized relationships and parameter correlations in a completely unbiased way.