## 2 Materials and Methods
### Case Studies  
The multichannel LED system was installed in the Museum of the Cathedral of Seville and the Evangelist Chapel. Both sites were recently restored, ensuring that the artworks were in an acceptable state of preservation throughout the study process. The selection of these case studies is based on the divergent lighting conditions of both scenarios. In the museum, the lighting is significantly influenced by the adjacent courtyard, Patio del Limonar. Therefore, the spectral distribution and resulting CCT of the electric lighting must account for daylight influence. To address this, the SPD of the multichannel system  
Figure 4: **(A)** SPD of the multichannel luminaire, protective glass transmittance and relative spectral sensitivity functions for different exposures materials. (**B**) Critical exposure duration for multichannel and standard LED luminaires, measured in hours. Figure 3: Spectral Power Distributions of the selected light sources, indicating the emulated light with the multichannel luminaire and the real spectrum. is adapted to the daylight spectrum, imitating the color temperature of the natural light source to avoid distorting the hues of the ambient light. Conversely, the Evangelist Chapel lacks natural light influence, so the design focuses on suitable illumination of the paintings and proper color rendering of the altar piece, ensuring both hue discrimination and an adequate balance of chromaticity. An initial setup was conducted in the Museum to determine the optimal placement of the spotlights, avoiding specular reflections on the varnish of the paintings from the observer's position, as shown in Figure 5B. The goal was to cover the entire surface of the painting, optimizing horizontal illuminance uniformity. After the spotlight installation, the SPDs of the multichannel luminaires adapt their CCT according to daylight conditions, as shown in Figure 6. The natural light spectrum from the courtyard is inferred from an outdoor webcam that translates the sky color to a specific CCT, which is then interpreted by the light driver to assign a corresponding SPD to the electric luminaires. The installation of the luminaires in the Evangelist Chapel involved placing spotlights on two rail systems located in front of the altar piece, as shown in Figure 5A. Next, the spectral configuration of the luminaires was adjusted, as can be inferred from Figure 5C, to find the suitable SPD for achieving optimized color fidelity and hue discrimination. The final results, showcasing different CCT configurations, can be seen in Figure 7.  
Figure 5: From left to right and from top to bottom: (**A**) Installation of the multichannel spotlights in front of the Evangelist Chapel. (**B**) Initial set-up of the lighting system in the Cathedral Museum. (**C**) Spectral configuration of the multichannel system in the Evangelist Chapel. Figure 6: Adaptation of the multichannel lighting system in the case study of a painting in the Cathedral Museum, from left to right and from top to bottom: multichannel lamp, incandescent lamp, warm LED, cool LED, CIE D50, and CIE D65. Figure 7: Adaptation of the multichannel lighting system in the case study of the Evangelist Chapel, from left to right and from top to bottom: multichannel lamp, incandescent lamp, warm LED, cool LED, CIE D50, and CIE D65 (image taken from a global point of view, not from the observer’s position). The objective trials--which correspond to the Farnsworth-Munsell and Natural Color System tests--were conducted in the Light Lab at the School of Architecture, University of Seville, shown in Figure 8. This lab is equipped with nine multichannel LED luminaires, the same model used in the case studies of the Cathedral of Seville, allowing the same SPD to be reproduced in a laboratory environment. The luminaires are mounted on the ceiling with an opal diffuser that creates a Lambertian distribution of light.