## 3 Results  
### Color Discrimination Test  
The first trial conducted in the Light Lab corresponds to the Farnsworth-Munsell test, where 30 respondents must arrange the color caps of four hue ranges to quantify the ability of a light source to discriminate similar colors. The scores were determined according to the number of color cap transpositions, as described in Table 1. Accordingly, a score of 100% implies that the arrangement of the caps is perfect, while a score of 66% indicates that there were two single transpositions or one double transposition. In accordance with the scores defined previously, Figure 10 shows the results for the four hue ranges (red to yellow, yellow to green, green to blue, and blue to red), defining the average score for each source, the maximum and minimum values, and the second and third quartiles. Figure 9: Objective tests performed in the Light Lab: (**A**) Farnsworth-Munsell 100 hue test for color discrimination. (**B**) Natural Color System test for color fidelity. As can be deduced from Figure 10, the selected light sources offer acceptable color discrimination in most cases, although some nuances can be observed. The spectral power distributions of natural light--CIE D65 and CIE D50--achieve the best performance in comparison to other sources. Moreover, luminaires emitting warm-colored light--incandescent \begin{table}
\begin{tabular}{c c c} \hline \hline
**Score** & **Single Transposition** & **Double Transposition** \\ \hline
100.0\% & 0 & 0 \\
83.3\% & 1 & 0 \\
66.6\% & 2 & 1 \\
50.0\% & 3 & 1 (+1) 1 \\
33.3\% & 4 & 2 \\
16.6\% & 5 & 2 (+1) 1 \\ \hline \end{tabular} \({}^{\mathrm{I}}\) Adding one single transposition.  
\end{table} 
Table 1: Score according to number of caps transpositions. Figure 10: Quantification of the Farnsworth-Munsell trial, showing minimum, maximum, and average values as well as values below second and above third quartiles. From left to right and top to bottom. (**A**) Upper left: Red to yellow hues. (**B**) Upper right: Yellow to green hues. (**C**) Lower left: Green to blue hues. (**D**) Lower right: Blue to red hues. lamp and LED 2700 K--allow poorer hue discrimination, specifically in the red to yellow and green to blue hues. Finally, the behavior of neutral and cool luminaires--LED 5500 K and Multichannel LED (MC LED)--provides the best color discrimination, especially in the ranges from red to blue. The results can be summarized in the analysis shown in Figure 11. The average score for all hue ranges is synthesized for each light source, defining, as in Figure 10, the average, maximum, and minimum values, as well as the second and third quartiles. As deduced from Figures 10 and 11, the best color discrimination is provided by neutral and cool light sources, such as the natural light spectra--CIE D65 and CIE D50--and the neutral and cool luminaires--LED 5500 K (LED55) and Multichannel LED (MC LED). This is because the corresponding SPDs of these light sources offer a rich spectral distribution throughout the visible range, providing sufficient energy in the short wavelength range, as observed in Figure 3. The unbalanced spectra of warm light sources--incandescent lamp (INC27) and LED 2700 K (LED27)--generate an excess saturation of red hues, producing poorer discrimination in the ranges affected by red, as seen in Figure 10A,D. Analyzing the daylight spectrums, it can be observed that overcast or blue skies--CIE D65--provide better performance in color discrimination than sunny skies--CIE D50--mainly in the range of blue to green hues, as deduced from Figure 10C. This is because the CIE D65 spectrum offers a higher power distribution in the short and medium wavelengths--from blue to green--while maintaining sufficient energy in the long wavelengths--red hues--to properly distinguish the colors. Finally, as observed in Figure 11, neutral and cool luminaires--LED 5500 K and Multichannel LED--provide performance similar to daylight in color discrimination.