## 3 Discussion  
Figure 8 shows that, regardless of their nominal CCT, the vast majority (88% for Australia/New Zealand evaluated LEDs and 89% for European Union, United Kingdom, and United States evaluated LEDs) of the tested commercially available LED sources can be classified as P1 (best color rendering quality), P2 (good color rendering quality), or P3 (acceptable color rendering quality) class in the CPC classification. As expected, Figure 8 also shows that CCT is not correlated with the color rendering quality assessed using the  
Figure 11: The CRI R\({}_{0}\) values of the LEDs under consideration according to their CPC classification. The magenta and yellowish dots represent the LEDs, which are applicable in Australia/New Zealand, where CCT is in the range of 3300 K–5300 K. The magenta dots are for the LEDs with a nominal CCT in the range of 4000 K–5000 K, which are applicable in the European Union, United Kingdom, and United States. Figure 12: The \(R_{f,aliin}\) values of the LEDs under consideration, according to their CPC classification. The magenta and yellowish dots represent the LEDs, which are applicable in Australia/New Zealand, where CCT is in the range of 3300 K–5300 K. The magenta dots are for the LEDs with a nominal CCT in the range of 4000 K–5000 K, which are applicable in the European Union, United Kingdom, and United States. CPC method. Figure 7 shows that the CRI Ra values can reach values exceeding 95 for some LEDs in class P1 and other LEDs in class P2. Therefore, this parameter is not sufficient to express the differences between the P1 and P2 classes. The LEDs classified as P3 class have CRI Ra in the range (80-90), and their \(R_{f,skin}\) parameter is mostly within a similar range of values, but their CRI Ra\({}_{9}\) parameter has unacceptable values for proper rendering of the red color (Figure 11). All LEDs classified as out-of-class due to CPC classification have their CRI Ra in the range (80-85) and \(R_{f,skin}\) in the range (85-90), but their COI parameter is out of the acceptable range, exceeding the maximum allowed value by a factor of about 2 (Figure 9). According to Figure 10, LEDs classified as P3 have higher LER (light efficiency of radiation) values than LEDs of the P2 and P1 classes, thereby offering the possibility of reaching the best energy efficiency for luminaires incorporating this type of LEDs. As illustrated in Figure 11, the CRI Ra\({}_{9}\) values (measuring red color rendering) correlate well with the CPC class. The best CRI Ra\({}_{9}\) values (equal to or greater than 90) are obtained with LEDs of the P1 class. Lower CRI Ra\({}_{9}\) values, but still positive, are found for LEDs of class P2 or P3. Figure 9 shows that all LEDs belonging to the P1 class and some LEDs in the P2 class comply with the Australia/New Zealand COI requirements for medical examination room lighting (COI value not exceeding 3.3). The COI parameter is related to the LER value. It has been demonstrated that LEDs with low LER values (230-290) are capable of fulfilling the standard requirements for the COI value (not exceeding the value of 3.3). Furthermore, these LEDs are classified as P1 (Figure 9). The LEDs classified as P2 meet the COI requirements only when their LER is less than 300 Im/W. The LEDs classified as P3, according to CPC classification, have a higher LER (mostly with the value in the range 310-330 Im/W) compared with the LER of P1 and P2 LEDs. Only a few of these meet the COI requirements. The most energy-efficient LEDs with an LER beyond 330 Im/W do not meet the COI requirements. Furthermore, their \(R_{f,skin}\) parameter is less than 90, and the CRI Ra\({}_{9}\) parameter is too low to ensure good rendering of red colors (Figure 11). In Figure 12, the data show that \(R_{f,skin}\) parameter is not a good predictor of the COI parameter. It is interesting to note that many LEDs with a high \(R_{f,skin}\) value (good color rendering of the skin) are unable to comply with the COI requirement of less than 3.3.