# New Approaches in Dynamic Metrics for Lighting Control Systems: A Critical Review
## 3 Methods
### Assessment and Comparison of Metrics  
The 300 lx and 500 thresholds for DA calculations were chosen to provide a comprehensive evaluation of the indoor lighting environment. The 300 lx threshold represents the widely accepted minimum illuminance level required for comfortable execution of common office and educational tasks [43]. Its inclusion ensures an assessment of basic visual sufficiency and functional compliance. Conversely, the 500 lx threshold signifies a more optimal and desirable illuminance level, particularly suitable for tasks demanding higher visual acuity, prolonged focus, or enhanced productivity [79]. By evaluating DA at that higher threshold, this study can quantify the potential for achieving a superior indoor environmental quality, moving beyond mere compliance to foster improved occupant well-being and reduced reliance on electric lighting. In the case of DAo, DAcon, and DAo.con, the authors considered it appropriate to use the same thresholds applied to DAs of 300 lx and 500 lx to facilitate a comparative analysis between the various illuminance metrics.  
While Useful Daylight Illuminance (UDI) was originally conceived with a lower threshold of 100 lx to quantify illuminance levels below the 300 or 500 lx minimums, common in other daylighting metrics [53; 54], a lower threshold of 300 lx has gained traction over the years [28; 80]. For the present study, it was decided to employ 300 lx as a lower bound for UDI and 2000 lx for the upper one. Since the main objective of this article is to establish a comparison between the different illuminance metrics, the authors considered that a more similar upper threshold for UDI and ASE would facilitate the comparative analysis. Thus, the illuminance values will be divided between the following:  
Figure 2: Average value of sky SPD proposed in both locations.  
Values that fall short of the accepted range: UDI\({}_{\text{<300}}\).
2. Values that fall within the accepted range: UDI\({}_{\text{300-2000}}\).
3. Values that surpass the accepted range: UDI\({}_{\text{>2000}}\).  
For Spatial Daylight Autonomy (sDA), the IES established a threshold of 300 lx, based on the aforementioned criteria. Its complementary metric, Annual Sunlight Exposure (ASE), was concurrently defined with a 1000 lx threshold [52]. Therefore, the thresholds selected for the study at hand are sDA\({}_{\text{300}}\), ASE\({}_{\text{1000-250}}\).  
The calculation of the Circadian Stimulus Autonomy (CSA) in this study followed the methodology established in previous research [61; 62; 81]. This approach integrates the average spectral autonomy from both locations (Figure 2), the orientation of the models, and Equation (7) to derive the final CS values. For London, a consistent threshold of 320 lx was determined for both north and south orientations. In Seville, the thresholds varied by orientation, with 290 lx established for the north-facing facade and 360 lx for the south-facing facade. These illuminance thresholds were derived by setting a target CS value of 0.4 in Equation (7), then calculating the required CL\({}_{\text{A}}\) to achieve that CS value, based on the average SPD of the sky in each location (Figure 2) and considering orientation.  
These thresholds serve as a valuable reference for evaluating circadian entrainment in the specified scenarios, given that, in conventional lighting applications, natural light's SPD variation--attributable to location and climate--exerts only a very limited impact on melatonin suppression throughout the day.