## 3 Results
### Curve-Fitting with Optimum Screen Luminance under Different Ambient Illuminance Conditions  
3.2.1. Optimum Screen Brightness Curve vs. High Visual Comfort Curve vs. Low Visual Fatigue Curve for Screen Luminance under Different Ambient Illuminance Conditions  
The curve fitting results of screen brightness (second-order polynomial), visual comfort (third-order polynomial) and visual fatigue (third-order polynomial) are shown in Figures 4-6, respectively. Table 6 lists the optimum levels of screen luminance under different ambient illuminance conditions. The functional expressions of these three fitted curves are presented in Table 7. \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & & \multicolumn{6}{c}{**Screen Luminance (cd/m\({}^{2}\))**} \\ \cline{2-9}  & & **3.87** & **21.47** & **42.74** & **64.12** & **84.77** & **106.7** \\ \hline \multirow{5}{*}{Ambient illuminance (lx)} & 0 & 2.79 \(\pm\) 0.15 & 2.88 \(\pm\) 0.17 & 2.97 \(\pm\) 0.15 & 2.79 \(\pm\) 0.16 & 2.58 \(\pm\) 0.16 & 2.45 \(\pm\) 0.14 \\  & 25 & 3.27 \(\pm\) 0.10 & 3.27 \(\pm\) 0.14 & 3.39 \(\pm\) 0.12 & 3.18 \(\pm\) 0.12 & 2.97 \(\pm\) 0.13 & 3.00 \(\pm\) 0.16 \\  & 50 & 2.91 \(\pm\) 0.12 & 3.18 \(\pm\) 0.13 & 3.58 \(\pm\) 0.09 & 3.21 \(\pm\) 0.10 & 3.33 \(\pm\) 0.10 & 3.06 \(\pm\) 0.12 \\  & 75 & 2.73 \(\pm\) 0.17 & 3.00 \(\pm\) 0.14 & 3.00 \(\pm\) 0.14 & 2.64 \(\pm\) 0.15 & 3.03 \(\pm\) 0.15 & 2.82 \(\pm\) 0.17 \\  & 100 & 2.33 \(\pm\) 0.18 & 2.61 \(\pm\) 0.14 & 2.58 \(\pm\) 0.18 & 2.33 \(\pm\) 0.17 & 2.79 \(\pm\) 0.15 & 2.58 \(\pm\) 0.16 \\ \hline \end{tabular}
\end{table} 
Table 4: The descriptive data for illuminance satisfaction (M \(\pm\) SE). \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & & \multicolumn{6}{c}{**Screen Luminance (cd/m\({}^{2}\))**} \\ \cline{2-9}  & & **3.87** & **21.47** & **42.74** & **64.12** & **84.77** & **106.7** \\ \hline \multirow{5}{*}{Ambient illuminance (lx)} & 0 & 2.67 \(\pm\) 0.15 & 3.03 \(\pm\) 0.13 & 2.82 \(\pm\) 0.18 & 2.73 \(\pm\) 0.15 & 2.21 \(\pm\) 0.15 & 2.12 \(\pm\) 0.12 \\  & 25 & 2.91 \(\pm\) 0.13 & 3.18 \(\pm\) 0.13 & 3.55 \(\pm\) 0.09 & 3.03 \(\pm\) 0.11 & 2.82 \(\pm\) 0.13 & 2.88 \(\pm\) 0.14 \\  & 50 & 2.79 \(\pm\) 0.13 & 3.00 \(\pm\) 0.13 & 3 Figure 4: The curve fitting results of screen brightness. Figure 5: The curve fitting results of visual comfort against screen luminance. Figure 6: The curve fitting results of visual fatigue against screen luminance. The optimum screen brightness curve, high visual comfort curve and low visual fatigue curve for screen luminance under different ambient illuminance conditions are shown in Figure 7. The screen luminance levels for optimum screen brightness, high visual comfort and low visual fatigue all increased with increasing ambient illuminance levels. Regardless of the ambient illuminance level, the low visual fatigue curve was always below the two other curves. When the ambient illuminance changed from 0 lx to 100 lx, 20.63-75.15 cd/m\({}^{2}\) was the best range for screen luminance with respect to screen brightness, visual comfort and visual fatigue. 2.2 High Satisfaction Curve vs. Low Visual Fatigue Curve for Ambient Illuminance with Different Screen Luminance Conditions  
The curve fitting results of illuminance satisfaction (second-order polynomial) and visual fatigue (second-order polynomial) are shown in Figures 8 and 9, respectively. Table 8 lists the optimum ambient illuminance under different screen luminance conditions. The functional expressions of these three fitted curves are presented in Table 9. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Standard**} & \multicolumn{5}{c}{**Ambient Illuminance (lx)**} \\ \cline{2-6}  & **0** & **25** & **50** & **75** & **100** \\ \hline Optimum screen brightness & 36.20 & 42.21 & 44.74 & 44.57 & 46.24 \\ High visual comfort & 25.57 & 31.08 & 41.40 & 50.56 & 75.15 \\ Low visual fatigue & 20.63 & 23.01 & 34.50 & 28.47 & 35.59 \\ \hline \hline \end{tabular} The unit of screen luminance is cd/m\({}^{2}\).  
\end{table}