# Which Features Are More Correlated to Illuminant Estimation: A Composite Substitute
## 4 Experimental Results
### Experiment B: Testing on Image Set from Identical Camera (Within Camera)
For the camera of Canon 5D, the composite of RGBuv+ChengSF+IIF has a 25.9% performance improvement in recovery AE Mean, and a 25.4% performance improvement in recovery AE Trimean, compared with WP. For the camera of Canon EOS 550D, the same improvements reach 42.3% and 32.3% (ours versus GGW), respectively. In our experiments, the optimal feature combination is RGBuv+ChengSF+IIF, which obtains outstanding performances compared with other feature selections. The combination of image features affects the illuminant estimation since the proposed method is to directly map the extracted features to illuminant color. Except for the results listed in Tables 3 and 4, we conducted many other experiments for the proposed method with more feature combinations. We find that it is not the more combined features the better performance. Just the correlated features are effective for illuminant estimation. Thus, it is significant to find which features are more correlated to the illuminant estimation. In this study, we just investigated several features and their combinations. From the experimental results given, there are reasons to believe that if we find more effective features, the performance can be even more improved by the proposed method. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Method**} & \multicolumn{8}{c}{**Recovery AE**} & \multicolumn{8}{c}{**Reproduction AE**} \\ \cline{2-13}  & **Mean** & **Med.** & **Tri.** & **B25\%** & **W25\%** & **Max** & **Mean** & **Med.** & **Tri.** & **B25\%** & **W25\%** & **Max** \\ \hline GW [4; 5] & 4.90 & 3.59 & 3.99 & 0.96 & 10.82 & 20.02 & 6.23 & 4.75 & 5.14 & 1.17 & 13.65 & 24.81 \\ WP [6] & 3.82 & 2.49 & 2.89 & 0.50 & 9.37 & 23.44 & 4.81 & 3.10 & 3.59 & 0.61 & 11.70 & 31.12 \\ SoG [7] & 6.34 & 3.89 & 4.72 & 0.76 & 15.56 & 35.75 & 7.16 & 4.89 & 5.69 & 0.92 & 16.73 & 25.69 \\ GE1 [8] & 5.89 & 4.08 & 4.69 & 0.75 & 14.00 & 32.43 & 6.74 & 5.20 & 5.69 & 0.89 & 15.41 & 27.41 \\ GE2 [8] & 6.43 & 3.83 & 4.66 & 0.92 & 16.05 & 37.27 & 7.18 & 4.77 & 5.64 & 1.06 & 17.15 & 31.32 \\ PCA-based [21] & 6.94 & 4.36 & 5.33 & 1.05 & 16.69 & 45.97 & 7.62 & 5.28 & 6.19 & 1.20 & 17.39 & 32.77 \\ GGW [8] & 4.11 & 2.51 & 2.96 & 0.52 & 10.23 & 28.60 & 5.15 & 3.16 & 3.82 & 0.64 & 12.75 & 40.59 \\ LSR [44] & 3.94 & 2.99 & 3.30 & 1.36 & 7.96 & 17.92 & 4.84 & 3.88 & 4.16 & 1.61 & 9.69 & **20.08** \\ \hline \hline \multicolumn{13}{c}{**Proposed**} \\ \hline ClrM & **2.32** & **0.68** & **1.24** & **0.00** & 7.20 & 16.46 & **3.23** & **0.84** & **1.66** & **0.00** & 10.23 & 44.45 \\ \(CM_{19}\) & 2.83 & 2.14 & 2.34 & 0.53 & 6.32 & **15.04** & 3.67 & 2.69 & 3.00 & 0.65 & **8.32** & 21.28 \\ \(CM_{34}\) & 3.06 & 2.28 & 2.45 & 0.58 & 6.74 & 14.88 & 4.14 & 2.96 & 3.20 & 0.70 & 9.49 & 35.81 \\ CDF & 8.49 & 1.54 & 2.19 & 0.00 & 29.92 & 179.08 & 9.87 & 1.63 & 2.66 & 0.00 & 34.39 & 178.91 \\ IIF & 3.00 & 2.12 & 2.32 & 0.73 & 6.80 & 25.02 & 4.00 & 2.56 & 2.95 & 0.82 & 9.53 & 42.86 \\ RGBuv & 2.97 & 2.17 & 2.27 & 0.58 & 6.84 & 51.56 & 4.14 & 2.67 & 2.91 & 0.73 & 10.10 & 112.29 \\ ChengSF & 3.23 & 2.21 & 2.48 & 0.60 & 7.57 & 30.31 & 4.35 & 2.88 & 3.23 & 0.71 & 10.62 & 38.42 \\ RGBuv+ChengSF & 2.85 & 2.15 & 2.23 & 0.57 & 6.51 & 33.46 & 4.08 & 2.72 & 2.88 & 0.69 & 10.05 & 115.51 \\ RGBuv+ChengSF+IIF & 2.83 & 2.08 & 2.18 & 0.57 & 6.51 & 39.05 & 4.02 & 2.68 & 2.86 & 0.68 & 9.90 & 116.17 \\ RGBuv+ChengSF+IIF+\(CM_{34}\) & 2.78 & 1.99 & 2.13 & 0.61 & **6.31** & 32.80 & 4.02 & 2.51 & 2.75 & 0.72 & 9.91 & 120.15 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparative performance metrics between the proposed method and some conventional methods for Canon 5D.