Fig. 9From: The impact of variable illumination on vegetation indices and evaluation of illumination correction methods on chlorophyll content estimation using UAV imageryBoxplot of the absolute value of Pearson correlation of each VI (scaling VIs, normalized VIs, ELM corrected VIs and Retinex corrected VIs) and SPAD values. The VIs of soybean was extracted from the orthomosaic captured under three illumination conditions (sunny, overcast, and variable illumination condition)Back to article page