Fig. 5
From: Spatio-temporal and -spectral feature maps in photoplethysmography imaging and infrared thermography
Similarity maps of the selection of feature maps of the adult measurement w/o movement: the mean intensity maps are not very uniform. The IRT map highlights the subjects silhouette, while the head is recognizable in the PPGI maps. The temporal variance and band mean power maps are less clear for all bands than the corresponding spectral flatness maps. The VIS maps especially suffer from an uneven distribution (left and right image halves have different histograms)