Fig. 3
From: Spatio-temporal and -spectral feature maps in photoplethysmography imaging and infrared thermography
Selection of feature maps of the adult measurement w/o movement: mean intensity is used as a visual reference. All dynamic maps show a noisy background pattern. The maps temporal variance and band mean power look very similar. Both allow the identification of static background elements, hinting at non-constant illumination conditions. Regarding spectral flatness, the static background is not visible which could be advantageous for image segmentation