Fig. 5 | Nature Communications

Fig. 5

From: Structural absorption by barbule microstructures of super black bird of paradise feathers

Fig. 5

The impact of viewing direction and illumination on the appearance of feathers. a Normal black Lycocorax back feather. b Super black Ptiloris breast feather with modified barbule arrays. Directional reflectance from ray-tracing simulations is plotted as a log-scale color gradient on orthogonal projections of the reflectance hemisphere under four different lighting conditions (i–iv). Concentric rings represent 22.5˚, 45˚, 67.5˚, and 90˚. Horizontal line separates proximal and distal viewing quadrants. Schematics show a cross-sectional view of the optical setup of each illumination. Reflectance hemisphere in gray, feather in black. Concentric gold band indicates the angle of light source, yellow lines show the path of incident light (subsequent path of reflected light not shown). For normal black Lycocorax, the darkest viewing quadrant varies with the direction of incident light (compare ii with iv), whereas super black Ptiloris shows a strong directional bias in which the distal viewing quadrant is the darkest under all lighting conditions. See Supplementary Fig. 9 for additional species

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