Relationship between facular intensity contrast and μ. Panels (a)–(h) show pixels grouped by their associated B_LOS/μ values. Points represent the mean intensity contrast in μ bins of width 0.03; shaded areas indicate the standard deviation within each bin. Orange dots correspond to a single-viewpoint analysis using SDO/HMI data from the full disc. Green triangles represent results from the dual-viewpoint approach, combining SO/PHI-HRT observations at the disc centre with SDO/HMI observations near the limb in the region of overlap. Note that the y-axis limits differ between panels.