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The brightness (d) inside the highlight region are also determined by interactions between a surface’s absorption/reflectance properties, 3D shape and the illumination field. For example, specular reflections from dielectric materials like plastic preserve the spectral content of incident light; hence they look tinted only if the prevailing illumination is itself coloured. By contrast, coloured metals affect the tint of reflected light. We refer to a – c as gloss cues and d – f as colour cues.

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