Apparatus ( 10 ) for measuring absolute specular reflectance of a surface of a sample ( 22 ) includes a sample holder ( 12 ), a light source ( 18 ) for transmitting an incident light beam ( 16 ) onto a surface of the sample ( 22 ) and a detector ( 26 ) for detecting a specularly reflected component of the incident light. The light source ( 18 ), sample holder ( 12 ) and detector ( 26 ) are mounted and operatively associate ( 14, 24, 28 ) to be relatively moveable to vary the angle of incidence of light ( 16 ) onto sample ( 22 ) and to correspondingly automatically vary the relative position of the detector ( 26 ) such that the angle of reflection equals the angle of incidence. In the absence of the sample ( 22 ) or upon removal of the sample holder ( 12 ), light ( 16 ) impinges directly onto detector ( 26 ) to directly allow measurement of the absolute intensity of the light beam ( 16 ) as a reference measurement. This avoids the need to use intervening optical components such as mirrors which may degrade over time. It also allows provision of a relatively simplified apparatus.
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