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.