A goniophotometer (100) comprises a light source (1) which transmits light through an aperture (2) onto a linear photodetector array (6). The width of the aperture (2) is substantially of the same order of magnitude as the width of an individual photodetector in the photodetector array (6). In a preferred embodiment, the width of the aperture (2) is substantially twice the width of an individual photodetector in the array (6).
