A method and apparatus for measuring light reflections of an object, comprising a light-source illumination-observation assembly, the assembly comprising: (A) an illumination unit comprising an illumination light source and illumination aperture stop being arranged to provide a confined luminous field, an illumination field stop (307) adapted to provide an illumination beam (305) of light from said confined luminous field, an collimating optical element (309) adapted to collimate said illumination beam and to provide an illumination field (313) on an object; (B) an observation unit comprising: at least one observation field stop adapted to provide an observation beam (306) comprising a ray boundary, at least one focusing optical element (309) adapted to focus said observation beam, an observation light receiver; and (C) at least one common optical element (309) arranged so that said illumination beam and said observation beam form an overlap therein; and (D) a unit separation stop (310) adapted to stop light from said illumination unit in reaching said observation light receiver of said observation unit; wherein said at least one observation field stops (308, 310, 311) comprises at least one limiting field stop (310) adapted to limit said ray boundary of said observation beam and to maintain said overlap of said illumination beam and said observation beam; a diffuser light-source assembly; and use thereof.