Disclosed are apparatus and methods for determining accurate optical property values of turbid media. In one embodiment, the method includes (a) providing a light source, having a first wavelength and a known illumination power, sequentially at a plurality of specific illumination positions on a first surface of the specimen； (b) for each specific position of the light source, obtaining light emission measurements from a second surface of the specimen that is opposite the first surface, wherein the light emission measurements are obtained for a plurality of surface positions of the second surface； and (c) for each specific illumination position of the light source at the first surface of the specimen, determining one or more optical properties for the specimen based on the specific illumination position of the light source, the first wavelength of the light source, the known illumination power of the light source, and the obtained light emission measurements for such each specific illumination position. The optical properties for the plurality of specific illumination positions of the light source are individually determined for each specific illumination position of the light source.
