A reflectance photometer for quantitatively measuring diffuse light includes a light source located above a sample. The reflectance photometer also includes a first detector mounted at a preselected scattering angle relative to an axis extending perpendicularly from the sample through the light source. A first linear polarizer is mounted between the sample and the light source. The direction of polarization of the first linear polarizer is vertical to a scattering plane defined by the direction of incoming light from the light source and the direction of reflected light detected by the first detector. A second linear polarizer is mounted between the sample and the first detector. The direction of the second polarizer is parallel to the scattering plane. The reflectance photometer can include a second detector mounted at a second, scattering angle. A third linear polarizer is mounted between the sample and the second detector. The direction of polarization of the third linear polarizer can be perpendicular or parallel to the scattering plane. Generally, the three polarizers are close such that the contributors of scattered light as related to surface noise will be minimized for the first detector and maximized for the second detector, respectively. The optimum settings of the polarizer will depend on the settings of the polarizers, the scattering geometry, the sample orientation and the bulk and surface scattering properties of the sample material.