An innovative low cost method for measuring the hemispherical transmittance & reflectance of highly diffusive flat glass specimens is presented. The method is based on sampling the transmitted (reflected) radient exitance on the specimen surface illuminated by a thin collimated beam. The sampling is accomplished with a movable device, composed of a small integrating sphere & a photomultiplier tube. The hemispherical quantity is then evaluated by numerical integration of the sampled data. The proposed method allows evaluating the corrective factor for spectra measured with commercial spectrophotometers. Preliminary results on three commercial sand-blasted specimens are presented & compared with those achieved with a commercial spectrophotometer, a 1-meter integrating sphere equipment & a goniophotometer. In the case if the more diffusive sample, even the 1-meter sphere happens to be insufficiently large to give the correct values of hemispherical transmittance.
