In the paper some results of research on discomfort glare measurement are described. The idea of practical realization of this measurement in interiors on the basis of the analysis of the investigated room image is presented. To obtain the necessary geometric quantities the coordinates of proper pixels in the image and some parameters of the imaging system should be known. The luminance values are extracted after the analysis of the brightness distribution of calibrated image, which is registered by the pinhole digital camera. The most important properties of the camera, such as spectral sensitivity, linearity, noise and the influence of exposition parameters on the pixel brightness were investigated. After correcting the spectral sensitivity experiments in the laboratory and in the didactic room were conducted. In the laboratory test the error of the UGR measurement was lower - it reached 6,9%. Some possibilities of improving the accuracy of measurement are indicated.