This diploma thesis deals with the light intensity analysis of phosphorescence. In order to carry out the analysis we took photographs depicting of phosphorescent objects during the experiments. With the help of a computer programme it was possible to determine the pixel value of light intensity on these photographs. Furthermore, we empirically tested how the pixel values depend on the energy received by the camera. We took photographs of the same phosphorescent objects that had the same light emission characteristics, but were exposed to camera for various periods of time. The measurements of light intensity decay are analysed using two different models. Additionally, we analysed the colour structure of the photographs of the phosphorescent objects. In the theoretical part, the phenomenon of phosphorescence is described in detail.