PRCG Category    Count arch 295 game 41 nature 181 object 220 poeple 50 hybrid 13 Total 800 Table 6: The count of the PRCG in each category 2.  game - images from computer games. 3.  nature - images of natural scenery such as forest, plants, beaches, ponds and also general outdoor scene. 4.  object - images of objects such as books, tables, watches and so on. 5.  people - images of human, animal or insects. 6.  hybrid - images of combined computer graphics and camera images. Figure 4 shows the example images for the content categories within the PRCG  set. Table 6 shows the count for the PRCG of the different content category. 5   The Personal  Set The  Personal  set consists of two parts, i.e., 800 images from the authors' personal collections (Personal Columbia) and 400 images from the personal collection of Philip Greenspun (Personal Greenspun).  The reason for in- cluding images for Greenspun's collection is to increase the diversity of the Personal  set in terms of the image content, the camera models and the photographer styles. 5.1   The Personal Columbia  Set The list below describes the characteristics of the Personal Columbia  set: 1.  Reliable sources: The images are captured by the authors in order to ensure its reliable authenticity. These images are captured in New 13