the  Personal Columbia  images are recorded.  RAW format image is the direct output from the CCD sensor and therefore can be used to generate images with different in-camera image processing operations such as white-balancing, sharpening, contrast adjustment and nonlin- ear transformation, as well as image compression. See Subsection 5.1.1 for more details. 8.  For evaluating the robustness of the classifier with respect to the computer graphics rendering techniques: When the al- gorithm of the classifier is known, adversarial attack specific to the algorithm can be designed to manipulate the output of the classifier. For example, if the classifier is known for recognizing PRCG by the high color saturation, attackers can reduce the color saturation of a PRCG such that it is classified as a photographic image. Due to the dependency of an adversarial attack upon the specific algorithm, it is hard for our dataset to meet the specific needs from evaluating the classifier robustness against such attack. 9.  For evaluating sensitivity to ambiguity in content and camera effects: In Personal Columbia set, there are images of artificial objects such as drawing, sculpture, wax figures, fake fruit for decoration, and so on.  In the  PRCG  set, we have images of natural scenes such as forest, ponds, seaside as well as images of building. Furthermore, the simulation of the camera effects such as the depth-of-field (DoF) effect in the PRCG also results in an ambiguity in terms of camera effects. 4   The PRCG  Set This section will describe the acquisition process of the 800 PRCG in our dataset. The following list shows the properties of the PRCG  set: 1.  Reliable Sources:  The images are downloaded from the profes- sional 3D artist websites on the Internet such as www.softimage.com, www.3ddart.org,  www.3d-ring.com  and so on. Unfortunately, there are websites where people submit photographic images and claim to be PRCG. One characteristic of these unreliable websites is that the sub- mitted PRCG are often from anonymous persons or by people identify themselves by nicknames. Therefore, we only download the trustable PRCG, submitted together with the creator's name, contact informa- tion. Table 1 shows the major online sources for the PRCG  set. 8