1. An image processing system including a plurality of image pickup apparatuses, an image processing apparatus, and an information processing apparatus, the image processing apparatus including: a memory that memorizes a plurality of pickup images in which each image pickup apparatus has picked up an object by varying an irradiation direction of a light, and each image pickup apparatus has picked up the object from a plurality of different angles; an extracting portion that extracts an area image of an area indicated by a user from each of the pickup images memorized in the memory; a calculating portion that calculates at least one illumination parameter for each area image by one of calculating an amount of edges from each area image extracted by the extracting portion, executing a clustering process to brightness of each area image extracted by the extracting portion, and executing a totaling process of totaling differences in brightness between the area images extracted by the extracting portion; and a generating portion that generates at least one synthetic image by synthesizing the area images extracted by the extracting portion with the at least one illumination parameter, the information processing apparatus including: a display that displays the at least one synthetic image generated by the generating portion; and a varying portion that varies the at least one synthetic image displayed in the display depending on one of a selected type of the plurality of image pickup apparatuses, a selected pickup angle of the plurality of pickup images, and the irradiation direction of the light.