A projection system comprising an information processing apparatus capable of processing image data and a projector capable of performing a display process on the image data processed by the information processing apparatus, when the bit number representing the number of gradations of pixel data transmitted from the information processing apparatus to the projector is n-bit and the bit number representing the number of gradations which can be expressed by the projector is m-bit (m>n). The image processing apparatus outputs image data where m-bit pixel data is divided into k-pieces of pixel data of at most n-bits, and the projector synthesizes the k-pieces of pixel data based on a set synthesis rule to generate the m-bit pixel data in the pixel.