1. An image projecting system comprising: a plurality of projector apparatuses that project images based on inputted image signals onto a screen so that the images are displaced relative to one another by a predetermined amount and superimposed; an observation apparatus that observes luminance of an image region composed of a plurality of projected images that have been projected onto the screen; and a control apparatus that supplies to the plurality of projector apparatuses the image signals in which a luminance value of each pixel that constructs an image to be projected by each projector apparatus has been adjusted based on an observation result of the observation apparatus, wherein the image region composed of the plurality of projected images is presented by superimposing a first projected image and a second projected image that has a higher resolution than the first projected image, the first projected image being based on minimum pixel values for the image region, and the second projected image being based on pixel values that represent differences from the minimum pixel values, wherein predetermined pixels in the image region are presented by superimposing corresponding pixels in the projected images from n adjacent projector apparatuses (where n is an integer of two or higher), wherein the plurality of projector apparatuses are arranged such that a width of a respective image projected by each of respective adjacent projector apparatus is equal to a multiple (x) of a distance between the adjacent projector apparatus, in which x is an integer of two or higher, wherein the image region composed of the plurality of projected images is formed of images projected by respective ones of four or more of the projector apparatuses, and wherein each of the images projected by the respective ones of the four or more of the projector apparatuses comprises a high-resolution image and a low-resolution image.