A projection system, apparatus, and method in which a plurality of projectors project images to form an image as a whole on a projected area which is a screen area on which a content image is projected without a frame. Images for calibration are output by the plurality of projectors, the images for calibration including positioning markers that are indications for positioning to the corners of the projected area. Correction coefficients are calculated based on reference points of the projected area, and a projection target area is defined which corresponds to the screen area.