The image processing system includes a scanner, a pixelated photon detector (PPD), and at least one processor. The at least one processor displays a setting screen on a display unit. The setting screen is a screen for setting an identification range that is a range of gradation to be identified. The at least one processor displays a second image obtained by converting a first image on the display unit. The second image is an image obtained by converting the first image based on at least the identification range. The first image is generated based on an intensity signal of light detected by a PPD and a scanning position by the scanner.