In order to provide an image processing system and the like which can reduce calibration time, the image processing system comprises: a device profile storage section which stores ideal-environment-measurement data; a light separating section which derives output light data indicating output light from an image projecting section and ambient light data based on a difference between first and second viewing-environment-measurement data measured through a sensor, a projection-plane-reflectance estimating section which estimates a reflectance of a projection plane, based on the output light data and the ideal environment-measurement data; a sensing data generating section which generates viewing-environment-estimation data based on the reflectance, the ideal-environment-measurement data and the ambient light data; an LUT generating section which updates an LUT based on the viewing-environment-estimation data; and a correcting section which corrects image information based on the updated LUT.