A system removes a light sensor artifact from a light sensor in a printer that is used to obtain reflectance measurements from test patterns printed on an image substrate. The system includes a print head for ejecting a plurality of pixels having a first single color in a test pattern onto an image substrate, a light source for illuminating the test pattern on the image substrate with a light, a light sensor for measuring reflectance of the first portion of the test pattern with reference to a light having a color that is non-complementary to the first single color of the test pattern, measuring reflectance of the first portion of the test pattern with reference to a light that is complementary to the first single color of the test pattern, and measuring reflectance of the second portion of the test pattern with reference to the complementary light, the second portion including an area that overlaps the first portion of the test pattern, and a sensor controller configured to scale the reflectance of the first portion measured with reference to the non-complementary light to minimize a difference between the reflectance of the first portion measured with reference to the complementary light and the reflectance of the second portion measured with reference to the complementary light in the overlapped area.