[2] Earlier attempts at such measurements, but based on much simpler technology, had been made in 1860 by the English physicist James Clerk Maxwell (1831–1879).

Using newly developed spectrophotometric equipment and modifications of the experimental procedure König and Dieterici published a more detailed paper in 1892, determining the "fundamental sensations" not only of subjects with normal color vision (trichromats) but also of dichromats and monochromats.

[3] With these measurements König provided evidence for the conjecture that the most common form of color blindness, dichromacy, is due to the absence of one cone type in the eye.

Averaged König functions were widely used in psychophysical color stimulus calculations until new data based on a slightly different method were determined by John Guild and William David Wright in 1920s, resulting in the recommendations of standard observer data by the International Commission on Illumination (CIE, German:Commission Internationale de l'Eclairage) in 1931.

After Helmholtz's death in 1894, König took on the task of completing preparations for the second edition of the former's Treatise on physiological optics (1896, German:Handbuch der physiologischen Optik)[9] to which he added a bibliography of vision consisting of nearly 8,000 titles.