Photo-Trichromatic Printing. Part I. The three fundamendal colour sensations.

Photo-Trichromatic Printing
C. G. Zander
Published by Raithby, Lawrence & Co., Ld., Leicester
1896The theory of the three fundamental colour sensations originated with Dr. Thomas Young in 1802, but was discredited and forgotten until 1853, when Prof. Helmholtz again brought it forward, and by his experiments added greatly to its probabilities. Soon after, J. Clerk-Maxwell first demonstrated pretty conclusively, by means of an ingenious contrivance of his own, called Maxwell's colour box, that there are really only three fundamental or primary colour sensations namely, red, green and violet.

If colours representing these three fundamental sensations are combined in proper proportions they form white light. Red and green combined form yellow. Green and violet combined make blue. Violet and red make purple, a colour not present in the spectrum.

Yellow (the combination of red and green) and blue (the combination of the violet and green) combined in proper proportions will also produce white light.

To call red, green and violet "primary" colours may seem strange to those who are used to the primary colours of the artists, namely, red, yellow and blue, and knowing what effects their various combinations will produce. However, what I have just stated about coloured light (for we are not now dealing with pigment-colours) can be proved, though perhaps not in the most strictly scientific way, by having three coloured circular glass slides to match, as nearly as possible, the red, green and violet of the spectrum. White light is projected throug-h these slides on to a screen by means of a lantern, and the coloured light discs moved until they partly overlap, as shown on the frontispiece. This experiment was shown upon the screen by Mr. F. E. Ives in his paper on the photochromoscope, read before the Royal Society of Edinburgh on January 17th, 1896. The outer parts of the circles will show the fundamental red, violet and blue, the centre where all three overlap will be white or probably slightly grey owing to the impure colouring of the glasses. Where the red and green overlap yellow will be shown, where green and violet overlap cyan-blue, and where violet and red overlap a kind of pale crimson or magenta.