Oldal 167 [167]
OCR
COLOURS IN RIPPLED WATER or surface entirely covered with minute spots of the constituent colours at a distance sufficient to cause them to blend completely in the eye. This system of mixing coloured lights on the canvas has advantages which would seem to recommend it for the painting of the whole surface of the rippled water. It not only gives increased luminosity, but also, as pointed out by Rood, adds a lustre and transparency not otherwise obtainable. “If the coloured lines or dots are quite distant from the eye, the mixture is of course perfect and presents nothing remarkable in its appearance; but before this distance is reached there is a stage in which the colours are blended, shall receive simultaneously blue and yellow light, not the slightest approach to green is produced, but a grey, slightly tinged with yellow. By carefully reducing and adjusting the portion of the yellow disc exposed it is possible to get rid of this yellowness and to obtain an absolutely neutral grey . . . The light reflected from a blue pigment, mingled with the light reflected from a yellow, invariably produces white of small brightness, that is, a neutral grey” (“Colour,” by Prof. A. H. Church, Cassell and Co., 1887, page 80). According to the Young-Helmholtz theory of colour-perception, now generally accepted, there are three primary colour sensations, viz., red, green and blue (or violet). The secondary colour-sensations arise from mixtures of two of these primaries; thus a mixture of red and green lights gives the sensation of yellow, green and blue together give that of sea green, and red and blue that of purple. A mixture of all three primaries in the right proportions gives white. The complementary of any given colour is that colour which must be added to it in order to produce the sensation of white. Thus yellow is the complementary of blue, purple of green, and sea green of red. For a complete account of Young’s theory and its developments, see Church’s manual on “Colour,” from which is taken the passage quoted above.
