Part 5 (1/2)

_S_, DIFFUSING SCREEN, placed over front apertures, to evenly distribute the light.]

(66) When this numbered scale of values is familiar, it serves not only to describe light and dark grays, but the value of colors which are at the same level in the scale. Thus R7 (popularly called a tint of red) is neither lighter nor darker than the gray of N7. A numeral written above to the right always indicates _value_, whether of a gray or a color, so that R1, R2, R3, R4, R5, R6, R7, R8, R9, describes a regular scale of red values from black to white, while G1, G2, G3, etc., is a scale of green values.

(67) This matter of a notation for colors will be more fully worked out in Chapter VI., but the letters and numerals already described greatly simplify what we are about to consider in the mixture and balance of colors.

+Mixture of light hues with dark hues.+

(68) Now that we are supplied with a decimal scale of grays, represented by divisions of the neutral axis (N1, N2, etc.), and a corresponding decimal scale of value for each of the ten hues ranged about the equator (R1, R2,-- YR1, YR2,-- Y1, Y2,-- GY1, GY2,-- and so on), traced by ten equidistant meridians from black to white, it is not difficult to foresee what the mixture of any two colors will produce, whether they are of the same level of value, as in the colors of the equator already considered, or whether they are of different levels.

[Ill.u.s.tration: Fig. 10.]

(69) For instance, let us mix a light yellow (Y7) with a dark red (R3).

They are neighbors in hue, but well removed in value. A line joining them centres at YR5. This describes the result of their mixture,--a value intermediate between 7 and 3, with a hue intermediate between R and Y. It is a yellow-red of middle value, popularly called ”dark orange.” But, while this term ”dark orange” rarely means the same color to three different people, these measured scales give to YR5 an unmistakable meaning, just as the musical scale gives an unmistakable significance to the notes of its score.

(70) Evidently, this way of writing colors by their degrees of value and hue gives clearness to what would otherwise be hard to express by the color terms in common use.

(71) If Y9 and R5 be chosen for mixture, we know at once that they unite in YR7, which is two steps of the value scale above the middle; while Y6 and R2 make YR4, which is one step below the middle. Charts prepared with this system show each of these colors and their mixture with exactness.

(72) The foregoing mixtures of dark reds and light yellows are typical of the union of light and dark values of any neighboring hues, such as yellow and green, green and blue, blue and purple, or purple and red.

Next let us think of the result of mixing different values in opposite hues; as, for instance, YR7 and B3 (Fig. 11). To this combination the color sphere gives a ready answer; for the middle of a straight line through the sphere, and joining them, coincides with the neutral centre, showing that they _balance in neutral gray_. This is also true of any opposite pair of surface hues where the values are equally removed from the equator.

[Ill.u.s.tration: Fig. 11.]

(73) Suppose we subst.i.tute familiar flowers for the notation, then YR7 becomes the b.u.t.tercup, and B3 is the wild violet. But, in comparing the two, the eye is more stimulated by the b.u.t.tercup than by the violet, not alone because it is lighter, but because it is stronger in chroma; that is, farther away from the neutral axis of the sphere, and in fact out beyond its surface, as shown in Fig. 11.

The head of a pin stuck in toward the axis on the 7th level of YR may represent the 9th step in the scale of chroma, such as the b.u.t.tercup, while the ”modest” violet with a chroma of only 4, is shown by its position to be nearer the neutral axis than the brilliant b.u.t.tercup by five steps of chroma. This is the third dimension of color, and must be included in our notation. So we write the b.u.t.tercup YR 7/9 and the violet B 3/4,--chroma always being written below to the right of hue, and value always above. (This is the invariable order: HUE {VALUE/CHROMA}.)

(74) A line joining the head of the pin mentioned above with B 3/4 does not pa.s.s through the centre of the sphere, and its middle point is nearer the b.u.t.tercup than the neutral axis, showing that the hues of the b.u.t.tercup and violet _do not balance in gray_.

+The neutral centre is a balancing point for colors.+

(75) This raises the question, What is balance of color? Artists criticise the color schemes of paintings as being ”too light or too dark” (unbalanced in value), ”too weak or too strong” (unbalanced in chroma), and ”too hot or too cold” (unbalanced in hue), showing that this is a fundamental idea underlying all color arrangements.

(76) Let us a.s.sume that the centre of the sphere is the natural balancing point for all colors (which will be best shown by Maxwell discs in Chapter V., paragraphs 106-112), then color points equally removed from the centre must balance one another. Thus white balances black. Lighter red balances darker blue-green. Middle red balances middle blue-green. In short, every straight line through this centre indicates opposite qualities that balance one another. The color points so found are said to be ”_complementary_,” for each supplies what is needed to complement or balance the other in hue, value, and chroma.

(77) The true complement of the b.u.t.tercup, then, is not the violet, which is too weak in chroma to balance its strong opposite. We have no blue flower that can equal the chroma of the b.u.t.tercup. Some other means must be found to produce a balance. One way is to use more of the weaker color. Thus we can make a bunch of b.u.t.tercups and violets, using twice as many of the latter, so that the eye sees an _area_ of blue twice as great as the _area_ of yellow-red. Area as a compensation for inequalities of hue, value, and chroma will be further described under the harmony of color in Chapter VII.

(78) But, before leaving this ill.u.s.tration of the b.u.t.tercup and violet, it is well to consider another color path connecting them which does not pa.s.s through the sphere, _but around it_ (Fig. 12). Such a path swinging around from yellow-red to blue slants downward in value, and pa.s.ses through yellow, green-yellow, green, and blue-green, tracing a _sequence of hue_, of which each step is less chromatic than its predecessor.

[Ill.u.s.tration: Fig. 12.]

This diminis.h.i.+ng sequence is easily written thus,--YR 8/9, Y 7/8, GY 6/7, G 5/6, BG 4/5, B 3/4,--and is shown graphically in Fig. 12. Its hue sequence is described by the initials YR, Y, GY, G, BG, and B. Its value-sequence appears in the upper numerals, 8, 7, 6, 5, 4, and 3, while the chroma-sequence is included in the lower numerals, 9, 8, 7, 6, 5, and 4. This gives a complete statement of the sequence, defining its peculiarity, that at each change of hue there is a regular decrease of value and chroma. Nature seems to be partial to this sequence, constantly reiterating it in yellow flowers with their darker green leaves and underlying shadows. In spring time she may contract its range, making the blue more green and the yellow less red, but in autumn she seems to widen the range, presenting strong contrasts of yellow-red and purple-blue.

(79) Every day she plays upon the values of this sequence, from the strong contrasts of light and shadow at noon to the hardly perceptible differences at twilight. The chroma of this sequence expands during the summer to strong colors, and contracts in winter to grays. Indeed, Nature, who would seem to be the source of our notions of color harmony, rarely repeats herself, yet is endlessly balancing inequalities of hue, value, and chroma by compensations of quant.i.ty.

(80) So subtle is this equilibrium that it is taken for granted and forgotten, except when some violent disturbance disarranges it, such as an earthquake or a thunder-storm.