Page:NBS Circular 553.djvu/14

 two-word name making five additional Munsell hues: yellow-red, green-yellow, blue-green, purple-blue, and red-purple. These ten are called the major hues and to each one is assigned, consecutively on the equator of the solid, ten divisions numbered from one to ten (see pages 31 to 34), giving a 100-point hue scale with each major Munsell hue placed at the middle of its 10-point spread, or at division 5, as 5R, 5YR, 5Y, 5GY, and so forth. In this way, there are 10 steps between each major hue indicating- graduated steps of hue around the hue circuit. Ten secondary Munsell hues are included in the system, namely: 10R, 10YR, 10Y and so on, one between each adjacent pair of major hues. These secondary hues fall on the number ten positions of each set of ten hue divisions. Therefore, each major Munsell hue is understood to be at division five whereas each secondary hue is understood to be at division ten of the preceding major hue. The Munsell Color Com- pany has now produced similar charts that come at 2.5 and 7.5 or midway between each pair of adjacent primary and secondary charts [13]. Each of these charts consists of colored rectangles all of the same Munsell hue arranged in rows and columns, light colors near the top of the chart, dark near the bottom, grayish colors to the left and strong to the right.

The Munsell scale of value exhibits 10 visually equal steps ranging between black (represented by the notation N 0/) and white (N 10/), the intermedi- ate chips being dark to light grays. The Munsell value of a color is the same as that of the gray sample in the same row of the constant-hue charts, and is recorded in front of a shilling mark, thus 6 value is written 6/.

Munsell chroma is the degree of difference of a color from a gray of the same value and is indicated by steps numbered outward from the neutral axis. Therefore all samples in any vertical column of the constant-hue charts have the same Munsell chroma. Munsell chroma notations follow the shilling mark, thus 2 chroma is written /2. Colors of one Munsell hue are therefore represented in the solid by points falling in a single one of the vertical planes inter- secting at the black-white axis. Colors of one value are represented by points in any one horizontal plane; and colors of one chroma are represented by points in any one of the series of right circular cylin- ders concentric about the black-white axis.

The complete notation is written in the order: Hue Value/Chroma or H V/C with a space between the H and the V/C; for example, 5R 6/3 means a red of value 6 and chroma 3, and 6YR 6. 8/6. 6 means a yellow-red (orange) of value 6.8 and chroma 6.6 whose hue departs from the 5YR chart toward the 7.5YR chart by two-fifths of the hue difference between those charts.

4.2. Basic Plan of Forming the Designations

The hue name of the color designation is intended to indicate a range of hue represented by an angle around the neutral axis in the color solid, and other words in the designation are to indicate ranges of value and chroma for this hue range. The system of modifiers is indicated in figure 2 together with the

CD

white

-C

5

J c 

T

very pale

very light

>

O

cp >.

>*

a

CP >

(v. p.)

(v.l.)

brilliant

£ — o>

light -i

(1. — i si

pale

(p.)

light

(brill.)

>

o

CP

e>

a >

5.^

light grayish (1. gy.)

(1.)

mediurr

(med

-ish

(-ish

grayish

m ode rate

stron g

gray

Gy.)

sh gray

h Gy.)

(gy.)

(m.)

(s.)

dark

(d.

dark -i:

(d.-is

dark grayish (d. gy.)

dark

(d.)

deep

black (Bl.)

-ish black (-ish Bl.)

blackish

(bl.)

very dark (v.d.)

very deep (v. deep)

Soturotion (Munsell Chroma)

Figure 2. Scheme of the hue modifiers, the “-ish” grays and the neutrals with their modifiers.

Abbreviations are given in parentheses.

approved abbreviations. Deviations from the mod- erate range in value are indicated by the terms light and dark; deviations in chroma by the terms grayish, strong and vivid; and deviations in both by the terms light grayish or pale, dark grayish, black- ish, brilliant and deep The whole color designa- tion, hue name and modifiers, therefore defines a block of the color solid bounded by vertical planes of constant hue, horizontal planes of constant value, and cylindrical surfaces of constant chroma. The color solid is divided into 262 such blocks including the grays and “-isli” grays with 5 cylindrical blocks for black, grays, and white making 267 color-name blocks in all.

4.3. Divisions of the Hue Circle

The 1933 recommendations by I. H. Godlove in- cluded a 20-point division of the hue circle for colors of moderate saturation, a 10-point division for weak colors and a 5-point division for very weak colors. These recommendations were followed closely at first with the thought that each color designation should refer to about the same fraction of the Mun- sell hue circuit. However, it was soon evident that deviations from this plan were necessary to make the designations accord with usage at that time in the National Formulary and the United States Pharmacopoeia, and more recently with usage in the textile industries and by the general public. Most of these improvements were achieved by intro- ducing the terms pink, orange, brown, and olive

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