MIXTURE & BALANCE
41
PARTS.
C, Cabinet, with sample-holder (H) and mirror (M), which may be removed and stored to left of dial (D) when instrument is closed for transportation.
D, Dial records color values in terms of standard white (100), the opposite end of the scale being absolute blackness (o).
E, Eye-piece: to shield eye and sample from extraneous light while color determinations are being made. Fatigue of retina should be avoided.
G, Gear: actuates cat’s-eye shutter, which controls amount of light admitted to right half of instrument. Its shaft carries index-hand over dial.
H, Field-Holder: retains sample and standard white in same plane, and isolates them, is hinged upon lower edge, and secured by pivot clamp.
M, Mirror: permits observation of the isolated halves of the holder, bearing standard white and the color to be measured. Should be clean and free from dust on both sides of central partition.
S, Diffusing Screen, placed over front apertures, to evenly distribute the light.N5, as will also N7 and N3, N8 and N2, or N9 and N1. But N9 and N3 will unite to form N®, which is midway between 3 and 9.
(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 R’ (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.
