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  1. Maxwell, Trans. Roy. Soc. Edinburgh 21, 275 (1855).
    [Crossref]
  2. The symbols and terminology here employed and the data concerning the standard observer will be found in the Handbook of Colorimetry (Technology Press, Massachusetts Institute of Technology, Cambridge, Massachusetts, 1936).
  3. The terms red, green, and blue are adopted to facilitate the presentation and do not cause any sacrifice of generality. Those who are accustomed to think in terms of subtractive processes will find it useful to keep in mind that the conventional blue-green dye or pigment controls the amount of red light in the reproduction; the magenta (red) dye or pigment, the amount of green light; and the yellow dye or pigment, the amount of blue light. A method by which the primaries in a subtractive process may be identified is discussed in a later section.
  4. Although other sets of primaries can be found that will slightly increase the area of this triangle, the set selected has the advantage of permitting the reproduction of colors of high purity with dominant wave-lengths lying between 570 and 640 millimicrons. The colors of natural objects and also the colors produced with existing dyes and pigments commonly approach the spectrum locus more closely in this spectral region than elsewhere. It should be noted that the chromaticity diagram does not permit the representation of brightness. The gamut of attainable colors is actually a solid in which brightness is represented in a direction perpendicular to the plane of the diagram. For a complete representation of the attainable gamut, this solid must be constructed.
  5. Reference should be made in this connection to the early papers of F. E. Ives and the more recent work of Schaefer and Ackermann, Zeits. f. tech. Physik 8, 55–62 (1927).
  6. L. A. Jones, “Photographic Reproduction of Tone,” J. Opt. Soc. Am. 5, 232 (1921).
    [Crossref]
  7. The tristimulus values of the primaries and the values of K1, K2⋯K9 uniquely determine k1, k2⋯k9. If desired, the functions S1, S2, and S3 might be chosen in such a manner that some of the constants k1, k2⋯k9 are substantially zero.
  8. An alternative procedure is to determine the trichromatic coefficients by means of a colorimeter. In any event, the preparation of these test areas should be carried out under precisely the same conditions as those obtaining in the actual process of reproduction. This means that the test areas should be printed on the same paper stock, using the inks in the same order of progression. If the process is one in which a black plate is employed, the black impression should be made in preparation of each test area.

1927 (1)

Reference should be made in this connection to the early papers of F. E. Ives and the more recent work of Schaefer and Ackermann, Zeits. f. tech. Physik 8, 55–62 (1927).

1921 (1)

1855 (1)

Maxwell, Trans. Roy. Soc. Edinburgh 21, 275 (1855).
[Crossref]

Ackermann,

Reference should be made in this connection to the early papers of F. E. Ives and the more recent work of Schaefer and Ackermann, Zeits. f. tech. Physik 8, 55–62 (1927).

Jones, L. A.

Maxwell,

Maxwell, Trans. Roy. Soc. Edinburgh 21, 275 (1855).
[Crossref]

Schaefer,

Reference should be made in this connection to the early papers of F. E. Ives and the more recent work of Schaefer and Ackermann, Zeits. f. tech. Physik 8, 55–62 (1927).

J. Opt. Soc. Am. (1)

Trans. Roy. Soc. Edinburgh (1)

Maxwell, Trans. Roy. Soc. Edinburgh 21, 275 (1855).
[Crossref]

Zeits. f. tech. Physik (1)

Reference should be made in this connection to the early papers of F. E. Ives and the more recent work of Schaefer and Ackermann, Zeits. f. tech. Physik 8, 55–62 (1927).

Other (5)

The tristimulus values of the primaries and the values of K1, K2⋯K9 uniquely determine k1, k2⋯k9. If desired, the functions S1, S2, and S3 might be chosen in such a manner that some of the constants k1, k2⋯k9 are substantially zero.

An alternative procedure is to determine the trichromatic coefficients by means of a colorimeter. In any event, the preparation of these test areas should be carried out under precisely the same conditions as those obtaining in the actual process of reproduction. This means that the test areas should be printed on the same paper stock, using the inks in the same order of progression. If the process is one in which a black plate is employed, the black impression should be made in preparation of each test area.

The symbols and terminology here employed and the data concerning the standard observer will be found in the Handbook of Colorimetry (Technology Press, Massachusetts Institute of Technology, Cambridge, Massachusetts, 1936).

The terms red, green, and blue are adopted to facilitate the presentation and do not cause any sacrifice of generality. Those who are accustomed to think in terms of subtractive processes will find it useful to keep in mind that the conventional blue-green dye or pigment controls the amount of red light in the reproduction; the magenta (red) dye or pigment, the amount of green light; and the yellow dye or pigment, the amount of blue light. A method by which the primaries in a subtractive process may be identified is discussed in a later section.

Although other sets of primaries can be found that will slightly increase the area of this triangle, the set selected has the advantage of permitting the reproduction of colors of high purity with dominant wave-lengths lying between 570 and 640 millimicrons. The colors of natural objects and also the colors produced with existing dyes and pigments commonly approach the spectrum locus more closely in this spectral region than elsewhere. It should be noted that the chromaticity diagram does not permit the representation of brightness. The gamut of attainable colors is actually a solid in which brightness is represented in a direction perpendicular to the plane of the diagram. For a complete representation of the attainable gamut, this solid must be constructed.

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Figures (11)

F. 1
F. 1

Chromaticity diagram based on the I.C.I. standard observer and coordinate system. The dashed triangle indicates the color gamut obtainable with mixtures containing positive amounts of the homogeneous primaries R, G, and B, whose wave-lengths are 700, 535, and 400 millimicrons, respectively.

F. 2
F. 2

The functions Sr, Sg, and Sb represent the effective spectral sensitivities of the three emulsions to be used in making three color-separation negatives that will control properly the homogeneous primaries represented in Fig. 1.

F. 3
F. 3

Relative spectral energy distributions of three arbitrarily selected nonhomogeneous primaries.

F. 4
F. 4

The dashed triangle on this chromaticity diagram indicates the color gamut obtainable with mixtures containing positive amounts of the nonhomogeneous primaries R, G, and B, whose energy distributions are represented in Fig. 3.

F. 5
F. 5

The functions Sr, Sg, and Sb represent the effective spectral sensitivities of the three emulsions to be used in making three color-separation negatives that will control properly the nonhomogeneous primaries whose energy distributions are represented in Fig. 3.

F. 6
F. 6

Curves A and C together are identical with the Sr function shown in Fig. 5. The ordinates of curve B are the same as the corresponding ordinates of curve C with the signs changed.

F. 7
F. 7

Conventional characteristic curve for a typical photographic emulsion showing the density of the developed deposit as a function of the logarithm of the exposure.

F. 8
F. 8

Curve showing the transmittance of the developed deposit as a function of the exposure in the “underexposure” region.

F. 9
F. 9

Spectrophotometric curves illustrating a method for identifying the primaries in subtractive processes.

F. 10
F. 10

The functions Sr, Sg, and Sb represent the effective spectral sensitivities of the three emulsions to be used in making three color-separation negatives that will control properly the primaries identified in Fig. 9.

F. 11
F. 11

Spectrophotometric curves of three ideal dyes or pigments at full concentration.

Tables (3)

Equations (51)

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X = r X r + g X g + b X b ,
Y = r Y r + g Y g + b Y b ,
Z = r Z r + g Z g + b Z b .
X = 0 E x ¯ d λ ,
Y = 0 E y ¯ d λ ,
Z = 0 E z ¯ d λ ,
X = k X ,
Y = k Y ,
Z = k Z ,
Σ r = 0 E S r d λ ,
Σ g = 0 E S g d λ ,
Σ b = 0 E S b d λ .
r = k r Σ r = k r 0 E S r d λ ,
g = k g Σ g = k g 0 E S g d λ ,
b = k b Σ b = k b 0 E S b d λ .
k r X r 0 E S r d λ + k g X g 0 E S g d λ + k b X b 0 E S b d λ = 0 E x ¯ d λ ,
k r Y r 0 E S r d λ + k g Y g 0 E S g d λ + k b Y b 0 E S b d λ = 0 E y ¯ d λ ,
k r Z r 0 E S r d λ + k g Z g 0 E S g d λ + k b Z b 0 E S b d λ = 0 E z ¯ d λ .
k r X r S r + k g X g S g + k b X b S b = x ¯ ,
k r Y r S r + k g Y g S g + k b Y b S b = y ¯ ,
k r Z r S r + k g Z g S g + k b Z b S b = z ¯ .
x r S r + x g S g + x b S b = x ¯ ,
y r S r + y g S g + y b S b = y ¯ ,
z r S r + z g S g + z b S b = z ¯ .
S r = ( y g z b y b z g ) x ¯ + ( x b z g x g z b ) y ¯ + ( x g y b x b y g ) z ¯ ,
S g = ( y b z r y r z b ) x ¯ + ( x r z b x b z r ) y ¯ + ( x b y r x r y b ) z ¯ ,
S b = ( y r z g y g z r ) x ¯ + ( x g z r x r z g ) y ¯ + ( x r y g x g y r ) z ¯ ,
D = γ ( log Σ log i ) ,
D = log ( 1 / T ) .
T = ( i / Σ ) r .
Σ = c T .
T = ( i / Σ ) γ .
T = ( i / c ( i / Σ ) γ ) γ = k Σ γ · γ .
T = T 0 k Σ ,
T = T 0 k Σ .
T = T 0 ( 1 c k ) + c k 2 Σ .
T = k Σ .
T = T 0 k Σ .
Σ = c ( T A + T B ) .
T A = T 0 k Σ A ,
T B = k Σ B ,
T = ( 1 c k ) T 0 + c k 2 ( Σ A Σ B ) .
T = k ( Σ A Σ B ) .
I = k 1 Σ 1 + k 2 Σ 2 + k 3 Σ 3 .
r = k 1 Σ 1 + k 2 Σ 2 + k 3 Σ 3 ,
g = k 4 Σ 1 + k 5 Σ 2 + k 6 Σ 3 ,
b = k 7 Σ 1 + k 8 Σ 2 + k 9 Σ 3 ,
K 1 S 1 + K 2 S 2 + K 3 S 3 = x ¯ ,
K 4 S 1 + K 5 S 2 + K 6 S 3 = y ¯ ,
K 7 S 1 + K 8 S 2 + K 9 S 3 = z ¯ ,
K 1 = k 1 X r + k 4 X g + k 7 X b , K 2 = k 2 X r + k 5 X g + k 8 X b , K 3 = k 3 X r + k 6 X g + k 9 X b , K 4 = k 1 Y r + k 4 Y g + k 7 Y b , K 5 = k 2 Y r + k 5 Y g + k 8 Y b , K 6 = k 3 Y r + k 6 Y g + k 9 Y b , K 7 = k 1 Z r + k 4 Z g + k 7 Z b , K 8 = k 2 Z r + k 5 Z g + k 8 Z b , K 9 = k 3 Z r + k 6 Z g + k 9 Z b .