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A Concise History of the Chromaticity DiagramA Concise History of the Chromaticity Diagram
from Newton to the CIE from Newton to the CIE Standard Colorimetric Standard Colorimetric Observer Observer
Claudio OleariDipartimento di FisicaUniversità di [email protected]
CREATE 2010, Gjøvik
I am not an historian
(but I like History) !
warningAll phenomena that follow hold true
for colour matching in
aperture mode.
!
The protagonists
1623 - Galilei
1704 - Newton
1802 - Young
1808 - (Göthe)
1852 - Helmholtz
1853 - Grassman
1857 - Maxwell
1872 - Hering
1920 - Schrödinger1931 ...
The historical steps
centre of gravity rule
three kind of photoreceptors (fibres)
tristimulus: colour measure in ZERO ORDERZERO ORDER approximation
The standards CIE 1931-CIE 1964-CIE 1976The standards CIE 1931-CIE 1964-CIE 1976OSA-UCS system (1947-1974)
“Colour Appearance”: towards the colour measure in FIRST ORDERFIRST ORDER approximation
(Göthe against Newton)
Helmholtz-Hering Controversy
trichromacy trichromacy Le Blom, Palmer
Indeed, rays, Indeed, rays, properly expressed, properly expressed, are not coloured.are not coloured.
(Isaac Newt(Isaac Newton) on)
Any colour computation needs colour Any colour computation needs colour measurement.measurement.
But But ColourColour is a sensationis a sensation..
Then the question:Then the question:
Can colour be measuredCan colour be measured??
COLOUR IS SUBJECTIVE.
This could induce us to deny a priori the colour measurement. On the contrary, colour can be measured because generally different persons agree in the judgment of the metameric colour matching, i.e. they affirm that different physical radiations appear equal.
(The comparison of the colour sensations among different individual observers is not required and the measurement of colour sensations is transformed into the physical measurement of the luminous radiations, which induce equal colour sensations in the normal observers.)
A correspondence between luminous radiations and colour sensations is realised, consequently the colour is indirectly measured by measuring the luminous radiation.
?
colour matching in bipartite field
R+G+B
?
B
G
R
?
Isaac Newton
New theory about light and colour (1671)
Opticks (1704)
Franco Giudice Ed., Isaac Newton, Scritti sula luce e sul colore, BUR, 2006
EXPERIMENTUM CRUCIS (1671)EXPERIMENTUM CRUCIS (1671)
No individual ray, no single refrangibility, is corresponding to white.
White in a heterogeneous mixture of differently refrangible rays.
ADDITIVE SYNTHESIS OF SPECTRAL LIGHTSADDITIVE SYNTHESIS OF SPECTRAL LIGHTS
2 f 2 f
CENTER OCENTER OFF GRAVITGRAVITYY RULERULE
Light Orange colour
CENTER OF GRAVITCENTER OF GRAVITY Y RULERULE
R Y
ry
Barycentric Coordinates and mixing Barycentric Coordinates and mixing colour lights colour lights
balance scales
2 2
R r
Y y
brg
(R,G,B)B
R
G
rg b
Chromaticity Diagram r = R/(R+G+B) g = G/(R+G+B) b = B/(R+G+B)
Barycentric CoordinatesBarycentric Coordinates
Barycentric Coordinates and mixing Barycentric Coordinates and mixing
independent colour lights33
: : : :R G B r g b
Three lights are independent if none of these lights is matched
by a mixture of the other two lights.
Barycentric Coordinates and mixing Barycentric Coordinates and mixing 44
independent (?)independent (?) colour lightscolour lights
Can we use a three dimensional yoke in a four Can we use a three dimensional yoke in a four dimension spacedimension space
NO!NO! Because Because four independent four independent colours are not existing!!colours are not existing!! TRICHROMACY TRICHROMACY
??
CENTER OF GRAVITCENTER OF GRAVITY Y RULERULE
constraint among spectral lights METAMERISMMETAMERISM
TRICHROMATIC COLOR RIPRODUCTION TRICHROMATIC COLOR RIPRODUCTION & REAL PRIMARIES& REAL PRIMARIES
R
B
G
An RGB system cannot reproduce all the real colours!An RGB system cannot reproduce all the real colours!
Instrumental reference frame
B
G
Negative light source!?!?
CB + G R = C ?????B + G = R + C
Phenomenon explained by Maxwell 180 years later
R
B
G
B + G R = C ?????B + G R + C = Q
C
METAMERISMMETAMERISM
R
Q
… it is such an orange as may be made by mixing an homogeneal orange with a white in the proportion of the line OZ to the line ZY, ... I. Newton
METAMERISMMETAMERISM
… it is such an orange as may be made by mixing an homogeneal orange with a white in the proportion of the line OZ to the line ZY, this proportion being NOTNOT of the quantities of mixed orange and white powdersmixed orange and white powders, BUTBUT the quantities of the lights reflected lights reflected from them. I. Newton
COMPLEMENTARY COLOURS ?!?!?COMPLEMENTARY COLOURS ?!?!?
COLORI COMPLEMENTARICOLORI COMPLEMENTARICOLORI COMPLEMENTARI ?!?!?COLORI COMPLEMENTARI ?!?!?COMPLEMENTARY COLOURS ?!?!?COMPLEMENTARY COLOURS ?!?!?
The existence of pairs of spectral lights that can be mixed to match white (complementary spectral lightscomplementary spectral lights) was not securely established until the middle of 1800.
White presented an especial difficulty for Newton, who wrote: (1671) - “There is no one sort of rays which alone can exhibit this [i.e. white]. This is ever compounded, and to its composition are requisite all the aforesaid primary colours.” (1704) - “if only two of the primary colours which in the circle are opposite to one another be mixed in an equal proportion , the point Z shall fall upon the centre O and yet the colour compounded of these two shall not be perfectly white, but some faint anonymous colourfaint anonymous colour. For I could never yet by mixing only two primary colours produce a perfect white. Whether it may be compounded of a mixture of three taken at equal distance in the conference.”
Christian Huygens: (1673) – “two colours alone (yellow and blueyellow and blue) might be sufficient to yield white.”
Newton’s mistake Newton’s mistake and open problems:and open problems:
1)1) angular position of the spectral lights angular position of the spectral lights ((Primary ColoursPrimary Colours) on the colour circle are ) on the colour circle are in relation to the in relation to the musical notes musical notes and not to and not to the colour complementaritythe colour complementarity
2)2) all the all the MagentaMagenta hues are represented by a hues are represented by a point in the colour circlepoint in the colour circle
3)3) Circular shapeCircular shape is only an approximation is only an approximation
four independent colours four independent colours are not existing!!are not existing!! TRICHROMACY TRICHROMACY
ADDITIVE MIXING OF COLOURED LIGHTSADDITIVE MIXING OF COLOURED LIGHTS
R
B
G
R
G
B
rgb
Grundig television
SUBTRACTIVE MIXING OF COLOURS SUBTRACTIVE MIXING OF COLOURS in screen plate printingin screen plate printing
CYANYELLOW
MAGENTA
BLUEGREEN
RED
BLACK
WHITE
Demichel (1924) – Neugebauer (1937)Demichel (1924) – Neugebauer (1937)Additive mixing of 8 colour lightsAdditive mixing of 8 colour lights
Demichel (1924) – Neugebauer (1937)Demichel (1924) – Neugebauer (1937)Additive mixing of 8 colour lightsAdditive mixing of 8 colour lights
TRICHROMACY of colour mixture: TRICHROMACY of colour mixture:
impalpable trichromacy impalpable trichromacy ↔ ↔ ↔ ↔ material trichromacymaterial trichromacy
- TRICHROMACY- TRICHROMACYand development of and development of three-colour reproductionthree-colour reproduction
- TRICHROMACY - TRICHROMACY in opposition to Newton’s opticsin opposition to Newton’s optics
Towards the definition of imaginary primaries
1757 – Mikhail Vasil’evich Lomonosov1777 – George Palmer1780 – John Elliot MD1802 – Thomas Young(1840 – David Brewster)
REAL & IMAGINARY PRIMARIESREAL & IMAGINARY PRIMARIES
Z
Y
X
George Palmer George Palmer (1777)(1777)
• Young’s contribution to understand Newton’s theory
• Light is a wave phenomenon
• Understanding of the light interference phenomenon
• Trichromacy related to three kinds of “fibres” in the retina, differently resonating if crossed by light
• Rotating disk for mixing colours (Claudius Ptolomaeus ≈100 – 175)
Thomas YoungThomas Young (1802)(1817)(1802)(1817)
Hermann von Helmholtz
(1852)(1855)(1866)
-- complementary colourscomplementary colours- magenta hues- magenta hues- chromaticity diagram- chromaticity diagram
REAL SPECTRAL PRIMARIESREAL SPECTRAL PRIMARIES
IMAGINARY PRIMARIESIMAGINARY PRIMARIES
Colour-Matching Functions in fundamental reference frame
R
V
A
- fundamental reference frame- imaginary primaries
James Clerk Maxwell
(1857)
Dpt Exp.Psychology, Cambridge University
Check of Newton’s centre of gravity rule
R
B
G
trilinear mixing triangle (c.1860)
Red
Green
Blue
Instrumental reference frameRed-Green-Blue real primaries
Fundamental reference frame imaginary primaries
)(b)(g
)(r
(K = Katherine)
Colour-matching functions in instrumental reference frame
CIE 1931 observer
Colour-Matching Functions:
Maxwell’s minimum saturation Method
R = 630.2 nm (rosso) G = 525.1 nm (verde) B = 456.9 nm (blu)
Colour matching of two beamsColour matching of two beams
Helmholtz-Hering controversy
(1872)
Ervin Schrödinger
(1920)
- fundamental reference frame,- “Helligkeit” equation and Alychne - tristimulus space metrics
- Hering’s chromatic opponencies
Ervin Schrödinger (1920)
tristimulus space and fundamental reference frame
Chromaticity diagram
König’s Colour-matching functions or König’s fundamentals
Lv=eRR+eGG+eBB
Exner’scoefficients
(R, G, B) (eR, eG, eB)
Schrödinger’s “Helligkeit” equation
LUMINANCE
towards the Colourimetric Standard Observer CIE
1931
X
Y
Z alychnealychne
700
400
500
600
)(z
Standard Colourimetric Observer CIE 1931Standard Colourimetric Observer CIE 1931
(D. B. Judd introduced the Schroedinger’s alychne)
)(x
)()( Vy
alychnealychne
From Newton to From Newton to SchSchrrödidinger & Juddnger & Judd
q1 q2q
W1 W2
q1q2
q
Alychne
( , )
( , )
q
q
x y
x y1 1 1
2 2 2
( , ) ,
x W x W y W y Wx y x y
W W W W1 1 2 2 1 1 2 2
1 2 1 2q
CENTER OF GRAVITCENTER OF GRAVITYY RULE RULE
Newton 1671 (1704) CIE 1931
CENTER OF GRAVITCENTER OF GRAVITYY RULE RULE
Thank you for your kind attention
Claudio Oleari
König’s Colour-matching functions or König’s fundamentals
Chromaticity diagram
tristimulus space and fundamental reference frame