8/19/2019 Ostwald and the Sistem of Color
1/50
Ostwald and the Theory of Colors
Jan J. Koenderin ! Physics & Astronomy, Universiteit Utrech"
8/19/2019 Ostwald and the Sistem of Color
2/50
Ostwald!s Basic Contributionsto Colorimetry are:
the spectrum & the color circle " semichromes #
the mensuration of the color circle
the structure of the object color solid
the colorimetric color atlas
color & spectral signature
8/19/2019 Ostwald and the Sistem of Color
3/50
The Spectrum
&the Color Circle
8/19/2019 Ostwald and the Sistem of Color
4/50
Newton demonstrates the spectrum (George Romney)
8/19/2019 Ostwald and the Sistem of Color
5/50
Newton’s spectrum had a resolution of only about 50-100nm(but the colors were almost perfect!).Newton saw 7(!) colors and fitted a musical scale to them.
8/19/2019 Ostwald and the Sistem of Color
6/50
Newton drew up a color circle (right), he probably emulatedDescartes’ representation of the musical octave (left).He somehow managed to let the spectrum “bite its own tail”,confusing the scientific world for over a century (till
Maxwell’s & Helmholtz’s experiments).
8/19/2019 Ostwald and the Sistem of Color
7/50
B G RC Y
R
YG
C
B M
Newton’s spectrum is
“not complete”:Only the painter’s“color circle”contains all hues.
It remained forOstwald to clear up
the relation betweenthe spectrum andthe color circle.
8/19/2019 Ostwald and the Sistem of Color
8/50
Newton thought he “proved” whitelight to be a “confused mixture of
homogeneous lights”. Goethe (Farbenlehre) showed thatcomplementary apertures yieldcomplementary images (Babinet’s
Principle) and produced the “invertedspectrum”.
spectrum
invertedspectrum
Neither the spectrum, nor the inverted spectrum are complete.
Goethe had trouble with green, Newton with purple.
8/19/2019 Ostwald and the Sistem of Color
9/50
Goethe experimented with
complementary apertures.He came to consider colors as mixtures of edge colors(“Kantenfarben”). This let to Schopenhauer’s notion
of colors as parts of daylight.
8/19/2019 Ostwald and the Sistem of Color
10/50
Goethe’s “edge colors” are obtained as thecumulated spectra (starting at either spectrumlimit) of the spectrum of the illuminant (“whitelight”, “daylight”). You see these colors when you look at a light/dark edge through a prism.
edge colors (”Kantenfarben”)
8/19/2019 Ostwald and the Sistem of Color
11/50
Schopenhauer (Über das Sehnund die Farben) noticed that there
exist exactly two best bipartitionsof daylight.
The cut locus is at the “antipodes”
of the spectrum limits.
The Goethe edge colors as
“parts of daylight” (cumulated
spectra from either spectrum
limit).
8/19/2019 Ostwald and the Sistem of Color
12/50
The cardinal colors as “parts of daylight”
8/19/2019 Ostwald and the Sistem of Color
13/50
Ostwald also thinks of the full colors as “parts of daylight”.Indeed the semichromes are “half of daylight”. Because hecurved the spectrum the purples appear as “natural parts”.Unlike Newton Ostwald retains the “gap”.
8/19/2019 Ostwald and the Sistem of Color
14/50
0 0.5 1 1.5
0
.2
.4
.6
.8
1
Ostwald’s “full colors” havemaximum color content for a given
hue.The band limits have to be atcomplementary wavelengths inorder to obtain the maximum.
Helmholtz decomposition
monochromatic
component
spectral width
8/19/2019 Ostwald and the Sistem of Color
15/50
Ostwald’s
“semichromes”
The relation between the color circle and the spectrumis explained through Ostwald’s construction of the“semichromes”. The semichromes are also full colors.
8/19/2019 Ostwald and the Sistem of Color
16/50
The Mensuration
of theColor Circle
8/19/2019 Ostwald and the Sistem of Color
17/50
The color circle is only a topological circle, without ametric. One would like to fit it with a “well temperedscale”. Ostwald pioneered a method to do this.
8/19/2019 Ostwald and the Sistem of Color
18/50
Ostwald’s “Principle of InternalSymmetry” is very simple: Define
bisection of line elements throughequal mixture.
Here the RGB color circle ismensurated: Starting with theprimary colors R, G and B, oneobtains the secundary colorsC, M and Y. Going the otherway one obtains C, M and Yfrom R, G and B. The whole
system is internally consistent.
8/19/2019 Ostwald and the Sistem of Color
19/50
Ostwald’s “Principle ofInternal Symmetry” yields anaffinely invariant arc lengthparameterization of thecolor circle.
The first colorimetric(numerical) calculationswere by Bouma in the1940’s (now forgotten).
8/19/2019 Ostwald and the Sistem of Color
20/50
Left an example of the mensurated color circle byOstwald. Right a mensurated color circle calculated(using the CIE 1964 standard observer) from moderndata for average daylight (CIE D75).
380 nm
450 nm
470 nm
480 nm
490 nm
500 nm
510 nm
520 nm
530 nm
540 nm
550 nm
560 nm
570 nm
580 nm
590 nm
600 nm
620 nm
660 nm
8/19/2019 Ostwald and the Sistem of Color
21/50
Coloroid 48 step scale
450
460470
480
490500
510520
530540
550
560
570
580
590600
DIN 24 step scale
450460
470
480490
500510
520530
540550
560
570
580
590600
610620
Munsell 40 step scale
370380390400410420430440450460470
480
490
500
510
520530540550
560
570
580
590600610620630
Empirically, the Ostwald mensuration “predicts” the
eye measure scales quite well. This is most remarkablebecause it requires mere colorimetric (objective) data.(Only judgments of equality, no absolute color
judgments!) Psychology is not involved.
Psychological (“Eye Measure”) Scales
8/19/2019 Ostwald and the Sistem of Color
22/50
The Structure of theObject Color Solid
8/19/2019 Ostwald and the Sistem of Color
23/50
Lambert 1772
Of the many attemps to
systematize the objectcolors before Runge (1834)none came up with the
correct topology.
The modern theory of the
color solid is due to ErwinSchrödinger (Ann.Physik1920).
8/19/2019 Ostwald and the Sistem of Color
24/50
PhilipOttoRunge
8/19/2019 Ostwald and the Sistem of Color
25/50
Runge came up with
the first “color solid” ofthe correct topology.(“Farbenkugel”, 1834)
8/19/2019 Ostwald and the Sistem of Color
26/50
The Schrödinger
“color solid”.
All object colors lie within a finite, convex volume. Itsboundary is smooth, except for two points: At theblack point the solid is tangent to the spectrum cone,at the white point to the inverted spectrum cone.
8/19/2019 Ostwald and the Sistem of Color
27/50
bandgap (non-spectral)
bandpass (spectral)lowpass edge color highpass edge color
black (monochromatic)off-white
The Schrödinger “optimal colors” make up the boundaryof the color solid. They are the brightest colors for any
given chromaticity (the best paints, containing no gray).
The most colorful optimal colors are the Ostwald full
colors.
8/19/2019 Ostwald and the Sistem of Color
28/50
Schrödinger’s color solid
mensurated via Ostwald’s“principle of Internal Symmetry”: A fully objective framework.
8/19/2019 Ostwald and the Sistem of Color
29/50
Ostwald conceived of object colors as partitivemixtures of white, black, and a full color. Placing the gray axis perpendicular to the center of the(full-)color circle, he arrived at a double cone.
8/19/2019 Ostwald and the Sistem of Color
30/50
example ofan Ostwaldatlas doublepagecomputedfor the RGB
colors
8/19/2019 Ostwald and the Sistem of Color
31/50
This atlas is
based on a24 hue colorcircle.
Notice theidiosyncratic
hue namesassigned byOstwald.
8/19/2019 Ostwald and the Sistem of Color
32/50
In the Schrödinger color solid the Ostwald full colors
(“Vollfarben”) are at greatest distance from the gray axis.
black pole
white pole
ribbon of full colors
not a planar “color circle!
8/19/2019 Ostwald and the Sistem of Color
33/50
A B
C
D
white
black
ultimate color
(virtual)
full color
The Ostwald atlas covers only part (A) ofthe object colors (A+C+D) as derived by
Schrödinger (1920).
By variation of the spectrum ofthe illuminant region B is available.
The colors in region C are “super-tints”(negative black content), those in regionD are “super-shades” (negative white
content).
8/19/2019 Ostwald and the Sistem of Color
34/50
0 8 16 24
0 %
50 %
100 %
In terms of the ultimate colors the full colors themselvescan be analyzed in terms of their color, white and blackcontent! The “best” colors are blue and yellow, “worst”
are cyan and magenta.
8/19/2019 Ostwald and the Sistem of Color
35/50
The ColorimetricColor Atlas
8/19/2019 Ostwald and the Sistem of Color
36/50
Albert Munsell (a painter)worked on a “color atlas”
almost simultaneously withOstwald. (The two met.)
In the final instance, Munsellreverted to “eye measure” toarrive at a metric.
Thus the “Munsell-system”stands well apart from
colorimetry proper.
Albert Munsell
8/19/2019 Ostwald and the Sistem of Color
37/50
Munsell’s concept of
a “color tree” is acylindrical coordinatesystem based on
the gray axis.There is no fundamentallimit to the distance the
“branches” may go.This fully ignores thecolorimetric basis.
8/19/2019 Ostwald and the Sistem of Color
38/50
Construction of a page of the Ostwald atlas. Thesamples can be generated by simple means (Ostwaldused the POMI, HASCH and inverted spectroscope).
This (in principle) involves NO EYE MEASURE.
8/19/2019 Ostwald and the Sistem of Color
39/50
Gelb - Kress
Kress
Rot - Kress
Rot - Veil
Veil
Ublau - Veil
Ublau - Eisblau
Eisblau
Seegrn - Eisblau
Seegrn - Laubgrn
Laubgrn
Gelb - Laubgrn
Ublau
12
Ublau 850, 25, 25
8/19/2019 Ostwald and the Sistem of Color
40/50
By far the best wayto memorize, select,
or indicate colors isby way of their hueand color, white and
black contents.
With some practice
one learns to “see”these parameters.
Modern application: “Color Pickers”
8/19/2019 Ostwald and the Sistem of Color
41/50
In Ostwald’s double cone the pages (full color-white-black triangles) are bound at the gray axis to a“periodic” book (no need for front or back covers).
8/19/2019 Ostwald and the Sistem of Color
42/50
Although Ostwald used empirical methodsto find suitable pigments, his color atlas isfirmly founded on colorimetric principles
(NOT eye measure!) and can be computed(and shown on the computer screen) fromstandard colorimetric tables.
It is different in kind from Munsell’s system.
8/19/2019 Ostwald and the Sistem of Color
43/50
Color
&Spectral Signature
8/19/2019 Ostwald and the Sistem of Color
44/50
2.0 2.5 3.0 eV
0
0.25
0.5
400500600700 nm
Reflectance spectra ofnatural materials (such asskin) can be captured verywell through Ostwald’sscheme, at least for
colorimetric purposes.
8/19/2019 Ostwald and the Sistem of Color
45/50
Ostwald asked a physicist: “What is the best recipe for yellow paint?” The answer was “zero reflectance
thoughout the spectrum except at 580 nm”.Ostwald noticed that this will produce a BLACK paint!
Ostwald looked at spectral reflectance of actual goodpaints and noticed that yellows reflect half of thespectrum! There are no “monochromatic” object
colors.
8/19/2019 Ostwald and the Sistem of Color
46/50
white content
color content
black content
complementary wavelengths
• Ostwald schematized spectral signatures in terms ofpartitive mixtures of spectral reflectances: Black, white and
a full color. This cuts down the!
degrees of freedom to amere 3! For colorimetric purposes this suffices.• Ostwald proposed to cut down the spectrophotometry toa determination of full color # and CWK contents.
black
color
white
8/19/2019 Ostwald and the Sistem of Color
47/50
Actual spectral signatures are not of the idealOstwald type (although often not too different).Thus the simple methods pushed by Ostwald will failto characterize spectral signature completely.
Ostwald was evidently aware ofthis but failed to stress the point. Although Ostwald’s methods are
not exact they are often very good approximations and quiteuseful when applied wisely.
8/19/2019 Ostwald and the Sistem of Color
48/50
Some conclusions
Ostwald managed to clear up the relationbetween the color circle and the spectrum
Ostwald managed to replace $eye measure% with colorimetric de&nitions
Ostwald!s color atlas may have a few 'aws, but
is a principled construction, in contradistinctionto Munsell!s mere eye measure result
Ostwald!s $spectroscopy % " when understood
rightly! # has many useful applications.
What ever happened to
8/19/2019 Ostwald and the Sistem of Color
49/50
What ever happened toOstwald!s Color Science?
History has not been kind to Ostwald . His major achievements arenot acknowledged in the Anglosaxon literature and ( whenmentioned at all ( are misinterpreted. An embarrassment!
For example, Ostwald!s color atlas is the only principled construction of its kind available today. It is di) erent in kind from the Munsell system in that it obviates the need for eyemeasure " psychology #. It is perfectly suited to the computer
age. Yet this remains unrecognized, despite the need.
The current industry standard " CIE*Lab # is an awkward mix ofcolorimetry and arbitrary de&nitions " loosely based on theMunsell system #, full of magical numbers and ad hoc functions.
Yet, commonly enough, people confuse it with science!
8/19/2019 Ostwald and the Sistem of Color
50/50
Thank you for your attention!
Top Related