I.
Color Perception
II. Color Principles
III. Color Space
IV. Color Measurement
V. Database Guide
I. Color Perception
Light source Observer
Object
I. Color Perception
1. Light Source
Why we need it?
Standard
Lighting
Cool White Fluorescent Incandescent A
VISIBLE SPECTRUM
Visible Light
1pm 1A 1nm 1mm 1m 100m
Short waves
UV
X-Ray Ultrashort
waves
Gamma Infrared
Wave Length (nm)
Black body
Light source
Spectral Power Distribution (SPD)
In Spectrophotometer
Detector
I. Color Perception
2. Observer
Observer
The eye
The CIE Standard
Observer
The experimentally
derived x, y, and z
functions became the
CIE 1931 2º Standard
Observer.
These functions quantify
the red, green and blue
cone sensitivity of the
average human observer.
Of the two observers, the
CIE recommends the 10º
Standard Observer.
It best correlates with
average visual assessments
made with large fields of
view, typical of most
commercial applications.
I. Color Perception
3. Object
Object
Reflectance Blue
Absorb Yellow
and Red
Primary Types of Light Distribution
When light strikes on an object, one or more of the 4 primary types of
light distribution occur:
Light source 2, 10 Observer
STD.
Illuminant STD
Object
% Reflectance
II. Color Principles
II. Color Principles
1. Additive Color Matching
II. Color Principles
2. Subtractive Color Matching
The working principle of the CMYK
system is to absorb light. The
color can see is a part of the light
that is not absorbed
III. Color Space
CIE : COMMISSION INTERNATIONALE DE L'ECLAIRAGE
or INTERNATIONAL COMMIISSION ON ILLUMINATION
III. Color Space
Show color in 3 dimension
L* = Lightness
a* = Green (-a*) , Red (+a*)
b* = Blue (-b*), Yellow (+b*)
Color Difference
+L
CIELab Color Difference
+DL
Trial Standard
Lighter
- = Redder +Da,-Db
Less Yellow
-L
L* = 40.40 L* = 39.90 DL* = 0.50
a* = 49.49 a* = 48.04 Da* = 1.45
b* = 13.83 b* = 17.18 Db* = -3.35
dE*= (dL*2 + da*2 + db*2) ½ = 5.3
Fundamentals of Color and Appearance © GretagMacbeth
III. Color Space
IV. Color Measurement
1. Strength Caculations
Color strength is defined as a pigments ability to
change the color of a otherwise color less
material.
This is a numerical value related to the amount of light-
absorbing material (colorant) contained in a sample.
SWL SUM WSUM
% (Color) Strength SWL
Single Wavelength Lowest reflectance
If standard and sample have different
wavelengths of maximum of absorption this
method will not deliver correct results.
K is the light absorption coefficient
S is the light scattering coefficient
R is the percentage reflectance at the wavelength of maximum
absorption
% (Color) Strength SUM
The % strength SUM represents the ratio of
(K/S) data between sample and standard at all
visual wavelength (400-700nm)
The selection of different illuminant observer
condition has no influence on the result.
K is the light absorption coefficient
S is the light scattering coefficient
R is the percentage reflectance at each wavelength across
the spectrum
% (color) Strength WSUM
The strength WSUM represents the ration of sums
of (K/S) data multiplied by the sum of weighted
observer/illumination at all wavelengths for the
sample in relation to the standard.
The result is illuminant/observer depending.
K is the light absorption coefficient
S is the light scattering coefficient
R is the reflectance at each wavelength across the spectrum
IV. Color Measurement
2. Gloss Effect on Color Difference Measurement
The diffuse reflection of light refers to when
light is scattered in various directions.
This reflection of light occurs more strongly on
rough, textured, and irregular surface
conditions, making an object appear less
saturated and duller in color.
With specular reflection, light reflects in the
same way – at an equal, but opposite.
This reflection of light occurs more strongly on
glossy surfaces, making an object appear
more saturated and vivid in color.
• High gloss surfaces cause a strong specular reflection of light and weak
diffuse reflection of light, resulting in a more saturated, vivid color
• Semi-gloss surfaces cause the specular reflection of light to mix with the
diffuse reflection of light, resulting in a less saturated, lighter color
• Matte surfaces cause a strong diffuse reflection of light and weak
specular reflection of light, resulting in a less saturated, duller color
Color Measurement: Specular Component Included or
Specular Component Excluded?
Specular Component Included Specular Component Excluded
This type of measurement includes
This type of measurement excludes
both specular and diffused reflected
any specular reflected light, making it
light, making it unaffected by any
more sensitive to surface conditions
surface conditions
The glossy object would fall in a
darker, more saturated region of the
Different surface not effect to true defined color space and the rough-
color surfaced object would fall in a lighter,
less saturated region of the defined
color space.
This mode is ideal when formulating This mode is more often used during
recipes to match colors and meet quality control evaluations to ensure
color quality standards more the appearance of their products
effectively. maintain consistency and meet the
standard
IV. Color Measurement
3. What is Metamerism?
“Metamerism is the phenomenon wherein two color samples
will appear to be of the same shade under one light source
but will appear to be different shades under a second source”
D65 CWF A
Standard
Standard
Standard
Sample
Sample
Sample
CW-F OH! It looks Bad !!
D65
Detecting Metamerism
Always use least 2 illuminants
Such as D65 and A for detection of
metamerism.
V. Database Guide
The ideal mixtures of colorant with white, black and resin depend on the
individual condition in a given system.
When weighting water put 1 cc. will get 1 g., 2 cc. get 2 g. , 3 cc. get 3 g. this is basic
synthesis logic , but in actual 1 cc. get 1.01 g. (diff. 0.01), 2 cc. get 1.98 g, (diff. 0.02)
Back to dBase color it more detail for create synthesis logic example 400-700 nm. And
reflectance it can compare synthesis curve and actual curve then show in dE*
When calculate the software check both side over light (over white) and Over dark (over
black) this function for software leaning light reflectance then can calculate opacity value.
THANKS FOR YOUR
ATTENTION !
