Color and Appearance Attributes

Richard W. HaroldColor and Appearance Consulting LLC

NOTE: This presentation was originally presented in the year 2000 at the NIST Color Workshop as a Keynote Speaker

Presentation. It is only 7.2 MB in Length. Additional, vastly improved Recent Presentations are available, but all far exceed 10

MB in Length

APPEARANCE: A Visual Sensation

CHROMATIC ATTRIBUTESRelated to color-hue, saturation, purity

GEOMETRIC ATTRIBUTESSurface properties associated with

the distribution of light from the object, such as gloss or haze

Opaque Non-MetalINCIDENT

LIGHT

SPECULARREFLECTION

DIFFUSEREFLECTION

MetalINCIDENT

LIGHTSPECULAR

REFLECTION

DIFFUSEREFLECTION

Translucent MaterialINCIDENT

LIGHT

SPECULARREFLECTION

DIFFUSEREFLECTION

DIFFUSETRANSMISSION

Transparent MaterialINCIDENT

LIGHT

SPECULARREFLECTION

DIFFUSETRANSMISSION

REGULARTRANSMISSION

Visual Observing Situation

OBJECT

LIGHT SOURCE

HUMAN OBSERVER

300 nm 450 550 650 1000 nm

VISIBLE SPECTRUM INFRAREDULTRAVIOLET

Spectral Power Distribution

UVX-

RAYSGAMMA

RAYSCOSMIC

RAYSINFRA-

REDMICRO-WAVES

TV RADIOELECTRIC

POWER

.00001nm .001nm 1nm 10nm .01cm .1 m 10 m 100m 106m

DaylightRelativeEnergy

Light Sources CIE Illuminants

Common Illuminants

CIE X,Y,Z Tristimulus Values for Orange

X = 41.73Y = 33.77Z = 2.34

Non-Uniformity of CIE Color Space

x

y

OPPONENT COLORS THEORY

BRAIN

BLUE RECEPTORS

GREEN

RECEPTORS

RED RECEPTORS

BLUE-YELLOW SIGNAL

BLACK-WHITE

SIGNAL

RED-GREEN SIGNAL

+60

-20

+20-40-60

-60-40

-20

0

+20

+60

+40

BLUE

RED

GREEN

YELLOW

WHITE

BLACK

LIGHTNESS

L = 58.12a = + 30.41b = + 36.26

100

+40

Comparison of Color Formulas

Hunter L, a, b (1958) CIE 1976 L* a* b*

CIE 1976 L* C* h

Hunter L, a, b (1958) CIE 1976 L*a*b*

Comparison of Hunter L, a, b to CIELAB

L* = 64.79a* = +32.21b* = +83.43

L = 58.12a = +30.41b = +36.26

Rectangular L* a* b* Color DifferencesSAMPLE STANDARD

COLORDIFFERENCE

S

L* = 75.7a* = +4.1b* = +87.6

L* = 71.6a* = +6.9b* = +78.7

Total Color Difference in Rectangular Coordinates

Sample Color

Standard Color

Sample Color

Standard Color

Interpretation of Color Differences

Instrumental Limit

10

1.0

2.0

5.0

0.5

0.2

0.01

TypicalIndustrialTolerance

Range

ApproximateVisual Limit

CIELAB UNITS

TYPICAL RECTANGULAR-COORDINATE TOLERANCES

Clothing Manufacturer

COLOR

Reds/Oranges

Greens

Yellows/Tans

Blues

Problem of Rectangular ± ∆ L* a* b* Tolerances

±∆ b*

±∆ a*

Product Standard

Acceptable Match

Visually Unacceptable Match

Yellow

+b*

Blue-b*

Red+a*

Green-a*

L* White

L* Black

C*ab

hab

L* = 64.79a* = 32.21b* = 83.43

L* = 64.78C*ab = 89.43hab = 68.89º

Tolerance Improvementwith ± ∆L* ± ∆C* ± ∆H* Coordinates

± ∆ L*

± ∆ C*

± ∆ H*

Product Standard

Acceptable Match

∆ECMC Total Color Difference

l:c = lightness to chroma ratio

Product Standard

HS

CcS

lSL

∆E*94 Total Color Difference

SL = 1SC = 1 + 0.045 C*ab

SH = 1 + 0.015 C*ab

kL = kC = kH = 1 under reference conditions

HS

CS

SL

Product Standard

∆E*2000? Total Color Difference

SL = 1

SH = 1 + 0.015 C*Tf

RT=HSCS

SL

Product Standard

45°/ 0°

ASTM D1729 Standard Practice for Visual Evaluation

• LIGHT SOURCESo Daylight (D50 ,D65 or D75) - Specifyo Incandescent - 2856Ko Cool White Fluorescent - 4200K

• PHOTOMETRIC CONDITIONS o Illumination of 810-1880 Lux

• GEOMETRIC CONDITIONSo Lighting overhead (0°)o Viewing (45°)

• BACKGROUND and SURROUNDo Neutral Greyo Uncluttered

Visually Evaluating Appearance

GLOSSCOLOR

60° 60°

85°85°20°20°

ASTM D523 Glossmeter Geometries

Variations in Paint Finish – “Orange Peal”

DISTINCTNESS

OF IMAGESPECULAR

HAZE

DIFFUSE30° 30°

DOI Abridged Goniophotometer

0°/45° 45°/ 0°

CIE Reciprocal Geometries

1928 Hardy Recording Photoelectric Color Analyzer

High Gloss

Matte

Textured

HIGH-GLOSS

Light Distribution Varies with Surface Smoothness

MATTE

SEMI-GLOSS

Goniophotometric Data for 45º Incident Light

Comparison of Glossy Red Plastic Other Textures

Goniophotometric Data for 45º Incident Light

Comparison of Different Textures of Red Plastic

Goniophotometric Data for 45º Incident Light

Comparison of Different Textures of Red Plastic

Integrating Sphere

White or BlackSpecular Port

Cover

Detector

Baffle

Lamp

CIE d/0 Geometry

CIE 45/0 Geometry

The Ideal Sample for Color Measurement

• Totally Opaque or Transparent• Flat• Smooth• Uniform• No-directionality• Not-photochromic• Not-thermochromic• Not-hygrochromic

FluorescenceDaylight

Illumination

Ultra Violet Illumination

ChromaFlair® Interference Pigments

Top half 45º/0º – Bottom half 0º/10º

ASTM Illuminating/Viewing Angle Nomenclature

Illumination angle=45º, Viewing Angle=65º, Aspecular Angle=45+65=110º

Dynamic Color AreaPearlescent/Interference

Samples

100 a*

b*

Sources of Measurement Differences

• Instrumental – sphere (d/8°) or 0°/45° or ?• Specimen Preparation• Specimen Presentation

BCRA Standards Set

Small Area View BCRA Tile Holder

Use And Care of Instrument Standards

• Permanent reference base against which instrumental measurements are made

• Accuracy and precision of appearance measurements depend upon initial calibration and condition of the standards

• Should be handled with care, cleaned according to instructions, and stored in the box provided