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Sources, Surfaces, Eyes
An investigation into the interaction oflight sources, surfaces, eyes
IESNA Annual Conference, 2003
Jefferey F. KnoxDavid M. Keith, FIES
Sources, Surfaces, & Eyes - Research
* Research– Scientific activity dedicated to discovering
what makes grass green.• Russell Baker
Sources, Surfaces, and Eyes Overview
* Why is the spectral nature of light important?– Human color perception
* Why is a new calculation technique necessary?– The Lumen is spectrally ignorant
* What are the ramifications of a new calculation procedure?– more colorful predictions of our world
* For Instance…..
Spectral Information is Important
Spectral Information is Important
Spectral Information is Important
Spectral Information is Important
* Both Brightness and Color are needed to complete the human visual process
* In order to understand how including spectral information effects lighting, we need to understand the basics of radiation and light
Lighting Basics: The Lumen
Photopic Spectral Luminous Efficiency Function
0
0.2
0.4
0.6
0.8
1
1.2
360
394
428
462
496
530
564
598
632
666
700
734
768
802
WavelengthSe
nsiti
vity
Series1
Spectral Power Distribution 150 HPS
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+001.20E+00
1.40E+00
380
411
442
473
504
535
566
597
628
659
690
721
752
Wavelength (nm)
Pow
er (W
atts
)
Series1
Lumenssource = K * ∑ [ S(λ) * v(λ) ]Sum λ from 360 to 770 nanometers
Lumens = K * ∑ [ P(λ) * v(λ) ]
Lighting Basics: Reflectance
* Luminous reflectance:– Any of the geometric aspects of reflectance in
which both the incident and the reflected flux are weighted by the spectral luminous efficiency of radiant flux V(λ).
– Note: Unless otherwise qualified, the term “reflectance” means luminous reflectance.
– “GLOSSARY OF LIGHTING TERMINOLOGY” IESNA Lighting Handbook
Lighting Basics: Reflectance
* Reflectance = Lumensoff ÷ Lumenson
* Average Reflectance– What is average reflectance?– Is it related to a specific source?
Lighting Basics: Contrast
Cmod = (Lmax - Lmin ) / (Lmax + Lmin)
For a perfectly diffuse reflector Luminance = Exitance ÷ πExitance = Lumenson * Reflectance
Cmod = (p max - p min ) / (p max + p min)
Basic Problems: The Lumen
* The Lumen is Spectrally Ignorant– It contains no information about its spectral
composition.
Basic Problems: The Lumen
* A Lumen is a Lumen is a Lumen
Basic Problems: The Lumen
* A Lumen is a Lumen is a Lumen– Every lumen from a source is the same as every
other lumen from that source!
Basic Problems: The Lumen
* A Lumen is a Lumen is a Lumen– Every lumen from a sources is the same as every
other lumen from that source!– BUT!– Every lumen from one source is not the same as
every lumen from a different source.
Basic Problems: Reflectance
* Reflectance = Lumensoff ÷ Lumenson
* Because reflectance is lumen-based, it too is Spectrally Ignorant
* Every interaction of light with a surface changes the spectral distribution of every lumen reflected
Basic Problems: Reflectance
* Reflectance = Lumensoff ÷ Lumenson
* Because reflectance is lumen-based, it too is Spectrally Ignorant
* Every interaction of light with a surface changes the spectral distribution of every lumen reflected
* WHAT WE SEE IS REFLECTED LIGHT!
Basic Problems: Contrast
Can You See This?
Basic Problems: Contrast
Obviously we need to find some way to make better predictions that include color and color difference . . .
Why a New Calc. Technique
* Our world is not all shades of gray
Why a New Calc. Technique
* Our world is not all shades of gray* The effects of Color Difference need to be
evaluated and taken into consideration
New Calculation Basics
* Treat light as radiation – not as some compressed unit that follows energy theory
* Do not convert the radiation into lumens until it strikes the retina – and only if value information is all that is important
The New Basics - Reflectance
* Lumens onLumens on = K*∑[S(λ)*v(λ)]
* Lumens offLumens offclassic = ρaverage * {K*∑[S(λ)*v(λ)]}
Lumens offrevised = K * ∑ [ S(λ) * v(λ) * ρ (λ) ]
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
380 410 440 470 500 530 560 590 620 650 680 710 740 770
Ref
lect
ivity
0
50
100
150
200
250
380 410 440 470 500 530 560 590 620 650 680 710 740 770
wavelength (nm)
Spec
tral
Pow
er
Spectral Power Distribution Illum A
FHWA Blue Paint Spectral ReflectanceX
0
50
100
150
200
250
380 410 440 470 500 530 560 590 620 650 680 710 740 770
wavelength (nm)
Spec
tral
Pow
er
Product of Illum A & Blue Spectral Reflectance
=
0
50
100
150
200
250
380 410 440 470 500 530 560 590 620 650 680 710 740 770
wavelength (nm)
Spec
tral
Pow
er
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
380 410 440 470 500 530 560 590 620 650 680 710 740 770
wavelength (nm)
Rel
ativ
e M
agni
tude
Photopic Spectral Luminous Efficiency Function
Product of Illum A & Blue Spectral Reflectance
X
0
50
100
150
200
250
380 410 440 470 500 530 560 590 620 650 680 710 740 770
wavelength (nm)
Spec
tral
Pow
er=
Stimulus Produced by Illum A & Blue
683 * ∑ Stimulus = Lumens off
Spectral Reflectance Calculation
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
380 410 440 470 500 530 560 590 620 650 680 710 740 770
wavelength (nm)
Rel
ativ
e M
agni
tude
Source
Surface
Off Surface
vlambda
Stimulus
Sample Surface 5
00.20.40.60.8
11.2
380
409
438
467
496
525
554
583
612
641
670
699
728
757
Wavelength
Ref
lect
ivity
Series1
Sample Surface 4
00.20.40.60.8
11.2
380
409
438
467
496
525
554
583
612
641
670
699
728
757
Wavelength
Ref
lect
ivity
Series1
Sample Surface 3
00.20.40.60.8
11.2
380
409
438
467
496
525
554
583
612
641
670
699
728
757
Wavelength
Ref
lect
ivity
Series1
Sample Surface 2
00.20.40.60.8
11.2
380
409
438
467
496
525
554
583
612
641
670
699
728
757
Wavelength
Ref
lect
ivity
Series1
Sample Surface 1
00.20.40.60.8
11.2
380
409
438
467
496
525
554
583
612
641
670
699
728
757
Wavelength
Ref
lect
ivity
Series1
Sample Surface 0
0
0.05
0.1
0.15
0.2
0.2538
0
409
438
467
496
525
554
583
612
641
670
699
728
757
Wavelength
Ref
lect
ivity
Series1
What does all this mean?Reflectance of sample surfaces under different sources
Samp0 Samp1 Samp2 Samp3 Samp4 Samp5
wrt D65
x 0.31 0.13 0.21 0.37 0.53 0.68
y 0.33 0.15 0.77 0.63 0.47 0.32
EqEnergy 20% 20% 20% 20% 20% 20%
D65 20% 22% 21% 20% 19% 18%
Illum A 20% 12% 17% 20% 23% 28%
HPS 20% 3% 2% 21% 45% 27%
M25H 20% 14% 19% 19% 34% 13%
M25U 20% 11% 21% 17% 40% 10%
M40H 20% 15% 19% 20% 32% 13%
M40U 20% 12% 19% 17% 38% 13%
What does all this mean?Reflectance of sample surfaces under different sources
Samp0 Samp1 Samp2 Samp3 Samp4 Samp5
wrt D65
x 0.31 0.13 0.21 0.37 0.53 0.68
y 0.33 0.15 0.77 0.63 0.47 0.32
EqEnergy 20% 20% 20% 20% 20% 20%
D65 20% 22% 21% 20% 19% 18%
Illum A 20% 12% 17% 20% 23% 28%
HPS 20% 3% 2% 21% 45% 27%
M25H 20% 14% 19% 19% 34% 13%
M25U 20% 11% 21% 17% 40% 10%
M40H 20% 15% 19% 20% 32% 13%
M40U 20% 12% 19% 17% 38% 13%
What does all this mean?Reflectance of sample colors under different sources
Samp0 Samp1 Samp2 Samp3 Samp4 Samp5
wrt D65
x 0.31 0.13 0.21 0.37 0.53 0.68
y 0.33 0.15 0.77 0.63 0.47 0.32
EqEnergy 20% 20% 20% 20% 20% 20%
D65 20% 22% 21% 20% 19% 18%
Illum A 20% 12% 17% 20% 23% 28%
HPS 20% 3% 2% 21% 45% 27%
M25H 20% 14% 19% 19% 34% 13%
M25U 20% 11% 21% 17% 40% 10%
M40H 20% 15% 19% 20% 32% 13%
M40U 20% 12% 19% 17% 38% 13%
What does all this mean?Reflectance of sample surfaces under different sources
Samp0 Samp1 Samp2 Samp3 Samp4 Samp5
wrt D65
x 0.31 0.13 0.21 0.37 0.53 0.68
y 0.33 0.15 0.77 0.63 0.47 0.32
EqEnergy 20% 20% 20% 20% 20% 20%
D65 20% 22% 21% 20% 19% 18%
Illum A 20% 12% 17% 20% 23% 28%
HPS 20% 3% 2% 21% 45% 27%
M25H 20% 14% 19% 19% 34% 13%
M25U 20% 11% 21% 17% 40% 10%
M40H 20% 15% 19% 20% 32% 13%
M40U 20% 12% 19% 17% 38% 13%
Sample Color ReflectancesSample Surfaces' Reflectances
0%5%
10%15%20%25%30%35%40%45%50%
Samp0 Samp1 Samp2 Samp3 Samp4 Samp5
EqEnergyD65Illum AHPSM25HM25UM40HM40U
Sign ColorsOrange 0.553 0.383 0.064 33.0%
Daytime33% 10564.75 5033.85 3481.15 584.59 X Y
0.562 0.35Refl D65*vl rho*X*S rho*Y*S rho*Z*S Wave S*rho 0.645 0.355
0.57 0.4290.100 1.95E-03 0.01 0.00 0.03 380 5.0 0.506 0.4040.100 3.35E-03 0.01 0.00 0.05 385 5.2 0.553 0.3830.100 6.56E-03 0.02 0.00 0.11 390 5.50.100 1.49E-02 0.05 0.00 0.25 395 6.90.100 3.28E-02 0.12 0.00 0.56 400 8.30.100 5.58E-02 0.20 0.01 0.96 405 8.70.050 1.11E-01 0.20 0.01 0.95 410 4.60.050 2.02E-01 0.36 0.01 1.72 415 4.60.050 3.74E-01 0.63 0.02 3.02 420 4.70.050 6.57E-01 0.97 0.03 4.68 425 4.50.050 1.01E+00 1.23 0.05 6.01 430 4.30.050 1.61E+00 1.57 0.08 7.77 435 4.80.050 2.41E+00 1.83 0.12 9.16 440 5.20.050 3.30E+00 1.93 0.17 9.88 445 5.50.050 4.45E+00 1.97 0.22 10.37 450 5.90.050 5.64E+00 1.87 0.28 10.24 455 5.90.050 7.07E+00 1.71 0.35 9.83 460 5.90.050 8.59E+00 1.46 0.43 8.89 465 5.80.050 1.04E+01 1.12 0.52 7.37 470 5.70.050 1.30E+01 0.82 0.65 6.01 475 5.80.050 1.61E+01 0.55 0.81 4.71 480 5.80.050 1.90E+01 0.33 0.95 3.46 485 5.6
0
10
20
30
40
50
60
70
80
380 420 460 500 540 580 620 660 700 740 780
0.3
0.32
0.34
0.36
0.38
0.4
0.42
0.44
0.2 0.3 0.4 0.5 0.6 0.7
Color Reproduction
Sign Colors
New Reflectance DataReflectances of FHWA Sign and Pavement Paints Under
Different Sources of IlluminationBlack Blue Green Yellow Orange Red White PMWhite PMYellow
x 0.31 0.14 0.13 0.49 0.55 0.61 0.31 0.31 0.44y 0.33 0.14 0.49 0.48 0.38 0.31 0.33 0.33 0.43
EqEn 2% 19% 31% 75% 35% 16% 90% 75% 68%D65 2% 21% 33% 73% 33% 14% 90% 75% 66%Illum A 2% 12% 23% 83% 44% 22% 90% 75% 74%HPS 2% 4% 6% 95% 58% 20% 90% 74% 87%M25H 2% 13% 24% 82% 39% 14% 90% 75% 74%M25U 2% 11% 22% 84% 39% 13% 90% 76% 76%M40H 2% 15% 26% 80% 38% 13% 90% 75% 73%M40U 2% 12% 22% 84% 41% 14% 90% 76% 76%
New Reflectance DataReflectances of FHWA Sign and Pavement Paints Under
Different Sources of IlluminationBlack Blue Green Yellow Orange Red White PMWhite PMYellow
x 0.31 0.14 0.13 0.49 0.55 0.61 0.31 0.31 0.44y 0.33 0.14 0.49 0.48 0.38 0.31 0.33 0.33 0.43
EqEn 2% 19% 31% 75% 35% 16% 90% 75% 68%D65 2% 21% 33% 73% 33% 14% 90% 75% 66%Illum A 2% 12% 23% 83% 44% 22% 90% 75% 74%HPS 2% 4% 6% 95% 58% 20% 90% 74% 87%M25H 2% 13% 24% 82% 39% 14% 90% 75% 74%M25U 2% 11% 22% 84% 39% 13% 90% 76% 76%M40H 2% 15% 26% 80% 38% 13% 90% 75% 73%M40U 2% 12% 22% 84% 41% 14% 90% 76% 76%
New Reflectance DataReflectances of FHWA Sign and Pavement Paints Under
Different Sources of IlluminationBlack Blue Green Yellow Orange Red White PMWhite PMYellow
x 0.31 0.14 0.13 0.49 0.55 0.61 0.31 0.31 0.44y 0.33 0.14 0.49 0.48 0.38 0.31 0.33 0.33 0.43
EqEn 2% 19% 31% 75% 35% 16% 90% 75% 68%D65 2% 21% 33% 73% 33% 14% 90% 75% 66%Illum A 2% 12% 23% 83% 44% 22% 90% 75% 74%HPS 2% 4% 6% 95% 58% 20% 90% 74% 87%M25H 2% 13% 24% 82% 39% 14% 90% 75% 74%M25U 2% 11% 22% 84% 39% 13% 90% 76% 76%M40H 2% 15% 26% 80% 38% 13% 90% 75% 73%M40U 2% 12% 22% 84% 41% 14% 90% 76% 76%
New Reflectance DataReflectances of Asphalt and Concrete Under Seven
Different Sources of Illumination
As1 As2 As3 Co1 Co2 Co3 Co4 Co5x 0.35 0.34 0.32 0.33 0.33 0.35 0.35 0.35y 0.36 0.36 0.34 0.35 0.35 0.35 0.36 0.36
EqEn 7.4% 7.3% 7.6% 33.3% 33.3% 26.0% 18.2% 25.9%D65 7.3% 7.3% 7.6% 33.2% 33.2% 25.7% 18.1% 25.7%Illum A 7.6% 7.5% 7.6% 33.7% 33.6% 26.8% 18.8% 26.6%HPS 7.7% 7.6% 7.7% 34.1% 34.0% 28.0% 19.4% 27.7%M25H 7.4% 7.4% 7.6% 33.5% 33.5% 26.4% 18.5% 26.3%M25U 7.5% 7.4% 7.6% 33.6% 33.6% 26.5% 18.6% 26.5%M40H 7.4% 7.3% 7.6% 33.5% 33.4% 26.3% 18.4% 26.2%M40U 7.5% 7.4% 7.6% 33.6% 33.6% 26.6% 18.6% 26.5%
New Basics - Contrast
* Same standard equation
Cmod = (p max - p min ) / (p max + p min)
– Still calculated in lumens
* Different method for calculating reflectance
New Basics – Color Difference
* Threshold– The difference in chromaticity or luminance
between two colors that makes them just perceptibly different. The difference may be in hue, saturation, brightness(lightness for surface colors) or a combination of the three.
New Basics – CIE L*a*b*
* First, the illuminant in the local context can be specified, also in terms of the R, G and B cone outputs, as a reference white. That is, the model
treats all colors as a combination of surface color and illuminant color, which allows the model to
be applied across a wider range of viewing conditions.
New Basics – CIE L*a*b*
* Second, the trichromatic XYZ "primaries" are transformed mathematically to represent the Y/B
and R/G opponent dimensions (along with a lightness or white/black dimension), which allows
the models to reproduce the basic structure of color experience.
New Basics – CIE L*a*b*
* Finally, CIELAB is based on a set of imaginary “primary” lights that have been chosen
specifically to make the color space perceptually uniform (at least, to the degree possible in a three
dimensional model). That is, a difference of 10 units on the lightness dimension has the same
perceptual impact as a 10 unit difference on the Y/B or R/G dimensions -- either separately or in
combination.
New Basics – CIE L*a*b*
* delLAB is the Euclidean distance between two color loci
* ΔLAB = {(ΔL)2 + (Δa)2 + (Δb)2}1/2
Sign Colors – Contrast & delLAB
White on Red Black on White Black on Orange Black on Yellow White on GreenContrast delLAB Contrast delLAB Contrast delLAB Contrast delLAB Contrast delLAB
EqEnergy 0.70 95 0.96 81 0.89 98 0.95 135 0.49 126
CIE D65 0.72 96 0.96 81 0.89 96 0.95 133 0.46 125
CIE A 0.60 101 0.96 81 0.91 108 0.95 138 0.59 121
HPS 0.63 76 0.96 81 0.93 112 0.96 148 0.87 100
M25H 0.74 82 0.96 81 0.90 99 0.95 138 0.58 114
M25U 0.75 77 0.96 81 0.90 97 0.95 141 0.61 107
M40H 0.74 84 0.96 81 0.90 98 0.95 137 0.56 116
M40U 0.73 79 0.96 81 0.91 99 0.95 140 0.61 110
Sign Colors – Contrast & delLAB
White on Red Black on White Black on Orange Black on Yellow White on GreenContrast delLAB Contrast delLAB Contrast delLAB Contrast delLAB Contrast delLAB
EqEnergy 0.70 95 0.96 81 0.89 98 0.95 135 0.49 126
CIE D65 0.72 96 0.96 81 0.89 96 0.95 133 0.46 125
CIE A 0.60 101 0.96 81 0.91 108 0.95 138 0.59 121
HPS 0.63 76 0.96 81 0.93 112 0.96 148 0.87 100
M25H 0.74 82 0.96 81 0.90 99 0.95 138 0.58 114
M25U 0.75 77 0.96 81 0.90 97 0.95 141 0.61 107
M40H 0.74 84 0.96 81 0.90 98 0.95 137 0.56 116
M40U 0.73 79 0.96 81 0.91 99 0.95 140 0.61 110
Sign Colors – Red & White
Sign Colors – Black & Orange
Sign Colors – Black & Yellow
Asphalt & Paint – Contrasts and del L*a*b*PmWhite on As1 PmWhite on As2 PmWhite on As3Contrast delLAB Contrast delLAB Contrast delLAB
CIE D65 0.82 58 0.82 58 0.82 57CIE A 0.82 58 0.82 57 0.81 56EqEnergy 0.82 58 0.82 58 0.82 57HPS 0.81 57 0.81 57 0.81 56M25H 0.82 58 0.82 58 0.82 56M25U 0.82 58 0.82 58 0.82 56M40H 0.82 58 0.82 58 0.82 56M40U 0.82 58 0.82 58 0.82 57
PmYellow on As1 PmYellow on As2 PmYellow on As3Contrast delLAB Contrast delLAB Contrast delLAB
CIE D65 0.80 75 0.80 76 0.79 79CIE A 0.81 81 0.82 82 0.81 86EqEnergy 0.80 76 0.81 77 0.80 81HPS 0.84 90 0.84 91 0.84 96M25H 0.82 81 0.82 82 0.81 87M25U 0.82 82 0.82 83 0.82 88M40H 0.82 80 0.82 82 0.81 86M40U 0.82 82 0.82 84 0.82 88
Concrete & Paint – Contrasts & del L*a*b*PmWhite on Co1 PmWhite on Co2 PmWhite on Co3 PmWhite on Co4 PmWhite on Co5
Contrast delLAB Contrast delLAB Contrast delLAB Contrast delLAB Contrast delLABCIE D65 0.39 26 0.39 26 0.49 34 0.61 42 0.49 35CIE A 0.38 26 0.38 26 0.47 30 0.60 36 0.47 30EqEn 0.39 26 0.39 26 0.49 30 0.61 36 0.49 30HPS 0.37 25 0.37 25 0.45 28 0.59 35 0.46 29M25H 0.38 27 0.39 27 0.48 30 0.61 36 0.48 30M25U 0.38 26 0.38 26 0.48 30 0.61 36 0.48 30M40H 0.39 27 0.39 27 0.48 30 0.61 36 0.48 30M40U 0.38 26 0.38 26 0.48 30 0.60 36 0.48 30
PmYellow on Co1 PmYellow on Co2 PmYellow on Co3 PmYellow on Co4 PmYellow on Co5
Contrast delLAB Contrast delLAB Contrast delLAB Contrast delLAB Contrast delLABCIE D65 0.33 59 0.33 59 0.44 58 0.57 62 0.44 57CIE A 0.38 66 0.38 67 0.47 64 0.60 68 0.47 62EqEn 0.34 60 0.34 61 0.45 59 0.58 63 0.45 58HPS 0.44 75 0.44 75 0.51 72 0.63 77 0.52 70M25H 0.38 65 0.38 65 0.47 63 0.60 68 0.48 63M25U 0.39 66 0.39 66 0.48 65 0.61 69 0.48 63M40H 0.37 64 0.37 64 0.47 63 0.60 67 0.47 62M40U 0.39 66 0.39 66 0.48 65 0.61 69 0.48 64
Summary
* Keep the spectral information in the calc.* Spectral effects of illuminants cannot be
evaluated without considering the spectral reflectance of the lighted surfaces
* All this is evaluated as single bounce applications (no inter-reflections!)
* The significance of spectral effects can be greater when inter-reflections occur
Sources, Surfaces, Eyes
An investigation into the interaction oflight sources, surfaces, eyes.
IESNA Annual Conference, 2003
Jefferey F. KnoxDavid M. Keith, FIES
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