Ruimte en Licht festival November 2016_Perceptie van ...
Transcript of Ruimte en Licht festival November 2016_Perceptie van ...
PERCEPTIE VAN DE HELDERHEID VAN LICHTBRONNEN
Peter Hanselaer
ESAT/Light&Lighting Laboratory, KU Leuven, BE
Ruimte en Licht FestivalEindhoven, 17 november 2016
New Light Sources
Lighting Optical design
AppearancePerception
MeasurementFacilities
Light&Lighting LaboratoryTopics
3
Introduction: colour and numbers
Stimulus
Light source
object , ( )eE λ λ
, ( )eL λ λ
4
ColorimetryBasic Elements
10
Reflectance Spectral radiance
2°
,
,
,
( ). ( )
( ). ( )
( ). ( )
e
e
e
X k L x
Y k L y
Z k L z
λ
λ
λ
λ λ
λ λ
λ λ
=
=
=
∑
∑
∑
5
ColorimetryTristimulus values
Colour Matching Functions
11
SpectralRadiance
From spectral radiance to tristimulus values (X,Y,Z)
6
ColorimetryColour coordinates
+( , )x y L ′ ′ +( , )u v L
11
From tristimulus values (X,Y,Z) to colour coordinates
7
ColorimetryColour coordinates
11
Disadvantages of colour coordinates
• Not uniform with respect to colour differences• Not directly related to perceptional quantities: hue,
saturation, brightness• Not considering background and surround
8
ColorimetryRelated stimuli
(X,Y,Z) or (x,y,L) is the typical colorimetric output for a single stimulusVisual perception is however strongly determined by the characteristics of stimulus and environment: related colours
12
9
ColorimetryColour Appearance Model
Colour appearance models CAM generate perceptualcorrelates of stimuli in relation to background and surround: brightness (lightness), hue, colourfulness (chroma, saturation)
CIECAM02 is an accepted CAM, mimicking some processesin the retina
14
ColorimetryCIECAM02
CIECAM02Model
SampleX,Y,Z
Correlates of:• redness/ greenness, a
• yellowness/ blueness, b
• brightness, Q• lightness, J• colourfulness, M• chroma, C• saturation, s• hue angle, h• hue composition, H
White
Xw,Yw,Zw
Surround
LA
Background
Avg, dim, dark
Chromaticadaptation
Cone response
Surroundinduction
10
Perception of light sourcesState-of-the-art
16
Dark background
5 years ago: three Colour Appearance Models
• CAM97u (Hunt, 1997)• ATD01(Guth, 2002)• CAMFu (Fu, 2012)• LEq (CIE, 2011)• LEq Nayatani (2 versions, 1997)
Low correspondence to our experimental data for the brightness of coloured stimuli due to an underestimation of
the Helmholtz-Kohlrausch effect
H-K: brightness perception increases with saturation
Perception of light sourcesState-of-the-art
17
Luminous background
No model available!
• Traffic signals• Display (smartphone, billboards)• Glare
Perception of light sourcesResearch questions
18
Part 1: can we improve the actualCAMs for a dark background?
Part 2: can we develop a new CAM for a luminous background?
Part 1: experimentalStimuli
• RGBW module, 10°FOV• 105 + 52 stimuli• 6 cd/m2 < L10 < 297 cd/m2
(photopic/glare)• Dark background• Chromaticity range:
19
Selection• 9 + 11 observers, aged 21 to 32• Laypersons
Q&A• Brightness compared to reference (temporal juxtaposition)• Amount of white versus colour in %• Relative amount of two unique hues• Magnitude estimation
Intra- and inter-observer variability• CV Hue: 10 to 11 %• CV Brightness: 14 to 20 %• CV Amount of white: 30 to 44%
Part 1: experimentalObservers
20
24
Part 1: experimentalHelmholtz-Kohlrausch
60 cd/m²60 cd/m²60 cd/m²60 cd/m² 218 cd/m²218 cd/m²218 cd/m²218 cd/m²
CAM97u
26
CAM15u: building the model Step 1: absolute cone excitations
830
10 e, 10
390
830
10 e, 10
390
830
10 e, 10
390
( ) ( )d
( ) m
666.7
782.3
1444
( )d
( ).6 s ( )d
λ
λ
λ
ρ λ λ λ
γ λ λ λ
β λ λ λ
=
=
=
∫
∫
∫
L l
L
L
• Absolute spectral radiance• CIE 2006 cone fundamentals (10°)• Normalization constants
27
• Power law• Power value: determined from observer
brightness data of neutral stimuli
10
1
1/3
1/30
1/0
1 3
ρ ργ γβ β
=
=
=
c
c
c
CAM15u: building the model Step 2: cone compression
28
CAM15u: building the model Step 3: neural signals
Achromatic signal
Red-green balance
Yellow-blue balance
c c c
1222
23.
0ρ γ β = + +
A
cc c
12( )
11 111
βρ γ= − +a
c c c( 2 )0.117 ρ γ β= + −b
29
CAM15u: building the model Step 4: hue, colourfulness, brightness, saturation, amount of white
1180Hue h tan ( / )
π−= b a
2 2Colourfulness 135.5 2= × +M a ba
b
h
0.561Brightness 2.559= + ×Q A M
Saturation = Ms
Q
2.68
100Amount of white
2.291=
+ ×W
s
30
New validation data set of 52 mixed chromatic andachromatic stimuli; magnitude estimation
Brightness Hue Amount of white
R² rS CV R² rS CV R² rS CVCAM15u 0.87 0.94 7 0.99 1.00 5 0.76 0.84 32CAM97u 0.36 0.57 16 0.99 0.99 5 - - -CAMFu 0.22 0.41 26 0.99 0.99 5 - - -
CAM15u: performance Hue, brightness, amount of white
31
CAM15u Application
European Standard for VMS (CEN, 2014) prescribes hue dependent maximum luminance values in dark viewing conditions (circles)
Perception of light sourcesResearch questions
33
Part 1: can we improve the actualCAMs for a dark background?
Part 2: can we develop a new CAM for a luminous background?
• 6 hues x 5 = 30 stimuli, 10° FOV• L10 = 50 cd/m2 (positive contrast)• Background: L10 = 28 cd/m2
CCT= 3880 K70° FOV
• 12 + 10 observers, aged 20 to 50• Graphical response sheet
Part 2: experimentalStimuli
34
35
Part 2: resultsH-K effect
Helmholtz-Kohlrausch is even important when a luminousbackground is present
36
Part 2: resultsBackground effect
Impact of the (neutral) background on the brightnessperception (red stimulus, 125 cd/m2)
Negativecontrast
37
Development of a new CAM for self-luminousstimuli and background
• First preliminary results (one fixed stimulus)• Helmholtz-Kohlrausch effect is still important• Positive and negative contrast: impact on
brightness• Modelling: in progress
Part 2Conclusions
Brightness 50 -> answer38
CAM15u References
Withouck, M., Smet, K., Ryckaert, W., Hanselaer, P. (2015). Experimental driven modelling of the color appearance of unrelated self-luminous stimuli: CAM15u. Optics Express, 23 (9), 12045-12064.
Withouck, M., Smet, K., Hanselaer, P. (2015). Brightness prediction of different sized unrelated self-luminous stimuli. Optics Express, 23 (10), 13455-13466.
Ready-to-use code available:
www.github.com/ksmet1977/CAM15u