Colour vision
János Schanda Virtual Environments and Imaging
Technologies LaboratoryUniversity of Pannonia
Overview Human trichromacy
The human retina Colour deficiencies
Path from the retina to the cortex Brightness versus luminance
The fifth light sensitive cell in the human retina
Visibility
Perceiving details Rapid identification Brightness/lightness
evaluation Hue & colourfulness
evaluation
The eye
The structure of the eye
The human eyeFovea: only cones, covered by the macula lutea, yellow pigmentation.Foveola: central parto of fovea, only L and M cones, blue colour blind.
Artist’s view of the structure of the foveal
retina
Light perception Imaging the exterior
world on the retina The retina and its
most sensitive part the fovea
The receptive cells
The structure of the retina
Cones and rods
Distribution of rods and cones within the retina
Spectral sensitivity of the three cone types, logarithmic scale
-8
-7
-6
-5
-4
-3
-2
-1
0
1
350 450 550 650 750
wavelength, nm
log
cone
act
ion
sens
itivi
ty
L-cone
M-cone
S-cone
Fundamental colour matching experiment
Wright and Guild experiments
Different fundamentals
Transformed to common basis
R, G, B primary based CMFs
R: 1 unit, 700 nm
G: 4,5907 units, 546,1 nm
B: 0,0601 units, 435,8 nm
Background information CIE 1931 2° standard colorimetric
observer and Colour Matching Functions (CMFs) CIE 1924 spectral luminous efficiency
function CIE 1964 10° standard colorimetric
observer and CMFs
CIE TC 1-36 report Fundamental Chromaticity Diagram
with Physiological Axes - Part 1: CIE 170:2006 L,M,S cone fundamentals Photopigment absorption spectrum
Macular pigment absorption Field size dependence
Sties-Burch colour matching functions
wavelength (nm)
tristimulus values
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
350 400 450 500 550 600 650 700 750 800 850
_
_
l
r (λ )
_g (λ )b (λ )
Macular pigment optical density
wavelength (nm)
Opt
ical
Den
sity
0.0
0.1
0.2
0.3
0.4
350 400 450 500 550 600
2o
10 o
Lens and ocular media optical density
wavelength (nm)
Opt
ical
Den
sity
0.0
0.5
1.0
1.5
2.0
2.5
350 400 450 500 550 600 650 700
Derived photopigment low density absorbance
wavelength (nm)
Opt
ical
Den
sity
0.0
0.5
1.0
1.5
2.0
2.5
350 400 450 500 550 600 650 700
Complete path of getting to the corneal level cone
fundamentals
Photopigment low density
spectral absorbance
Ai,o(L-pigment)()Ai,o(M-pig ment)()Ai,o(S-pigment)()
Cornea
Retina
2° cone fundamentals
l2(), m2(), s2()
Macularpigment o.d.
2 deg
Lenspigment
o.d.
Cone photopigment o.d.
2 deg
FittedCMFs
2 deg
10° cone fundamentals
l10(), m10(), s10()
Cone photopigment o.d. 10 deg
ReferenceCMFs
10 deg
Lenspigment
o.d.
Macularpigment o.d. 10 deg
Stiles & Burch
Photopigment low density
spectral absorbance
Ai,o(L-pigment)()Ai,o(M-pig ment)()Ai,o(S-pigment)()
Cornea
Retina
2° cone fundamentals
l2(), m2(), s2()
Macularpigment o.d.
2 deg
Lenspigment
o.d.
Cone photopigment o.d.
2 deg
FittedCMFs
2 deg
10° cone fundamentals
l10(), m10(), s10()
Cone photopigment o.d. 10 deg
ReferenceCMFs
10 deg
Lenspigment
o.d.
Macularpigment o.d. 10 deg
Stiles & Burch
2° cone fundamentals
Spectral sensitivity of the three cone types, linear scale
Transformation to XYZ-like CMFs for the 2°observer(tentative equation!)
CIE 2° and cone fundamental derived (CFD) 2° CMFs
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
350 400 450 500 550 600 650 700 750 800
wavelength, nm
tris
itm.v
alue
s
x¯(λ)y¯(λ)z¯(λ)xF¯(λ)yF¯(λ)zF¯(λ)
Standard and cone
fundamental
chromaticity diagram
(Insert: DE per wavelength)
D(u’,v’) differences if the CIE 2° observer is used or the tentative CMFs of CIE TC 1-36
Calculated chromaticities usingCIE 1931 2° CMFs
0,3
0,4
0,5
0,6
0,0 0,1 0,2 0,3 0,4 0,5 0,6
u'
v'
RGB LEDVisual averageBroad-band reference
#1
#2
#3
#4#5
#7
#8#9#6
CIE 1931 2° CFD-CMF
1 0,025 0,0112 0,038 0,0133 0,025 0,0104 0,013 0,0055 0,003 0,0026 0,002 0,0037 0,017 0,0098 0,002 0,0039 0,006 0,004
Dom. wavelength: 626 nm, 525 nm, 473 nm
CIE u’,v’ differences in case of CIE 2°, TC1-36 2° (Fundamental CMFs) und modified
2° Őbserver (Mod.Fund. CMFs)
0,000
0,005
0,010
0,015
0,020
0,025
0,030
0,035
0,040
0,045
0,050
Sample #1
Sample #2
Sample #3
Sample #4
Sample #5
Sample #6
Sample #7
Sample #8
Sample #9
Chromaticity differences using different CMFs (CIE 1976 u'v')
CIE 1931 2° CMFsFundamental CMFsModified Fundamental CMFs
Retinal processing Cone vision -> foveal
vision Long wave -L- Medium wave -M- Short wave -S-
sensitive cones
New signals are created already at retinal level Receptor cells produce
analogue potential difference for excitation
At output (ganglion cell) level fireing frequency signal is produced
Antagonistic colour channels and the brightness/lightiness channel
ON and OFF signals The ON centre
bipolar cell is activated by the cone signal
The OFF centre cell gets activated as the light decreases.
Differences in the ganglion cell fireing rate
Receptive fields, functional diagram
Receptive fields
Neural signal generation H1 &H2: horizontal cells,
participate in the antagonistic signal processing
B: bipolar cells, participate in the centre/surrounding antagonistic process (ON and OFF cells)
G: ganglion cells MC: magnocellular (ON and
OFF cells) PC: parvocellular (2 ON and
OFF cells) KC: koniocellular (2 ON cells)
Neural pathway - 1 Achromatic channel:
L + M cone signal Sensitive on edges, contrast Luminance like spectral responsivity
flicker photometry small step brightness comparison
Rapid signal transmission Neurons leading to magnocellular layers
Standardised visibility functions
0
0.2
0.4
0.6
0.8
1
1.2
350 400 450 500 550 600 650 700 750 800
wavelength, nm
rel.
sens
itivi
ty
V(l)VM(l)V´(l)y(l)10
Neural pathways -2
Parvocellular: L-M cone signal Fine details, slow Red – green antagonistic structure
Koniocellular: S – L, M-S cone signals Slow Yellow – blue antagonistic structure
Way of the colour signal from the retina to the
brain
Lateral geniculate body
Chromatic adaptation
Received from Prof. Hunt
Parsing of information
Visual areas of the cortex
Brightness – luminance L+M signals: luminance like All three cones participate in brightness
perception Possible rod contribution to brightness Intrinsically photosensitive Retinal Ganglion
Cells might contribute too by pupil diameter regulation
Rod vision -> scotopic and peripheral vision
Mesopic vision: interaction between rod and cone receptors
Brightness description
CIE supplementary system of photometry, CIE 200:2011
Helm holtz-Kohlrauscheffect
Purkinje effect
Equivalent luminance, Leq
a = 0.05 cd/m2, b = 2.24 cd/m2, k = 1.3, f(x,y)=Nakano (1999)Parameters:
a =L + a
L
(adaptation coefficient; achromatic)
Photopic luminance
L
Scotopicluminance
L'
(L') · (L) ·101-a a cac =
L1/2 + bkL1/2
(adaptation coefficient; chromatic)
c =ac · f(x,y)
Cr/gCy/b
Scotopic system Photopic systemV'(λ )input z(λ )inputy(λ )inputx(λ )input
c = ac [ f(x,y) - 0.078]
Luminance and brightness
-20,00
0,00
20,00
40,00
60,00
80,00
100,00
120,00
140,00
160,00
400 500 600 700
wavelength, nm
rel.
resp
. V(l)
Vb2(l)
Landolt1,2,4,6
Sp. sensitivity of different receptors
47
350 400 450 500 550 600 650 70000.10.20.30.40.50.60.70.80.9
1
Gall-Circl¯(λ)m¯(λ)s¯(λ)
wavelength, nm
rel.
sens
itiv
ity,
arb
. uni
ts
Binary – broad band match
Broad-band: tunable LED source (curtasy of Zumtobel) with 470 nm blue component
Two component: cyan + deep red LED
25 observers
48
400 450 500 550 600 650 7000.000.100.200.300.400.500.600.700.800.901.00
2LED Zumtobel
wavelength, nm
rel.
inte
nsit
y, a
rbitr
. uni
ts
Matching point of binary-broad-band match
49
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
x
y
View of the double booth
50
Non-fluorescent white paper placed on black background, no colour in field of view.
Relative power in the circadian-, S-cone and Rod sensitivity bands comapred to the luminous flux
51
LED source Circadian/lum.flux S-cone/lum.flux rod/lum.flux
2 LED combination 0,73 0,22 1,1Zumtobel
adjustable source0,39 0,23 0,56
Results of brightness comparison of 2 LED and “Zumtobel” source illuminated samples
Number of Persons 4 (1<35Y,0>65Y)
15
(1<35Y,4>65Y)
6 (1<35,1>65Y)
Rel. brightness (2 LED/”Zumt.”
0,86 1,20 1,02
% st. dev. 2,1 9,9 3,1
Observers found chromatic mismatch for equal chromaticity and luminance setting (Instr. Syst. CAS 140CT+TOP100 radiance probe)
Visual acuity Landolt-C investigation The fovea is also in the mesopic range V()
sensitive Subjective evaluation is mainly based on
foveal vision
Summary Foveal task: V() Peripheral task: V´() Brightness evaluation:
Equivalent luminance
Colour deficiencies Dichromat
protanope deuteranope tritanope
Anomalic trichromat protanomal deuteranomal tritanomal
Monochromat cone monochromat rod monochromat
Normal trichromat
Dichromat
Red-green colour deficient: cone density normal, but has only S and M cones
Dichromat
Red-green colour deficient : cone denstiy only 35 % of normal, has only S and L cones.
Rod achromat
Congenital rod achromat
1,00 % 0,02 %
1,10 % 0,01 %
0,002 % ? %
Basic forms of colour deficiency
ProtanópiaDeuteranó
pia
Tritanópia
Ishihara test
8 % of males is colour deficient, in case of females it is only 0,4 %.
With regard to the colour deficient!
Normal
Deuteranop
Old coloratio
n
Modern coloratio
n
Thanks for your kind attention!
This publication/research has been supported by the TÁMOP-4.2.2/B-10/1-2010-0025 project.