Colour vision János Schanda Virtual Environments and Imaging Technologies Laboratory University of Pannonia

Overview Human trichromacy Human trichromacy The human retina The human retina Colour deficiencies Colour deficiencies Path from the retina to the cortex Path from the retina to the cortex Brightness versus luminance Brightness versus luminance The fifth light sensitive cell in the human retina The fifth light sensitive cell in the human retina

Visibility Perceiving details Perceiving details Rapid identification Rapid identification Brightness/lightness evaluation Brightness/lightness evaluation Hue & colourfulness evaluation Hue & colourfulness evaluation

The eye

The structure of the eye

The human eye Fovea: 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 Imaging the exterior world on the retina The retina and its most sensitive part the fovea The retina and its most sensitive part the fovea The receptive cells 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

Fundamental colour matching experiment Wright and Guild experiments Wright and Guild experiments Different fundamentals Different fundamentals Transformed to common basis Transformed to common basis

R, G, B primary based CMFs R: 1 unit, 700 nm R: 1 unit, 700 nm G: 4,5907 units, 546,1 nm G: 4,5907 units, 546,1 nm B: 0,0601 units, 435,8 nm B: 0,0601 units, 435,8 nm

Background information CIE ° standard colorimetric observer and Colour Matching Functions (CMFs) CIE ° standard colorimetric observer and Colour Matching Functions (CMFs) CIE 1924 spectral luminous efficiency function CIE 1924 spectral luminous efficiency function CIE ° standard colorimetric observer and CMFs CIE ° standard colorimetric observer and CMFs

CIE TC 1-36 report Fundamental Chromaticity Diagram with Physiological Axes - Part 1: CIE 170:2006 Fundamental Chromaticity Diagram with Physiological Axes - Part 1: CIE 170:2006 L,M,S cone fundamentals L,M,S cone fundamentals Photopigment absorption spectrum Photopigment absorption spectrum Macular pigment absorption Macular pigment absorption Field size dependence Field size dependence

Sties-Burch colour matching functions

Macular pigment optical density

Lens and ocular media optical density

Derived photopigment low density absorbance

Complete path of getting to the corneal level cone fundamentals

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 CIE 2° and cone fundamental derived (CFD) 2° CMFs

Standard and cone fundamental chromaticity diagram (Insert:  E per wavelength)

D(u’,v’) differences if the CIE 2° observer is used or the tentative CMFs of CIE TC 1-36 CIE ° CFD-CMF 10,0250,011 20,0380,013 30,0250,010 40,0130,005 50,0030, ,003 70,0170,009 80,0020,003 90,0060,004 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)

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 wavelength, nm rel. sensitivity V(l) VM(l) V´(l) y(l)10

Neural pathways -2 Parvocellular: L-M cone signal Parvocellular: L-M cone signal Fine details, slow Fine details, slow Red – green antagonistic structure Red – green antagonistic structure Koniocellular: S – L, M-S cone signals Koniocellular: S – L, M-S cone signals Slow Slow Yellow – blue antagonistic structure 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 L+M signals: luminance like All three cones participate in brightness perception All three cones participate in brightness perception Possible rod contribution to brightness Possible rod contribution to brightness Intrinsically photosensitive Retinal Ganglion Cells might contribute too by pupil diameter regulation Intrinsically photosensitive Retinal Ganglion Cells might contribute too by pupil diameter regulation Rod vision -> scotopic and peripheral vision Rod vision -> scotopic and peripheral vision Mesopic vision: interaction between rod and cone receptors Mesopic vision: interaction between rod and cone receptors

Brightness description CIE supplementary system of photometry, CIE 200:2011 CIE supplementary system of photometry, CIE 200:2011

Luminance and brightness

Sp. sensitivity of different receptors 47

Binary – broad band match Broad-band: tunable LED source (curtasy of Zumtobel) with 470 nm blue component Broad-band: tunable LED source (curtasy of Zumtobel) with 470 nm blue component Two component: cyan + deep red LED Two component: cyan + deep red LED 25 observers 25 observers 48

Matching point of binary-broad- band match 49

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 sourceCircadian/lum.fluxS-cone/lum.fluxrod/lum.flux 2 LED combination0,730,221,1 Zumtobel adjustable source 0,390,230,56 Results of brightness comparison of 2 LED and “Zumtobel” source illuminated samples Number of Persons 4 (1 65Y) 15 (1 65Y) 6 (1 65Y) Rel. brightness (2 LED/”Zumt.” 0,86 1,201,02 % st. dev.2,19,93,1 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 V( ) Foveal task: V( ) V´( ) Peripheral task: V´( ) Brightness evaluation: Equivalent luminance

Colour deficiencies Dichromat Dichromat protanope protanope deuteranope deuteranope tritanope tritanope Anomalic trichromat Anomalic trichromat protanomal protanomal deuteranomal deuteranomal tritanomal tritanomal Monochromat Monochromat cone monochromat cone monochromat rod 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 Protanópia Deuteranópia 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 coloration Modern coloration

Thanks for your kind attention! This publication/research has been supported by the TÁMOP-4.2.2/B-10/ project.