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Colour vision

Colour vision. János Schanda Virtual Environments and Imaging Technologies Laboratory University 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.

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Colour vision

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

  2. 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

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

  4. The eye

  5. The structure of the eye

  6. 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.

  7. Artist’s view of the structure of the foveal retina

  8. Light perception • Imaging the exterior world on the retina • The retina and its most sensitive part the fovea • The receptive cells

  9. The structure of the retina

  10. Cones and rods

  11. Distribution of rods and cones within the retina

  12. Spectral sensitivity of the three cone types, logarithmic scale

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

  14. 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

  15. 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

  16. 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

  17. Sties-Burch colour matching functions

  18. Macular pigment optical density

  19. Lens and ocular media optical density

  20. Derived photopigment low density absorbance

  21. Complete path of getting to the corneal level cone fundamentals

  22. 2° cone fundamentals

  23. Spectral sensitivity of the three cone types, linear scale

  24. Transformation to XYZ-like CMFs for the 2°observer(tentative equation!)

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

  26. Standard and cone fundamental chromaticity diagram(Insert: DE per wavelength)

  27. D(u’,v’) differencesifthe CIE 2° observer is usedorthetentativeCMFs of CIE TC 1-36 Dom.wavelength: 626 nm, 525 nm, 473 nm

  28. CIE u’,v’ differencesincase of CIE 2°, TC1-36 2° (Fundamental CMFs) und modified 2° Őbserver (Mod.Fund. CMFs)

  29. 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

  30. Antagonistic colour channels and the brightness/lightiness channel

  31. 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

  32. Receptive fields, functional diagram

  33. Receptive fields

  34. Neuralsignalgeneration • 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 OFFcells) • PC: parvocellular (2 ON and OFFcells) • KC: koniocellular (2 ONcells)

  35. 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 magnocellularlayers

  36. Standardised visibility functions 1.2 V(l) VM(l) 1 V´(l) y(l)10 0.8 0.6 rel. sensitivity 0.4 0.2 0 350 400 450 500 550 600 650 700 750 800 wavelength, nm

  37. Neural pathways -2 • Parvocellular: L-M cone signal • Fine details, slow • Red – green antagonistic structure • Koniocellular: S– L, M-Scone signals • Slow • Yellow – blue antagonistic structure

  38. Way of the colour signal from the retina to the brain

  39. Lateral geniculate body

  40. Chromaticadaptation Receivedfrom Prof. Hunt

  41. Parsing of information

  42. Visual areas of the cortex

  43. 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

  44. Brightnessdescription CIE supplementary system of photometry, CIE 200:2011

  45. Luminance and brightness

  46. Sp. sensitivity of different receptors

  47. 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. Matching point of binary-broad-band match

  49. View of the double booth Non-fluorescent white paper placed on black background, no colour in field of view.

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