JPAC, April 20, 2015 Contents Human Vision

and Colorimetry • Human Hirohisa Yaguchi Graduate School of Advanced Integration Science • Various color phenomena • Colorimetry

Color imaging Color？

Sir Isaac Newton (1730) The rays are not colored.

TV (CRT, LCD, etc) Printing mixture mixture Thomas Young (1802) Trichromatic theory

RGB CMY

Joseph Carroll, Daniel C. Gray, Austin Roorda and David R. Williams, Optics & Photonics News, vol. 16, 36-41 (2005)

Why three?

Dichromat

A. Stockman and L.T. Sharp, Vision Research, vol. 40, 1711-1737 (2000) We are trichromats.

We are dichromats.

M.A. Changizi, Q. Zhang, S. Shimojo, Bare skin, blood and evolution of the primate colour vision, M.A. Changizi, Q. Zhang, S. Shimojo, Bare skin, blood and evolution of the primate colour vision, Biol. Lett., doi.10.1098/rebl.2006.0440 Biol. Lett., doi.10.1098/rebl.2006.0440

Light→Eye→Brain→Color

L w/b M r/g Le,λ S y/b http://www.psy.ritsumei.ac.jp/~akitaoka/LorealWS2005.html gray Color contrast David Hubel, Eye, Brain and Vision, Scientific American Library, 1988 http://www.psy.ritsumei.ac.jp/~akitaoka/LorealWS2005.html

http://www.psy.ritsumei.ac.jp/~akitaoka/LorealWS2005.html Color contrast and Color assimilation color assimilation

Human visual Color Vision and History of Colorimetry information processing Physiology Color Vision Model Colorimetry

Eye balls: Camera Retina • S rods and cones L M CIEXYZ (1931) Eye • Retina：High intelligent input device Retina Optic nerve Photo-sensitive sensor (rods and - cones) Retina Luminance channel and chromatic opponent color Optic Chiasm - channel (horizontal cells) Horizontal cells luminance Bipolar cells channel channels Contrast (ganglion cells) Amacrine cells CIELAB (1976) Optic tract - Ganglion cells LGN： LGN achromatic red/green yellow/blue • Magno-celluar Parvo-cellular Lateral Geniculate M-path; where? Konio-cellular nucleus - - Place, motion, depth P-path; what? Optic radiation - Primary - shape, color, texture, detail visual cortex • Visual cortex Brain Color appearance V1 brightness, , chroma CIECAM (2002) - Parietal stream V2 V4 color name, color category, etc Inferotemporal steam IT - higher levels Color matching and colorimetry Basic Colorimetry (Three colorimetric systems) Wyszecki (1973) • Colorimetry is a tool used to making a prediction on whether two of different spectral power • Physical distributions will match in color for certain given system (RGB) R+G+B L M S X Y Z conditions of observation. The prediction is made by ======determining the tristimulus values of the two visual • Physiological C L M S X Y Z system(LMS) stimuli. If the tristimulus values of a stimulus are identical Y to those of the other stimulus, a color match will be M observed by an average observer with normal color • Mathematical G vision. system (XYZ) C R L X S

Z B

Color matching and colorimetry Color matching and colorimetry

Light Cones Tristimulus values Light Cones Tristimulus values

R L X R L X Color matching Color matching

R R C G G M Y C G G M Y B B

B S Z B S Z Three factors define color Tristimulus values are obtained by the spectral power and the color matching functions.

Unrelated color (aperture color) spectral power light E(λ)

eye spectral reflectance object spectral sensitivity (vision) Related color (object color) ρ(λ) l(λ), m(λ), s(λ)

Color = Light • object • eye L = ∫E(λ)ρ(λ) l(λ)dλ M = ∫E(λ)ρ(λ) m(λ)dλ S = ∫E(λ)ρ(λ) s(λ)dλ

Color address We don’t see light but the object. CIE1931 (x, y) diagram

Blue to Black vs. White to Yellow

Advanced Colorimetry Wyszecki (1973) • Colorimetry is its broader sense includes methods of assessing the appearance of color stimuli presented to the observer in complicated surroundings as they may in occur in everyday life. This is considered the ultimate goal of colorimetry, but because of its enormous complexity, this goal is far from being reached. CIELAB (CIE 1976 L*a*b*) Non-linearity

• Color adaptation • White is always white • Non-linearity • Physical unit to psychological unit

Color opponency • Brightness (psychological unit) • Luminance and chromaticness

Intensity (physical unit)

The most advanced CIE colorimetric system Hering’s Color Opponent Theory (CIECAM02)

g

IN P U T OU T P U T

green Lu m i n a n c e of ad a p t i n g fi e l d Hu e , h L A T ri s t i m u l u s va l u e s of sa m p l e Li g h t n e s s , J X , Y , Z y yellow b CI E C A M 0 2 Brightness, Q blue T ri s t i m u l u s va l u e s of w hi t e X w , Y w , Z w Sa t u r a t i o n , s Pa r am e t e r s fo r vi ew i ng co n d i t i o n Ch r om a , C red Co l o r f u l n e s s , M

r Network of various imaging media Color communication among different imaging media

R, G, B C, M, Y (devise dependent) (devise dependent) Graphic arts Scanner Photography Devise profile Devise profile interpretation interpretation interpretation

X , Y , Z X , Y , Z common language 1 1 1 2 2 2 (devise independent) (devise independent) interpretation Television interpretation

Mobile, tablet interpretation interpretation CAM CAM Viewing condition 1 Viewing condition 2 Digital camera Printer

Color appearance, brightness, , , chroma, hue, color name, etc. (viewing condition independent)