What Is Color? How Brains Make Color Sensations Contents Abstract ............................................................................................................................................... 4 Keywords ............................................................................................................................................ 4 1. Anatomy .......................................................................................................................................... 5 1.1. Eye ........................................................................................................................................... 5 1.1.1. Eyeball layers .................................................................................................................... 5 1.1.2. Eyeball front...................................................................................................................... 5 1.1.3. Fluids................................................................................................................................. 5 1.1.4. Eye muscles ...................................................................................................................... 5 1.1.5. Eyelids............................................................................................................................... 5 1.1.6. Retina ................................................................................................................................ 5 1.1.6.1. Receptors.................................................................................................................... 6 1.1.6.2. Cones.......................................................................................................................... 6 1.1.6.3. Color-receptor array ................................................................................................... 7 1.1.6.4. Retinal cells ................................................................................................................ 7 1.1.6.5. Ganglion cells ............................................................................................................ 7 1.2. Brain ......................................................................................................................................... 8 1.3. Evolution .................................................................................................................................. 8 2. Physiology....................................................................................................................................... 8 2.1. Receptor processing ................................................................................................................. 9 2.2. Retinal processing .................................................................................................................... 9 2.3. Brain processing..................................................................................................................... 10 2.3.1. Occipital lobe .................................................................................................................. 10 2.3.2. Temporal lobe ................................................................................................................. 10 2.3.3. Parietal lobe .................................................................................................................... 11 2.4. Intensity.................................................................................................................................. 11 2.4.1. Luminance....................................................................................................................... 11 2.4.2. Brightness ....................................................................................................................... 11 2.4.3. Color lightness ................................................................................................................ 12 2.4.4. Contrast ........................................................................................................................... 13 2.4.5. Dark Adaptation .............................................................................................................. 13 2.5. Hue ......................................................................................................................................... 13 2.5.1. Color frequencies and wavelengths ................................................................................ 14 2.5.2. Spectral colors ................................................................................................................. 15 2.5.3. Color differences ............................................................................................................. 16 2.5.4. Color opponencies .......................................................................................................... 16 2.5.5. Univariance ..................................................................................................................... 18 2.5.6. Color spaces .................................................................................................................... 18 2.5.7. Color wheels ................................................................................................................... 19 2.5.8. Mixing Colors ................................................................................................................. 20 2.5.8.1. Complementary colors ............................................................................................. 20 2.5.8.2. Grassman laws ......................................................................................................... 21 2.5.9. Adjacent colors and contrast ........................................................................................... 21 1 2.6. Saturation ............................................................................................................................... 21 2.7. Contours ................................................................................................................................. 22 2.8. Filling-in ................................................................................................................................ 22 2.9. Depth Perception .................................................................................................................... 23 2.9.1. Stereoscopy ..................................................................................................................... 23 2.9.2. Retinal size ...................................................................................................................... 23 2.9.3. Distance calculation ........................................................................................................ 24 2.9.4. Depth Cues ...................................................................................................................... 24 2.10. Eye Movements ................................................................................................................... 25 2.10.1. Blinking......................................................................................................................... 26 2.10.2. Saccade ......................................................................................................................... 26 2.11. Fixation ................................................................................................................................ 27 2.12. Focusing ............................................................................................................................... 27 2.13. Viewpoint ............................................................................................................................. 28 2.14. Visual search ........................................................................................................................ 28 2.15. Location perception ............................................................................................................. 28 2.16. Size perception ..................................................................................................................... 28 2.17. Texture Perception ............................................................................................................... 28 2.18. Pattern Recognition .............................................................................................................. 29 2.18.1. Neurons ......................................................................................................................... 30 2.18.2. Number perception........................................................................................................ 30 2.18.3. Shape perception ........................................................................................................... 30 2.18.4. Scenes ........................................................................................................................... 32 2.18.5. Mathematical methods .................................................................................................. 33 2.18.6. Algorithms .................................................................................................................... 33 2.18.7. Production systems ......................................................................................................