1. 1 The Eye and Colour Vision By Michael Harwood updated Feb 2012

2. 2 Contents Parts of the eye Requirements for vision Retina & rhodopsin Spectral response  colour vision Experiments to try Colour addition and “subtraction” Age effects, optical illusions,...

3. 3 The Human Eye

4. 4 Minimum Requirements for vision  very transparent cornea  very transparent lens  very transparent vitreous & aqueous humor  curved cornea  light sensitive cells we have two types with 4 colour sensitivities!  nerve cells & optic nerve

5. 5 Minimum Requirements (continued...)  lens and humours must have different indices of refraction  eyelids  tearducts  lens focused to some useful distance  process of removing dead cells so that they don’t clog up the eye

6. 6 Extra features ! Human eyes also have:  recessed eyes (protected by bones)  colour vision  vision over huge range of light intensities  moveable iris that controls amount of light  lens that can change focal length  eyebrows – keep water out of eye  eyelashes?

7. 7 Extra features (continued...)  automatic feedback - focussing - iris - tracking - saccades and  -sac (to prevent fatigue)  binocular vision (two eyes on front of head)  excellent focus at fovea -- able to read text  colored iris – beauty (and prevention of scattering)  macula lutea – more UV protection on fovea

8. 8 Retina

9. 9

10. 10 Rods

11. 11 Rhodopsin Rhodopsin is based on 11-cis-retinal + an opsin molecule. Retinal is based on Vitamin A. Maximum sensitivity at 498 nm

12. 12 Rhodopsin

13. 13 Rods vs Cones ConesRods Require a lot of light to work. Sensitive to low light; overpowered by normal light Detect colour (3 types)Only shades of gray Mostly near foveaMostly In periphery

14. 14 Fovea vs Periphery

15. 15 Spectral Sensitivity

16. 16 Spectral Response

17. 17 Primary Colours: R,G,B R+G = Y G+B = C B+R = M R+G+B = White

18. 18 Colour "Subtraction" Secondary colours

19. 19 CIE chromaticity diagram

20. 20 Gamut