The Principles of Chromatics

1. The Principles of Chromatics

2. Light • Electromagnetic radiation, that produces a sight perception when being hit directly in the eye • The wavelength of visible light is 400 - 700 nm

3. Visible Light

4. The prism divides the light into its different wavelength components

5. Color • Subjective impression • Different wavelengths cause different color perceptions • The short cause blue and the long cause red 400 700 nm

6. Group discussion 1 • Which things have an effect to perceiving a color?

7. The Perception of Color You need three elements to perceive colors • LIGHT • wavelength • intensity • direction • TARGET • Selective reflection • wavelength • intensity • direction • PERCEIVER • Color stimuli • physiological color perception • Psychological color perception

8. The Color of an Object • The color effect caused by the light that the object emits Kuva:Creo

9. Target Color Stimulus • The color is determined by the stimulus that is directed to the eye that depends on the light source's spectral power peak S ( ) and the target's reflection spectre R (  )

10. The Eye's Color Vision • Part of the light travels to the retina where light sensitive cells react to the light stimulus by transferring the stimulus-like signal from retina to the brain • Retina has two kinds of cells that react to the light stimulus

11. Kuva:Agfa

12. Retina has two kinds of cells that react to the light stimulus • ROD CELLS • Distinguishes the differences in lightness • RETINAL CONES • - cones; different spectral sensitiveness • Color vision

13. Color sensitive retinal cone

14. Kuva:Agfa

15. Spectral sensitivities of retinal cones

16. Contributing factors of Color perception • Memory • Background color and brightness • Adaptation of the eyes • Lighting • diffusion/direct lighting • Color surface area

17. Effects of background colors

20. Color temperature • Light is characterized as color temperature • The temperature of an ideal radiator radiating a specific colored light (black-body, Planck radiator) • Presented as Kelvin-degrees (K) ; Kelvin = oC +273

21. As the temperature changes the level of radiation energy and its spectral distribution (color) changes

22. Color Temperature • The color temperature describes the color of the light emitted by the source • The color temperature represents the temperature of the emitting black body in K-degrees • candlelight ~ 2000 oK • blue sky 12 000-18 000 oK • daylight ~ 5000 oK

23. Color temperatures of the CIE standard ligth sources • A 2800 oK ( tungsten lamp) • B 4900 oK ( sun) • C 6700 oK ( northern sky) • D 65 6500 oK ( northern sky + UV) • D 50 5000 oK ( white light, gas lamp)

24. Metameria • Two colors, with different spectral remission curves may look similar • Two colors may look similar in one lighting and totally different in another

25. Chromatic colors • Colorful colors • Colors with tone

26. Achromatic colors • Black, white, gray • Neutral colors • No tone

27. The reflection spectre of color • spectral sensitivity distribution of light reflected from a lighted surface

28. Color models, representations of color • Visual color • The technical representation of color • additive color formation • subtractive color formation • Colorimetric color definition • Indexed color representation • Color maps

29. Group discussion 2 • What color systems you know?

30. Visual color • psychophysical, subjective impression • The human eye senses the color of electromagnetic radiation depending on its wavelength • Short wavelengths as blue, long as red

31. Additive Color Formation • additive • The desired color is generated by mixing lights of different colors • The starting point is black; red, green and blue color is added to get white • Primary colors R,G,B • Secondary colors C,M,Y • In TV-and computer monitors

32. The additive color mixing

33. Subtractive Color Formation • subtractive • The starting point is white • subtracting red,green, blue to get black • Subtraction with filters that are printing ink layers • Filtering is made with pigments which are the opposite colors of the filtered colors • Primary colors cyan, magenta and yellow

34. The starting point in substractive color formation is white

35. Kuva:Creo

36. Group discussion 3 • What wavelength has to be absorbed in order to produce • -yellow? • -cyan? • Which pigments have to be combined in order to produce red color?

37. magenta cyan yellow black Subtractive color formation

38. Subtractive color mixing

39. Colorimetric color definition • Tries to define the color as the eye perceives it • components • HUE • SATURATION • LIGHTNESS

40. The Colorimetric components of Color • HUE • impression of color • the “name” of color • SATURATION • the intensity of color • purity • 0 on gray, white and black • LIGHTNESS • total reflection • high with white and yellow colors • low with black

41. Hue Saturation Luminance Visual scales of Hue, Saturation and Luminance - components of color

42. Selecting colors using the HSL color model in Adobe Photoshop

44. Kuva : Agfa

45. CIELab • Mathematical conversion from CIEXYZ • parameters • L = lightness • a = chromaticity in red-green-axis • b = chromaticity in yellow-blue- axis

47. Indexed color presentation • The colors are presented with predefined color palette's colors

48. Indexed color specification in Photoshop

49. Color Maps • The colors are presented with the help of reference map's model colors e.g. PANTONE; Focoltone

50. Pantone Color specification in Photoshop