Color Management for Production Printing

1. Color Management for Production Printing Connectivity Master Full Training Module Created by: Group L&D Version:1.1.a Classification: Ricoh Family Group Internal use only

2. Objectives • After completing this training you should be able to explain: • the basics of color management. • some of the terminology used in production color printing.

3. Requirements • PC running Windows. • This presentation.

4. Pre-requisites and exam • There are no pre-requisites. • At the end of this course, you can do the exam on WICE.

5. Module Overview • Introduction • What is Color • Describing Color • Color Management • Color Management Systems • Proofing • Profiling

6. 1. Introduction

7. Introduction to Color Management • Color is important to businesses based on their specific needs. • For instance, many organizations have a corporate or brand color that is a key element of their brand identities. • These colors must be accurately reproduced, regardless of whether or not the branded items are printed using offset or digital printing or other technologies. • However, to achieve this accurate reproduction, people have to rely on color management, which has always been regarded as something difficult and only for color geeks. • This presentation will show you the fundamentals of color and color management in, hopefully, an easy way. • It will define color terms and it will explain the tools and processes behind color reproduction.

8. 2. What is Color

9. Color Basics • Color is the visual sensation produced in response to selective absorption of wavelengths from visible light. • To see an object it must either emit light, as the sun does, or reflect it from another source, such as the moon reflecting sunlight. • Color is generally described using additive or subtractive models.

10. Light • So what exactly is light? • Light is actually a form of electromagnetic radiation. • What is electromagnetic radiation, then? • Electromagnetic radiation has a dual nature as both particles and waves, as explained on the next slides.

11. Electromagnetic Wave • The traditional way is to describe light as being an electromagnetic wave. • This wave has amplitude, which is the brightness of the light, wavelength, which is the color of the light, and an angle at which it is vibrating, called polarization. • The wave theory of light was happily adopted and accepted until it was found to fail to explain some observed and measured phenomena.

12. Quantum Theory • In terms of the modern quantum theory, electromagnetic radiation consists of particles called photons. • Photons are packets ("quanta") of energy which move at the speed of light. • In this particle view of light, the brightness of the light is the number of photons, the color of the light is the energy contained in each photon, and four numbers (X, Y, Z and T) are the polarization.

13. Electromagnetic Spectrum • Both interpretations are correct, but the wave viewpoint is primarily used, since it is a more useful description. • The human color perception range is between ultraviolet (400nm) and infrared (700nm).

14. White Light • Sir Isaac Newton was the first to realize that white light actually contains all colors. • A nice tool to show that is the prism.

15. RGB • Light with a wavelength between 600 and 700 nm is known as red light. • Light with a wavelength between 500 and 600 nm is known as green light. • Light with a wavelength between 400 and 500 nm is known as blue light. Green Blue Red 700 400 500 600

16. Seeing Color • When we see light, there are 3 important elements that influence color perception: • The light source. • The colored object. • The eye. Light sensor (human eye) Light source Colored object

17. Eye Mechanism • Eyes have a structure similar to cameras. • Two types of light-sensitive cells in the retina: rods and cones. • There are three types of cone cells, each sensitive to a specific range of wavelengths (red, green and blue).

18. Reflected Light Transmitted Light Perceiving Colors • We can see: • reflected light(intrinsic color). • transmitted light (luminous color) • Color is perceived by the reflection of light off an object. • The way a color looks is relative to the viewer.

19. Color Perception (1/2) • The light source emits light. • This is known as luminous color. • The object absorbs colors and reflects colors. • The human eye perceives color based on the objects that light is reflected from. • This light is known as intrinsic color.

20. Color Perception (2/2) • Perception of colors depends on: • The light-source. • The observer. • the surrounding colors.

21. The light source • The color of a light source is described by its temperature. • Color temperatures are measured using the Kelvin scale. • Warmer temperatures emit bluish light. • Cooler temperatures emit reds.

22. Metamerism • Metamerism is an illusion in which two or more colors appear identical under certain light sources, but are different from each other under other lights or to a different observer. • This is a common problem in the color printing business. • That is the reason why many professionals use a light cabinet to evaluate their prints. Light cabinet

23. Fluorescence • Some atoms and molecules have the ability to absorb photons of a certain energy level, and emit photons of a lower energy level. • This is called fluorescence, and can sometimes change one type of visible (or even invisible  ultraviolet) wavelength into another visible wavelength. • Many paper manufacturers add fluorescent brighteners (optical brighteners or bluing agents) to whiten the slightly yellowish paper. Paper with optical brighteners, seen using a black light

24. Additive Colors (RGB) • By combining Red, Green and Blue light we can create all the colors of the visible light-spectrum.

25. RGB Color Monitors CRT LCD

26. Subtractive Colors (CMY) • Using Cyan, Yellow and Magenta toners we can create colors on paper.

27. Complementary Colors • In the color theory, two colors are called complementary if, when mixed in the proper proportion, they produce a neutral color (grey, white, or black). • Red is the complement color of cyan. • Green is the complement color of magenta. • Blue is the complement color of yellow. R G B C M Y

28. White Paper Reflection • In theory, white paper reflects all colors. • This is a theoretical statement, because different brands of paper have a different color. • This is why in color management it is very important to know what paper we are using. • This is not only true for the output, but also for the original.

29. Y R C M G B Yellow Toner Absorbs Blue Light • Yellow is the complement of blue. • Yellow toner absorbs blue light and reflects green and red light. • The reflected “G” and “R” light are seen as yellow. R G B C M Y

30. Y R C M G B Magenta Toner Absorbs Green Light • Magenta is the complement of green. • Magenta toner absorbs green light and reflects blue and red light. • The reflected “B” and “R” light are seen as magenta. R G B C M Y

31. Y R C M G B Cyan Toner Absorbs Red Light • Cyan is the complement of red. • Cyan toner absorbs red light and reflects green and blue light. • The reflected “B” and “G” light are seen as cyan. R G B C M Y

32. Mixing Subtractive Colors • Equal amounts of magenta and yellow toner produces red. • Equal amounts of cyan and yellow toner produces green. • Equal amounts of magenta and cyan toner produces blue. Y C M

33. Process Black • In theory, equal amounts of C, M and Y produce black. • This black is called “Process Black”. • In reality, it is virtually impossible to produce true black using cyan, magenta and yellow toner. • Depending on the used toners or inks, the result can vary form deep blue to be brown or gray. Pure black Process black

34. Under Color Removal (UCR) • One way of reducing the “Process Black” problem is UCR or Under Color Removal. • UCR replaces an equal amount of yellow, cyan and magenta with black toner, but only in dark, near neutral colors. • Advantages: • Lower toner consumption. • Better reproduction of black. • Disadvantage: • The image lacks depth if high UCR ratios are used like in Letter Mode. • That is the reason why 100% UCR is not used very often. 100% UCR 60% UCR

35. Gray Component Removal (GCR) • GCR has the same function as UCR. • The difference between GCR and UCR is that GCR starts at lower image densities. • It can be used for neutral and non-neutral colors that are either light or dark

36. UCR vs GCR UCR • The pictures show the difference between UCR and GCR. • You can clearly see that GCR starts earlier with color replacement. GCR

37. 3. Describing Color

38. Chapter Overview • Introduction to Describing Color • Color Wheels • HSB/ HSL • Named Colors • Spot Colors • CIE Color Model

39. 3.1 Introduction to Describing Color

40. Describing Color • Color is often difficult to communicate about. • The reason is that the words we use to describe color are vague and frequently misunderstood. • Not only are technical terms such as "value," "saturation" and "chromaticity" confusing but even simple words such as "bright," "pure," "shiny" and "dim" are hard to use accurately. • Even the experts struggle without a set of standardized definitions. • We need numerical models to manipulate and predict colors, simply because we use computers.

41. Color Models • Both scientists and artists have long struggled to come up with a model that would be able to describe al colors. • Famous people like Newton, Goethe and Maxwell have tried. • Some modern models are based on the Munsell Color System, developed by Albert H. Munsell. • His model uses different values of hue, brightness (value), and saturation (chroma) to define colors more accurately.

42. Color Terminology – Hue • Hue is the property of color that we are actually asking about. • For example, when we talk about colors that are red, yellow, green, and blue, we are talking about hue. • Different hues are caused by different wavelengths of light. • Therefore, this aspect of color is usually easy to recognize. Hue Contrast – different hues Hue Constant – different colors, same hue

43. Color Terminology – Chromaticity • Chromaticity describes the purity of a color. • That means there is no white, black, or gray present in a color that has high chroma. • These colors will appear vivid and pure. • Chromaticity is related to and often confused with saturation. High chroma – very shiny and vivid Low chroma – achromatic, no hue Constant chroma – medium chroma, similar vividness, less purity than top image

44. Color Terminology – Saturation • Related to chromaticity, saturation tells us how a color looks under certain lighting conditions. • For instance, a room painted a solid color will appear different at night than in daylight. • Over the course of the day, although the color is the same, the saturation changes. • This property of color can also be called intensity. Saturation constant – same intensity, different hue Saturation contrast – various levels of fullness, same hue

45. Color Terminology – Value • When we describe a color as "light" or "dark", we are discussing its value or "brightness“, “lightness” or “luminance”. • This property of color tells us how light or dark a color is based on how close it is to white. Low Value, Constant – same brightness level Contrast of Value – grayscale= no chroma Contrast of Value – big differences in brightness

46. Brightness or Lightness • In color science, there is a distinction between lightness and brightness, although the 2 words mean the same. • The strict definition of lightness: lightness is the brightness of an object relative to an absolute white reference. • This means that lightness ranges from dark to light, with specific definitions of black and white as the limits. • We can measure lightness and assign specific numerical values to it. • Brightness ranges from dim to bright with no real limits. • It is just a subjective sensation in our heads. HSL and HSB are derived from the Munsell Color System, describing Lightness and Brightness

47. 3.2 Color Wheels

48. Color Wheels • The color wheel or color circle is the basic tool for combining colors. • The first circular color diagram was designed by Sir Isaac Newton in 1660. • The color wheel is designed so that virtually any colors you pick from it will look good together. • Over the years, many variations of the basic design have been made, but the most common version is a wheel of 12 colors based on the RYB (or artistic) color model.

49. 3.3 HSL and HSB

50. HSL and HSB/HSV • Derived from the Munsell Color System are the HSL and HSB models. • They are the two most common cylindrical-coordinate representations of points in an RGB color model. • HSL stands for hue, saturation, and lightness, and is often also called HLS. • HSB stands for hue, saturation, and brightness, and is also often called HSV (V for value). • The major difference is in the shape of the 2 models. • HSB uses 1 cone to display all colors, while HSL uses 2 cones.