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ColorSync

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ColorSync is Apple’s system-level software to help you manage the color of your documents and devices. Mac OS users can streamline their publishing process using a control panel, AppleScripts and profiles. The result is powerful control over color matching at every step of the workflow process.

Introduction

ColorSync is the industry-standard tool for managing color across input, display, and output devices. This system-level software developed by Apple Computer works with scanners, digital cameras, monitors, printers, copiers, proofers, and presses. ColorSync is also supported in all leading image-editing and page-layout applications.

Anyone responsible for creating print or electronic materials knows how important accurate color can be in conveying information and creating desired responses. They also know how difficult it has been to manage color. A shift in color can seriously damage the effectiveness and accuracy of a product photo or design. Incorrect colors can cause lost sales; mail-order customers often return items because they don’t match the colors in the catalog or on the web site.

ColorSync saves time and money by enabling you to accurately capture, edit, preview, and output color documents. It gives you powerful control over color matching at every step of the workflow process by using unique "profiles" to describe the difference in color performance between what an input or output device does and what we know it should do. These profiles are usually stored as part of an image file (in the file’s header or "table of contents") and provide a description of how this image was captured, what its color space is, and more.

ColorSync calls upon the computational power of "CMMs" (color matching modules) which convert images from one color space to another—for example, from RGB to CMYK—and simultaneously apply the information in the profile to correctly render the image.

In each step of the workflow, ColorSync compensates for any deviations in the image-capturing systems of scanners, the display anomalies of monitors, and the color imaging components of printers and output devices. The CMMs from such highly respected color partners as Heidelberg Prepress, Kodak, and Agfa are packaged in each version of ColorSync along with a unique CMM from Apple Computer.

ColorSync also includes a powerful but easy-to-use monitor calibration system which corrects any irregularities in the monitor’s age, phosphor set, ambient light, white point, or monitor type. ColorSync lets you calibrate your computer’s monitor so that the colors of a displayed image correspond to the original photograph or digital capture. You can even view an image as it would appear on different paper stock or output devices (called a "soft proof"). And, when you use ColorSync to simulate a specific printing press or film recorder, the proof prints you make on a color desktop printer can be amazingly close to the color of the final output.

ColorSync is not "all or nothing." You can choose to only calibrate your monitor, or only calibrate your scanner, or you can implement an entire ColorSync workflow. Each incremental step means time savings, reduction of waste, and added profits.

With ColorSync software, anyone who works with color content can maintain quality throughout a wide array of output media including newspaper photographs, magazines, catalogs, books, web pages, videos, QuickTime movies, photo transparencies, and more. Because ColorSync works directly with the Mac OS and has an open architecture, hardware and software manufacturers have been able to add ColorSync support to their products easily. In fact, more than 100 products ranging from inexpensive scanners to top-of-the-line printing presses now take advantage of the powerful ColorSync color management capabilities. With ColorSync, any color-aware application or device can communicate with any other. With so many products for Mac OS systems now supporting ColorSync, you can finally achieve consistent color at every step of your workflow, from input and output.

The Basics of Color Systems and Color Management

Traditional printing professionals will most likely tell you that they have been doing color management for years. They’ll say they’ve been getting customer-correct color off their printing presses and scanners, that they’ve been proofed accurately by a highly experienced press operator.

Traditionally, designers have sent their color projects to the printer. What did the printer do with these projects? They reworked and translated the designer’s intended colors into the capabilities of their printing facility. Color management has been a sort of imprecise magic.

Enter ColorSync: ColorSync puts the color control back in the hands of the designer, while offering an unprecedented level of color fidelity across media.

Rotating ColorSync ColorSync is system-level "digital glue" which allows peripheral devices, the operating system and applications to communicate. ColorSync acts as a common interpreter of color—from scanner to display to application to printer.

To accomplish this requires system-level knowledge of the color characteristics of each device. These characteristics are described in the device's profile. Profiles are used to show, for example, how a monitor displays a particular color, and this information can be used by a proofing device or printing press to reproduce that same color.

Scanner operators no longer need to stand in front of a large, expensive device, tweaking buttons to get as close as possible to the proper color. Now you can buy off-the-shelf, affordable products that’ll create the profiles needed by ColorSync to produce correct color.

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ColorSync is system software that provides a comprehensive framework for exchanging and matching color information between input devices, displays, applications and output devices, all of which have quite different methods for representing color information.

To truly understand this process, it is necessary to have a basic knowledge of color.

The Evolution of Color

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In 1984, desktop publishing started a revolution in the production of artwork for printing.

As creative people began adopting the Macintosh, their artistic abilities blossomed. They used more images and better type fonts; they added graphics and illustrations to their documents to make everyday work look dramatically better. As quality work could be achieved more easily than ever before, the business of design flourished.

Where a document would have been typed in 1984, it was typeset in 1985, illustrated with compelling graphics in 1986, had photos added in 1989 and was printed in full color in 1991.

Color commands attention and gets better results. Color is very much a part of the fabric of commerce. Yet color alone is not satisfactory. We want quality color, color that matches the original, color that is reliable, color that is affordable.

When you add ColorSync to your production methods, you are turning the management of color into a new business. With this new business, you’ll meet new customers and be able to do more work for your existing customers.

Managed color makes for work that is more profitable, more repeatable, and much easier to achieve than ever before.

A Brief Overview of Color

Color is created through the interaction of light, an object, and the eye. There must be a light to illuminate the object. White light contains many different colors of light. This can be seen by observing how sunlight is broken into its components when passed through a prism. The resulting rainbow represents the "visible spectrum" consisting of the colors that can be seen by the eye. Each color of light has a particular wavelength. An object appears to be a certain color because it has pigments that absorb some of the wavelengths of the light that illuminates it while reflecting others back to the eye.

In other words, the color of the "green" butterfly or the "blue" sweater "happens in our mind" after our visual sensory system responds to the wavelengths of light.

Color Perception

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Our eyes contain sensors which respond to different wavelengths of light. The human visual system works quickly to respond to all the potential wavelength information. It efficiently breaks down the visible spectrum into the three primary regions of red, green, and blue. The eye contains three types of cone receptors. Each receptor is sensitive to about one-third of the visible spectrum. These are red light, green light, and blue light.

The color the eyes see in an object depends on how much red, green and blue light is reflected to the eye. Black is perceived when no light is reflected to the eye. When red, green, and blue lights are reflected to the eye in equal amounts, then white is perceived.

What you see is not always what's there! Many factors can affect our perception of color. For example, about 10% of all men are color blind and about 1% of all women are color blind. A person who looks at color for a long period of time is going to experience retinal fatigue and the colors are not going to be perceived accurately any longer. We need a standard specification system to know exactly what the color is. Lightbox

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The conditions in which color is viewed greatly affect the perception of color. For accurate viewing the light source and environment must be standardized. People in the graphic arts industry, for example, avoid fluorescent and tungsten lighting, use a standard light source, and proof against a neutral gray surface. A viewing booth, such as the Soft-View from GTI, is the easiest way to achieve standard viewing conditions.

The illustration below depicts the same photograph viewed under three different light sources. The leftmost picture is 6500 degrees Kelvin which is equivalent to department store fluorescent lighting. The middle picture is 5000 degrees Kelvin, the industry standard as far as proper viewing standards are concerned. The far right picture is 2500 degrees Kelvin (incandescent).

Color images frequently contain hundreds of distinctly different colors. To reproduce such images on a color peripheral device would be impractical. However, a very broad range of colors can be visually matched by a mixture of three "primary" lights. This allows colors to be reproduced on a display by a mixture of red, green, and blue lights or on a printer by a mixture of cyan, magenta and yellow inks or pigments.

Color Wheel Cyan absorbs red, magenta absorbs green, and yellow absorbs blue. Black is printed to increase contrast and make up for the deficiency of the inks. The illustration at the right helps us to visualize how colors of opposite hues interact.

The use of only three colors to reproduce thousands of colors is possible because the eyes are basically responsive to these three broad sections of the spectrum. The three color values constitute the specification for the matching properties of a color.

The visual sensation of color is very subjective. Each person experiences the sensation of color differently because many variables influence our color perception. Even if we did all see color the same way, we would still interpret and describe it differently based upon our individual life experience. That is one of the reasons for the development of color communication standards and easy-to-use color measurement instruments.

Hue, Saturation, and Brightness

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Color is described as having three dimensions. These dimensions are:

Hue - The name of the color.

Saturation - The degree of hue in a color, or a color's strength. A neutral gray is considered to have zero saturation. An example of color saturation is demonstrated in the red color of the butterfly wings.

Brightness - The term used to describe differences in the intensity of light reflected from or transmitted by a color image. The hue of an object may be blue, but the terms light and dark distinguish the brightness of one object from another.

Additive Versus Subtractive Color

There are only two basic methods to reproduce color - additive and subtractive. Both processes are based on the theory of using three primary colors to create all colors.

Understanding the principles of these two systems is the foundation for understanding the many aspects of the color reproduction process in printing.

Additive Color

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The additive color process begins with black, or the absence of light, and therefore no color. It involves transmitted light before it is reflected by a substrate. With transmitted light, all the colors of the rainbow can be produced by mixing the three primary wavelengths of light (red, green, and blue) in different combinations. Any two of the primary colors mixed together produces another color called a secondary color. Red and green projected together produce yellow, red and blue produce magenta, and blue and green produce cyan. Adding the three primary colors in equal amounts produces white.

Monitors, scanners, and television screens emit light. Therefore they use the additive color system. They can directly add red, green, and blue light to darkness.

A monitor blends varying intensities of red, green, and blue light at each of its pixels. These pixels are so small and close together that the eye is fooled into the perception of many different colors when there are really only three.

Let's use something you might be familiar with to illustrate the additive nature of RGB:

On-Your-Own Exercise: Use the Mac OS 8 Appearance Manager to set a new highlight color using the RGB Picker.

  1. Choose the Appearance Control Panel and select the Color icon to display the Accent Color menu.
  2. Click on the Highlight Color pop-down menu and choose Other.
  3. Select the RGB Picker and set the values to 100% red, 100 % green, and 100% blue. They produce white, illustrating the additive nature of RGB!

Subtractive Color

The subtractive color process is based on light reflected from an object which has passed through pigments or dyes that absorb or "subtract" certain wavelengths, allowing others to be reflected.

The primary subtractive colors - cyan, magenta, and yellow - can be combined to form red, green, and blue as secondary colors. Combining the ideal subtractive primaries in equal amounts produces black.

Printing is based on the subtractive color process. A printer renders color on paper or other substrates, so it must work with reflected light. To do this, printers use the opposing subtractive primaries of cyan, magenta, and yellow. When cyan, magenta, and yellow pigments are deposited on white reflective paper, each component absorbs - or subtracts - its opposing counterpart from the oncoming white light. The printing process uses cyan, magenta and yellow inks to control the amount of red, green, and blue light that is reflected from white paper. These colors are printed on paper as layers of halftone dots in varying sizes and angles to create the illusion of different colors. The effect of varying dot sizes is similar to varying intensities of a monitor's red, green and blue phosphors.

Paper itself has a significant effect on color reproduction. Since paper reflects unabsorbed light back to the viewer, the more reflective the surface, as in coated paper, the wider the range of colors that can be produced.

Let's use something you might be familiar with to illustrate the subtractive nature of CMYK:

On-Your-Own Exercise: Use the Mac OS 8 Appearance Manager to set a new highlight color using the CMYK Picker..

  1. Choose the Appearance Control Panel and select the Color icon to display the Accent Color menu.
  2. Click on the Highlight Color pop-down menu and choose Other.
  3. Select the CMYK Picker and set the values to 100% cyan, 100% magenta, and 100% yellow. They produce black, illustrating the subtractive nature of CMYK!

Color Spaces

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A color space is a model for representing color in terms of intensity values. A color space specifies how color information is represented. It defines a one, two, three, or four dimensional space whose dimensions, or components, represent intensity values. Visually, these spaces are often represented by various solid shapes, such as cubes, cones or polyhedra.

ColorSync supports several different color spaces to give users the convenience of working in whatever kind of color data most suits their needs. For example, RGB space is a three-dimensional color space whose components are the red, green, and blue intensities that make up a given color.

The ColorSync color spaces fall into several groups or base families. An additional color space, Hi-Fi color space, is primarily used in new printing processes involving the use of gold plate and silver, and also for spot coloring.

Gray Spaces

Gray spaces typically have a single component, ranging from black to white. Gray spaces are used for black-and-white and grayscale display and printing.

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RGB-Based Color Spaces

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The RGB space is a three-dimensional color space whose components are the red, green and blue intensities that make up a given color. For example, scanners read the amounts of red, green, and blue light that are reflected from an image and then convert those amounts into digital values. Displays receive the digital values and convert them intro red, green, and blue light seen on screen. RGB color spaces are additive.

RGB-based color spaces are the most commonly used color spaces in computer graphics, primarily because they are directly supported by most color displays. Because the colors produced by RGB specifications vary from device to device they are called device-dependent color spaces. Device-dependent color spaces enable the specification of color values that are directly related to their representation on a particular device.

The groups of color spaces within the RGB base family include RGB spaces, HSV spaces and HLS spaces:

RGB Spaces - any color expressed in RGB space is some mixture of three primary colors: red, green, and blue.

HSV and HLS Spaces - transformations of RGB space that allow colors to be described in terms more natural to an artist. The name HSV stands for hue, saturation, and value. HLS stands for hue, lightness, and saturation.

CMY-Based Color Spaces

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CMY-based color spaces are most commonly used in color printing systems. They are device dependent and subtractive in nature. The groups of color spaces within the CMY family include:

CMY - not very common except on low-end color printers.

CMYK - models the way inks or dyes are applied to paper in printing. The name CMYK refers to cyan, magenta, yellow, and black. Cyan, magenta, and yellow are the three primary colors in this color space. Red, green and blue are the secondaries. Theoretically black is not needed. However, when full-saturation cyan, magenta, and yellow inks are mixed equally on paper, the result is usually a dark brown, rather than black. Therefore, black ink is overprinted in darker areas to give a better appearance.

CMYK colors vary with printer, ink, and paper characteristics. In addition, different devices have different gamuts, or ranges of colors that they can produce. Because the colors produced by both RGB and CMYK specifications vary from device to device, they are called device-dependent color spaces.

Conversion from an RGB color space to a CMYK color space involves a number of variables. It involves device-specific, ink-specific, and even paper-specific calculations of the amount of black to add in dark areas and the amount of other ink to remove where black is to be printed. ColorSync performs these calculations for the user when converting among color spaces.

Device-Independent Color Spaces

Device-Independent color spaces are used mainly for color models and by the system for translating between RGB & CMYK models.

Every color monitor has its own range (or gamut) of colors that it can generate using its RGB phosphors - even monitors made in the same year by the same manufacturer. The same is true for printers and their CMYK colorants, which in general have a more limited gamut than most monitors. Because the colors produced by both RGB and CMYK specifications vary from device to device, they are called device-dependent color spaces.

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Some color spaces allow color to be expressed in a device-independent way - colors that are not dependent on any particular device. Device-independent colors, are meant to be true representations of colors as perceived by the human eye. These color representations, called device-independent color spaces, result from work carried out in 1931 by the Commission Internationale d'Eclairage (CIE) and for that reason are called CIE-based color spaces.

The goal of the CIE was to create a repeatable system of color communication standards for manufacturers of paints, inks, dyes, and other colorants.

These standard's most important function is to provide a universal framework for color matching. Device-independent color spaces are used for the interchange of color data from the native color space of one device to the native color space of another device. They represent the entire range of visible colors as translation spaces. This means that any color that is selected on a display is in the gamut of this neutral color space.

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CIE L*a*b* is a three dimensional color space that is based upon human perception of color. It is the most widely used of the CIE color spaces. L*a*b* color space is based on the theory that a color cannot be both green and red at the same time, nor blue and yellow at the same time. As a result single values can be used to describe the red/green and yellow/blue attributes.

CIE L*a*b* space represents color relative to a reference white point, which is a specific definition of what is considered white light, usually based on the whitest light that can be generated by a given device.

The CIE color spaces form the foundation of device-independent color for color management.

See Also