Copyright: © 1995 Corel Corporation. All rights reserved
Citation: © 1995 Corel Corporation. All rights reserved


Some basics in color and color theory
_Some basics in color and color theory

When learning about color management, it helps if you have a basic knowledge of how we perceive and understand color.

This section of online help provides some basic information on color and color theory, how we perceive color, and how computers cannot (and can, with our intervention) reproduce color consistently. This section includes topics on:

why we perceive color differently

the mechanics of how we perceive color

a concise primer on color and color theory

a definition of color models

how computer devices cannot reproduce color consistently, and how we use color management to overcome this.

Need more information?

Click on any of the above points to jump to the topic, or you can click here [image] to start an introduction to color and color theory.

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Each of us perceives and describes color differently (so what color is it?)

Our perception of color is influenced by many factors: differences in light source, the observer, object size, the background against which color is seen, and the direction from which the object is viewed.

For example, take any three people on a Caribbean cruise. Show them a photograph taken the day before during the market place tour, and ask the color of that beautiful blue wrap they held up for the photographer. Cerulean blue, says the first; deepest azure, says the second; blue, says the third. Go a step further: ask if the color in the photograph is the color they remember. It was deeper, says the first. More brilliant, says the second. Absolutely, says the third.

This example demonstrates that we are not very reliable as reference points for precisely defining color. Not only do we vary in our description of color, but our perception of color is influenced by ambient conditions and altered by experiences, memory, and even preconceptions.

Color desktop publishing systems have the same problems [image] although at a mechanical level, of course. You scan in a photograph and display it on your monitor, but the colors don’t ring true when compared to the original. You tinker with the monitor controls and come to a more or less satisfactory reproduction, but it still isn’t quite right. You print it anyway, and the printer reproduces colors that are not what you expected. The problem is in the same vein: different types of computer devices reproduce color in different ways, and not one of them makes a very good reference point.

However, if we come to an understanding of color and its characteristics, and of how we perceive color, we can develop a way of talking about it and compensating for the drift in our perceptions. We can also develop a mechanism through which computer devices can reproduce the colors we expect: a system of color management.

Click here [image] to read about how we see color.

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But we do see colors in the same way

While we may differ in what we see and describe as color, we do have in common the mechanics of how we see color.

Color psychology and physiology: how we perceive color

Color psychology determines our emotional response to color. This aspect of color is not terribly important in the mechanics of color management, but it does underline the need for color management: maintaining an accurate rendering of color is crucial if the psychology of color is to have full impact in our drawings and images.

Color psychology shows us the importance of correctly rendering colors associated with objects that we rely on at a very basic level: the food colors, the color of the sky and the earth, and the flesh tones. These particular examples are associated with the memory colors [image] the colors of familiar and psychologically fundamental objects. When these colors are rendered correctly, we tend to see the image as color-balanced. If a color is incorrectly rendered, we see the image as poorly reproduced even if all other colors are accurately rendered.

On the physiological side, we know that human vision is tristimulus (this characteristic was demonstrated by the light experiments of Sir Isaac Newton). The retina consists of roughly 130 million light-sensitive cells, which are either cone shaped or rod shaped. The cone shaped cells react to color, and it is believed that the cones are distributed evenly to react to one of red, green, or blue (the light primaries). For this reason, the color models we use are based on three colors. The rod-shaped cells are receptive to achromatic light only, but are much more sensitive to variations in dim light.

Human vision is extremely adaptable. Consider the following:

Human vision is capable of chromatic adaptation, in which we perceive color consistently without regard to the qualities of the ambient light. For example, a red sweater looks different when viewed indoors and outside. Another example: you cannot perceive the slight changes in a monitor’s output over time [image] even over a period of a few hours.

Human vision is sensitive to a wide range of luminance, and is very adaptable. Independent of ambient lighting, an object with less than one percent intensity compared to the brightest object in our field of view is perceived as black.

Adjacent and background colors influence our perception of an object’s color. This is known as simultaneous contrast.

We are influenced by colors seen in succession. For example, if you stare at a colored patch then look at a blank background, for a moment you can see an after-image of the patch. This is known as successive contrast.

Click here [image] to review a concise primer on color and color theory.

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A concise primer on color and color theory

If you are new to using color, here is a brief primer of some basics that are important to using color in desktop publishing and to understanding color management.

Primary colors

Primary colors are specific hues that are identified as important when understood in a particular context. The context can depend on the characteristics of light, or how colorant is used or applied. There are several types of primary colors.

Light primaries. These are the colors red, green, and blue that are used to reproduce color in radiant objects or devices, such as monitors and scanners, and can be reproduced by passing white light through a prism. Light primaries are most closely associated with the RGB color model.

Complementary primaries. These colors (cyan, magenta, and yellow) are the primaries obtained by mixing equal amounts of the light primaries. Observe that these colors correspond to the pigment and printer primaries.

Pigment primaries. These are the primary colors that we learn about in school (red, blue, and yellow) and which we used to create violet, green, and orange. They are similar to the printer primaries.

Printer primaries. These are the primary colors used by printers. There are two sets of primaries: cyan, magenta, and yellow (3-color); and cyan, magenta, yellow, and black (4-color). The black component in the second set is used to make dark colors darker and blacks blacker. These primaries are associated with three-ink (CMY) and four-ink (CMYK) printers. Printer (and pigment primaries) are most closely associated with the CMY and CMYK color models.

Psychological primaries. These colors are black, white, red, green, blue, and yellow. They are not so important in terms of the mechanics of color reproduction, but they are important in re-enforcing our expectations of color. For example, apples are typically red, and an orangish apple (and you can find them) is likely to invoke interest or wariness (or to the consumer-aware, indicates a specific brand of apple).

Components of white light

White light consists of a range of wavelengths. Visible light covers the range of wavelengths from 380 nanometers (nm) to 780 nm [image] red to violet. The spectrum of visible colors is demonstrated by directing white light through a prism to produce red, orange, yellow, green, blue, indigo, and violet. Included in this spectrum are the light primaries: red, green, and blue.

The characteristics of the light primaries can be summarized in these points:

Using varying intensities of the light primaries, you can combine two or three lights to create a broad range of colors.

Using equal intensities of two of the light primaries, you can create a complementary color which is halfway between the two source colors.

Using equal intensities of the light complementary colors, you can create white.

We can measure the intensity of each wavelength, such that the combined measurements across the spectrum of a white light source describes the spectral power distribution of that source. Different white light sources have different spectral signatures.

Temperature and spectral power distribution

The temperature of ambient lighting (the illuminant) influences how we perceive an object’s color. An understanding of temperature helps explain why the sweater that was the perfect neutral red in the store looks warmer, with slightly more orange, when you get it home. Temperature is also known as color cast, and determines the purity of a color.

Temperature refers to a quality in the light source. It is an objective measure that we use to help define a standard, since a light source, like color itself, can be difficult to define precisely. For example, daylight can vary depending on the time of day, such that daylight at noon is quite different from daylight in the late afternoon. Temperature gives us a means of quantifying this difference.

The measurement of temperature is based on a theoretical substance called blackbody which, when heated, radiates color from red at low temperature to violet at high temperature. The measurement scale is in degrees Kelvin (K). A 60-watt incandescent light bulb is measured at about 2,800K, a white fluorescent lamp at 4,400K, and noon-time sunlight (mid-summer in any temperate region) is about 5,500K.

Light sources can also be characterized by their spectral power distribution [image] the measure of intensity at each wavelength. For any light source, we can derive a graph of intensity over wavelength to give us a unique spectral signature of the light source.

Spectral signature is related to but not synonymous with temperature. Both measurements provide a means of defining the characteristics of a light source. Spectral power distribution is important as a standard developed by the Commission Internationale de l’Eclairage (CIE), which defines a set of standard illuminants under which we can measure color as well as view proofs, samples, and originals. In general, the spectral signature of a light source can be correlated to a color temperature.

These characteristics of the illuminant are related to the phenomenon of metamerism, which is described in the next section.

Spectral reflectance and transmissivity of an object

The object itself is characterized by spectral reflectance or transmissivity: does the object reflect light, or does it transmit light, and what are the characteristics?

Spectral reflectance of an object can be measured under a standard illuminant to derive a spectral reflectance graph [image] the object’s spectral signature. Spectral transmissivity can be measured through colorimeters. Some colorimeters can even compensate for the ambient lighting in which a radiant object is seen or measured.

Reflectance and transmissivity are related to metamerism, in which objects of different spectral signatures look identical under one light source but different under another. The difference is inherent in the colorants and materials used in the object, as well as the color cast of the light source. Using spectrophotometers with standard illuminants, we can measure the perceived color of objects to determine if the spectral signatures are the same.

Spectral responsiveness of the observer

Lastly, we can examine the spectral responsiveness of the observer (or receptor) [image] that is, the ability to register light across the spectrum.

Spectral responsiveness defines the range of colors that the observer or receptor is capable of registering. It is affected by the quality of the light source, differences in background color, and directional differences. The effects of the light source have been discussed above under temperature and spectral power distribution. The effects of background color are easily observed as the surrounding color interacts with our sense of the object color. Directional differences (the angle at which an object is viewed) affects color by changing how light is reflected (for reflective surfaces [image] the appearance of light and shadow) or how directly light is radiated (direct radiation is stronger than angled radiation).

Color gamuts and dynamic range

The preceding discussions conclude with an understanding of color gamut (the range of colors that can be seen or reproduced by an observer or a device) and dynamic range (the difference between the lightest portion of an image or field of view and the darkest portion).

When working with color desktop publishing, we should think of color gamut and dynamic range comparatively between the capabilities of human vision and those of the devices we use. In the end, humans will always be the standard for the success of one device or another to render an image, since the objective is to see the artwork or photograph that is reproduced through your system.

Human vision has the widest color gamut [image] that is, the range of visible color. It also has the widest dynamic range, capable of discerning gradation in shadow that is one millionth the brightness of the highlights in the field of view. Computer devices have a comparatively limited color gamut and dynamic range. Further, between types of devices there are different capabilities. For example, scanners and monitors have a much wider gamut and dynamic range than printers.

Taken together, color gamut and dynamic range define the color space in which we are sensitive to color, or in which a type of device operates. Different device types are associated with specific color spaces, and we can use color models to define these color spaces. A color space can also refer to the set of colors available in a color matching system. For each of their respective color systems, DIC, DuPont®, FOCOLTONE®, PANTONE®, TOYO, and TRUMATCH® have defined specific colors which you can choose from swatch books. With the exception of PANTONE® Spot Colors, these color matching systems are associated with color models. DIC and TOYO are based on both process colors and custom inks.

Click here [image] to read more about color models.

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Color models define color mathematically

Color models are mathematical representations of a color space. They provide a standard against which we can measure color, and a system through which mechanical devices can reproduce color.

Models tend to be based on three primaries, which corresponds to the tristimulus base of human vision. Each primary in the model is assigned a value within a specific range, and the combination of values determines the color. This is similar to the exercise we did as children, in which we mixed the pigment primaries of blue, red, and yellow to form what we called secondary and tertiary colors.

Even though models express color numerically, they are imperfect since color is affected by our perception. However, color models can be used in computer applications to define color output. If we send a color signal R255G000B255 to any monitor properly calibrated against a reference point, we will (in theory, anyway) always measure the same color (magenta, in this case).

CIE perceptual models

Perceptual models are based on how we perceive color. The most well-known models are those developed by the Commission internationale de l’eclairage (CIE). CIE XYZ was developed in 1931 as a mathematical model of how humans perceive color, and defines a standard illuminant, observer, and object. The model has the following characteristics:

There are a number of standard illuminants. The most common is Standard Illuminant D65, which has a spectral power distribution similar to average daylight with a color temperature of 6,500K.

The standard observer is defined through measurements based on the perceptions of a number of individuals with normal color vision.

The standard object is defined by a viewing angle (2- and 10-degree viewing angles) over a specified distance. The viewing angle determines the size of the object, and should not be confused with the angle at which the object is viewed.

The model incorporates three imaginary primaries to define color: the X, Y, and Z tristimulus values. These values do not correspond very well to perceived color, and are redefined as a set of chromaticity coordinates which are derived mathematically from X, Y, and Z. These new coordinates are x, y, and Y, where x and y define chromaticity and Y defines lightness.

When defining a color in CIE XYZ, we quantify the XYZ primaries, the standard illuminant, and the viewing angle. For example 21.21 13.37 9.32 D65 2-degrees means X=21.21, Y=13.37, and Z=9.32 under standard illuminant D65 with a 2-degree viewing angle to define size.

This model is important in that it was the first to let us describe color numerically without reference to a particular device (device independent). The problem with it is that it does not represent color in a perceptually uniform way and it’s not very intuitive to use. CIE L*u*v* and CIE L*a*b* are variants that were developed later to accommodate perceptual uniformity and ease of use.

CIE is used extensively in industrial applications, such as paint, plastics, and textiles. It is also used as a standard in broadcasting.

Additive and subtractive models

In an additive model, light is used to create color. The term "additive" is used to describe the radiant nature of light [image] that is, as we add light, color intensity increases. Another way to describe this effect is to say that the light source adds to the light captured on the retina. When all primaries are at full intensity, you get white [image] which is characteristic of the light primaries.

RGB is an additive model, in which the red, green, and blue components correspond to the light primaries. It defines the natural color space for monitors and scanners. In monitors, for example, each of the electron guns are associated with one of the components.

In a subtractive model, pigment or other colorants are used to create color. The term "subtractive" is used to describe the reflective nature of pigments - that is, as we add pigment, the light intensity decreases. Another way to describe this effect is to say that pigments subtract from the light reflected to and captured on the retina (since more light is absorbed by the pigment, resulting in less light reflected to the retina). When all primaries are at full intensity, you get a color that is close to black (true black is not possible in some subtractive color models).

Subtractive models include CMY and CMYK. These models are the natural color space of most printers, and are also the basis for most process color printing. Observe that these models correspond to the printer and pigment primaries.

HSB and HLS

HSB (hue, saturation, brightness) is a variation of RGB and is also based on the light primaries. Of all color models in use today, HSB most closely represents the way in which we perceive color. It presents an intuitive method of defining color.

Hue defines the actual color (red, yellow, etc.) in much the same way that you often see colors around the periphery of a color wheel.

Saturation defines the purity of the color. As you move across the color wheel (as opposed to around), you are removing a percentage of the color you are moving away from and adding a percentage of the color you are moving toward. As you move toward the center of the wheel, the color becomes increasingly gray due to equal percentages of the light primaries.

Brightness defines the amount of lightness in the color on a vertical scale (lightness can also be equated with the amount of white in the color). The brightness component is non-linear, which closely approximates how we see light and dark colors. As you move down the scale toward the dark area, the physical distance covered decreases for the same numerical value change.

HLS (hue, lightness, saturation) is a variant of HSB. The hue and saturation components are the same. The difference lies in the lightness component, which is a linear scale of color lightness to darkness.

Other color models

Other models include the following:

grayscale

YCC

YIQ

Click here [image] to read about how color models can help calibrate computer devices.

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YCC is the Kodak standard for digital photography and is the foundation for Kodak PhotoCD. YCC is a compression strategy for reducing the file size for high-resolution images. The image is split into a luminance component (grayscale - where the luminance component produces a complete grayscale image) and chrominance components (hue - which adds the color component). These parameters are similar to the YIQ model for broadcasting standards.


Computer devices reproduce color inconsistently

Your desktop system typically includes a scanner, a monitor, and one or more printers. In some cases, it can also include less common devices such as video cameras and digital still-photography cameras.

These devices do not reproduce color consistently from one to the next. For example, monitors from different manufacturers will produce different colors for the same digital color data. Even two monitors of the same model will reproduce different colors for the same color data.

This inherent inconsistency is critical in drawing and image retouching applications. Colors reproduced on one device in your desktop system are different when reproduced on another device. For example, the RGB blue on the monitor looks different when you send it to the printer, which reproduces a color more like violet. The problem is that what you thought you designed is not what came out in the end. Which device do you adjust: the scanner, the monitor, or the printer. And how should you adjust it?

Devices need to be calibrated, but that’s not where it ends

Manufacturers provide specifications that tell us that a device will reproduce color within specified tolerances. This means that you can line up several monitors and calibrate them to produce the same color given the same color data. There are a variety of calibration meters that you can use to do this:

Colorimeters: measures tristimulus values with a response similar to the human eye. Used in monitor calibration. The term "colorimeter" is also used to indicate a range of meter types that are used to measure color.

Spectrophotometer: measures spectral reflectance or transmittance of an object. Used for both monitor and printer calibration.

Densitometer: measures the opacity of a translucent colorant. Used for printer calibration.

Monitor display calibrator (a colorimeter)

To calibrate a monitor, you adjust the gamma values for red, green, and blue, and the white point value. You can also adjust the chromaticity, but this is generally not required even for advanced calibration. You can use one of the meters listed above to measure the monitor’s output, using the monitor’s controls to affect changes to output.

To calibrate a three- or four-ink printer, you adjust the amount of ink transferred to the paper and the amount of gray component replacement or undercolor removal. This is done using software controls. You can measure a printed sample using the meters described above and make adjustments as required. Professionals in the print industry have a high level of experience in this area [image] enough to be able to eye-ball the test sample and make the correct adjustments based on that assessment alone.

There is relatively little to do when calibrating a scanner. Scanner calibration uses a target sheet of color swatches and a data reference file. You scan the target sheet to produce a TIFF file of the scanner’s output. Software then takes over, comparing the values in the TIFF file with the values in the data reference file. This output can then be compared to the reference values in the data file to produce a set of values that define the scanner’s spectral responsiveness relative to a reference point.

The devices are calibrated: now what?

After calibrating all of your devices to manufacturer standards, you still have a problem: the image displayed on a perfectly calibrated monitor looks different from the same image printed on a perfectly calibrated printer.

This is where color management helps.

Click here [image] for an introduction to color management.

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Why do we need color management?

With color management, we can set up a common reference color space through which we map the color gamut of one device to the color gamut of another device. In this way, we obtain a predicable color rendering on both devices. In practice, this means that the photograph we scan looks pretty close to the image displayed on the monitor, which looks pretty close to the proof from the printer.

We say pretty close, because an exact match is virtually impossible. The color gamut of one device may be much larger than the gamut of another device, as is the case with the monitor and the printer. Also, the ways in which devices reproduce color are fundamentally different. Monitors reproduce color in the RGB color space (an additive color model), while printers reproduce color in the CMY and CMYK color spaces (subtractive color models).

This section of help provides some basics on color management and the Color Manager, and includes topics on:

how color management works

the difference between color management systems and color matching systems

an overview of the Color Manager wizard

Need more information?

Click on any of the above points to jump to the topic, or click here [image] to start a structured walk-through of this section of help.

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Color management ensures consistent output across devices

To ensure consistent output across devices, a color management system needs three things:

a set of accurate profiles which we can use to properly calibrate devices

an algorithm to convert the colors in the color space of each device to the color space of any other device

a filter that will let us work with a predictable palette of colors and preview the finished product on screen

Profiles

There are two definitions to understand when discussing device profiles:

Characterization: to define the relationship between the device’s color space and a reference color space. Characterization is done by the device manufacturer; it is a design consideration inherent in the device.

Calibration: to adjust the device’s output to match the color space defined through characterization. Users usually perform their own calibration, which can be done through mechanical settings or through computer software.

To create a profile, the color management system uses an output sample from the device which it compares to a set of reference values. For example, a target sheet of color swatches is scanned to produce a set of values for each swatch. These values are compared to a set of values known to conform to the independent color space for that device. You can do these calculations yourself, but computer software is better suited to the task.

Gamut mapping

With calibration and characterization complete, the colors in the color space of one device must now be rendered in the color space of each of the other devices. This is gamut mapping, in which color equivalence between color spaces is determined.

In most instances, there is adequate correspondence; the CMYK color space used by your printer falls within the color space of your monitor (hence, anything that you can produce on your monitor is printable).

However, there will be instances where a color on one device does not have an equivalence in the color space of another device. In this case, the closest approximation must be calculated.

One way to achieve gamut mapping is to compress the color gamut of the larger color space. In this way, the relationships between tones are preserved. Another way is to map out-of-gamut colors (from the perspective of the destination device) to the closest color available. This method preserves both color saturation and the consistency of the memory colors.

Color correction

From within the application, color correction adjusts color reproduction on the monitor to simulate how the drawing or image will look when printed. The filter uses the gamut mapping method selected through the color management system. Color correction re-enforces the WYSIWYG characteristics of your system while you are working on the drawing or image, and lets you do a considerable amount of proofing on screen.

Click here [image] for comparison of color management systems and color matching systems.

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Color management systems are different from color matching systems

Because we perceive color differently, and because computer devices render color imperfectly, we use both color matching systems and color management systems. Both systems help us smooth out differences and imperfections, but they are different.

Color matching system

A color matching system is a color chart. The manufacturing of the chart is carefully controlled to minimize variations, from pigment matching to the use of specific paper stocks. In addition to the color chart (which you would use as an office reference), you also have color swatches that clip out and attach to the artwork, giving the customer and the printer a specific description of the intended color by example.

The most widely used color matching systems for commercial printing are included

DIC Color Guides

FOCOLTONE® Color System

PANTONE® Spot Color

PANTONE® Process Color

TOYO 88 Color Finder system

TRUMATCH® Process Color System

Corel has also included the DuPont® Spectramaster® Solid Color Library for industrial coatings and colorants.

A color matching system is a visual reference point: you visually choose a color for the artwork, and you visually match the printed color to the swatch taken from the chart. It lets us say, "I want that color, you’ll get this color, and we printed this other color."

Color management system

A color management system is used to map the color information from the color space of one device to that of another device. This is also referred to as gamut mapping.

We can think of color management as "monitor centered". While we are limited in output characteristics of a particular printer, we can adjust how the drawing or image is displayed so that we can preview the finished product. (We assume that the printer we use, whether a desktop printer or a service provider, satisfies our printing needs.) In this sense, color management is monitor-based, since the visual representation afforded by the monitor is our interface to the capabilities of the desktop or pre-press system as a whole.

The characteristics of the drawing or image displayed on the monitor is a close approximation of the drawing or image that you will print. Remember that you are comparing the output of a radiant device to a reflective medium.

Click here [image] for an overview of the Color Manager wizard.

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Corel's Color Manager: a wizard guides you through
Corel’s Color Manager: a wizard guides you through

Corel offers a wizard to guide you through the Color Manager so that you can choose or create device profiles for scanners, monitors, and printers. The wizard uses these device profiles to build the system profile.

The wizard accommodates any level of fine tuning that you wish to undertake:

you can use pre-packaged device profiles to quickly set up a system profile (recommended for users with little or no experience in device calibration and gamut mapping)

you can create custom device profiles for an optimized system profile to compensate for variations in office environment, equipment aging, or operating conditions (recommended for experienced users who need to optimize for each stage of pre-press)

The wizard is presented so that you can create new system profiles or edit existing ones. When you create a new system profile, you can choose from a set of pre-packaged device profiles or you can create custom device profiles. When you edit an existing system profile, you can substitute the profile of one device for that of another, or fine tune by creating a custom profile. The wizard also lets you quickly bypass the dialogs for device profiles that you are happy with so that you can focus on the profile for a specific device.

You can invoke the wizard in any of the following ways:

an application icon in the Corel application group

from the tools menu

What the wizard needs from you

Before using the wizard, adjust ambient lighting to a comfortable level. Then, calibrate your monitor to the specifications defined by the manufacturer. Monitors vary in the number of features available: older monitors have only brightness and contrast controls, while some of the newer models have hardware controls for gamma and white point.

Monitor white point deserves particular attention. You may want to set the white point to match paper white, or you may want to set it to match the ambient lighting under which you view printed proofs. The hardware setting and the Color Manager setting must be the same. Always adjust your hardware before using the Color Manager.

There are also a few things the wizard is going to need from you. You can obtain these items either prior to starting the wizard or while you working with it.

A target sheet that you have scanned (stored in a TIFF file), and a data reference file for that target. These items are used for scanner calibration. If you are using the target supplied by Corel, the data reference file is already on disk. If you are using a third-party target, the data reference file is either provided on a floppy disk or downloaded from the manufacturer’s BBS. You will need to store this file on one of your local disk drives.

Monitor specifications for chromaticity and white point. These specifications are needed to adjust hardware settings and to set software controls if your monitor is not in the list of pre-packaged profiles.

Monitor calibrator. This is an optional item that you use to fine tune monitor calibration for gamma and white point (manufacturer specifications are not required). You must still complete hardware settings before using the Color Manager.

A color measurement file based on a target sheet printed from your printer. Creating this file can be time consuming, since you will be measuring hundreds of color samples and typing the values into a measurements file.

Click here [image] for information on working with Color Manager profiles.

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Working with Color Manager profiles

Working with device and system profiles is a straight forward process. If you’re a new user, you can choose from a set of pre-packaged device profiles; if you’re an experienced user, you can create custom device profiles to optimize your desktop publishing system.

Corel provides a wizard that walks you through the process of choosing or creating each of the following:

system profile

scanner profile

monitor profile

printer profile

When you have finished with the device profiles, the Color Manager automatically creates the system profile.

If any component of your system changes later, you must make this change known to the Color Manager by updating your system profile. Similarly, if you have access to multiple devices, you will need to build a System Profile for each combination of devices that you use.

Once the color management system has been set up for your device configuration, choose Color Correction under the View menu to adjust the color display to approximate the final output on your printer.

Need more information?

Click on any of the above points to jump to the topic, or click here [image] to start a structured walk-through of this section of help.

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Choosing a system profile

This dialog box lets you choose a system profile for the Corel Color Manager. You come to this dialog box either through Color Manager, Select Color Profile under the Tools menu or through the Color Manager Wizard.

You choose a system profile through the Select Color Profile menu selection after you have defined two or more profiles and you want to choose one for a specific purpose. This is a very quick way of changing profiles.

On the other hand, you typically choose a system profile through the Color Manager Wizard when you want to edit an existing profile. You can also use the Color Manager Wizard to choose from your library of profiles.

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The objective is to create a system profile

The purpose of the Color Manager is to map the color gamuts of all the devices used in your desktop PC to produce consistent color output across those devices. Device profiles are the building blocks used in the system profile: you calibrate your equipment to create device profiles, and the Color Manager uses these device profiles to derive the system profile.

You are asked for profiles for a scanner, a monitor, and a printer. If your computer system incorporates all three, then you’ll need profiles for each. If you are missing one of these devices (usually the scanner), then you can skip the dialog boxes for that device.

In most cases, Corel has already created a pre-packaged profile for each of the devices that you are using, and you simply choose the manufacturer and model number from the lists provided. The Color Manager then creates the system profile. With the system profile in place, the colors displayed on screen are consistent with what the printer produces.

If your project needs are more exacting, you will have to modify these profiles from time to time, since devices need to be recalibrated to compensate for operating and environment variations. At this point, you move into the more advanced areas of creating custom device profiles.

If one or more devices in the desktop system are not in the list of profiles that Corel provides, you can obtain additional profiles from Corel either directly or through CompuServe. If you still cannot obtain a profile for your devices, you can create new device profiles from scratch, based on either a set of generic default values or on the values in an existing device profile.

Over the months, you will want to fine tune the device profiles that you are using to compensate for changes in environmental or operating conditions. Or you may want to adjust a device to produce different effects (for example, to change how much black a CMYK printer uses). You can save these new device profiles and use them to create new system profiles.

You can develop as many system profiles as you need. For example, the series of profiles that you create may correspond to a set of devices recalibrated over time, or to different combinations of devices that you use for different projects. You identify your system profiles through a descriptive name, and you can also add descriptive text. When you start the Color Manager, you always see a list of the system profiles that you have on hand [image] complete with a list of the component device profiles and any descriptive text that you entered.

Click here [image] for information on creating a scanner profile.

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First, create a scanner profile

Choosing or creating a scanner profile is the first step in setting up the color management system. A scanner profile is needed so that the Color Manager can measure the variance between the scanner’s output and a known reference point. This is essentially software calibration of the device to a standard.

Using pre-packaged scanner profiles

In most cases, Corel has already profiled your scanner and you choose the manufacturer and model from the lists provided. If your scanner is not on the list, you can choose Other to custom calibrate or None to skip scanner calibration.

These pre-packaged profiles are most useful when the scanner is new and not subject to the effects of age on its light-receptive components. Also, if you are not comfortable working with custom scanner calibration, you will appreciate the ease of using pre-packaged profiles in setting up color management. You can use these profiles and obtain satisfactory results in all situations.

Creating custom scanner profiles

Since the scanner’s light detectors are affected by prolonged use, the RGB output signals will vary. Age usually affects color balance and linearity; the chromaticity component is relatively stable. This means that a new profile is periodically needed for the scanner, since the RGB outputs vary from month to month (depending on frequency of use) and the pre-packaged profile is no longer as accurate as it can be.

To create a custom scanner profile, there is little more that you need do other than scan a target sheet. Here are the basic steps that you follow:

Scan a target sheet (you can use either the Corel target or a third-party target).

Type the name of the TIFF for the scanned target.

Type the name of the data reference file (for third-party targets only [image] the Color Manager knows the location of the data reference file for the Corel target).

Set the alignment cross-hairs when the target is displayed on screen (this ensures that the Color Manager captures the correct values when building the device profile).

The digital output of the scan is then compared to a data reference file, and the scanner profile is derived from that comparison. For both the TIFF and the data reference file, you can type in a file name (and a path, if necessary) or you can use the Browse button to locate the file through the Windows file manager dialog.

When you create a custom profile, the Color Manager asks for a manufacturer name and a model number. Enter this information accurately, since the Color Manager organizes scanner models by manufacturer and shows manufacturers alphabetically in the drop-down list. If the model name for a manufacturer is already in use, the Color Manager tells you so and requests a different name.

Click here [image] for information on creating a monitor profile.

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To align the scanned target
Aligning the scanned target

When you calibrate the scanner and the printer, you must correctly align the contents of the scanned target file. This is necessary to ensure that the Color Manager correctly reads the values in the target file.

Alignment involves lining up the corners of the outline with the cross-hairs on the image. You can do this by dragging the corner of the outline and "eye-balling" the alignment. Or, you can use the Zoom Tool as described in the following procedure.

To align the target image using the Zoom Tool

1.	Click the Zoom Tool.

2.	Click a corner of the target to enlarge. The cursor turns into a cross-hair.

3.	Align the cursor cross-hair with the corner cross-hair in the image and click.

4.	Repeat this for all corners.

5.	Click Next when you’re done to generate the profile.

Note

If you scanned the target in a different orientation, use the left and right Rotate Tools to orient the target right-side up.

If you scanned the target in a different orientation, use the left and right Rotate Tools to orient the target right-side up.

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Second, create a monitor profile

Choosing or creating a monitor profile is the second step in setting up color management for your desktop system. An accurate monitor profile ensures that when you use color correction, what you see on screen is what you reproduce on the printer. As with the scanner, a monitor profile is essentially a means of calibrating device output through software. Monitors also have a second set of variables related to environmental conditions. Characteristics of the ambient lighting in which the monitor is viewed and the temperature of the light in which proofs are viewed will influence how you set up your monitor.

Preparing to create a monitor profile

Before creating the profile, do the following:

Leave the monitor on for an hour or so. This warms up the electron guns to a stable temperature, since color output varies depending on how warm the guns are.

If the monitor has mechanical adjustment controls, ensure that they have been calibrated to the manufacturer’s recommended settings. Adjust the temperature to match the light in which printed proofs are viewed.

Adjust the brightness to match the ambient lighting in the room (brighter ambient lighting decreases the monitor’s color gamut). Do this after the monitor warms up.

Using pre-packaged monitor profiles

As with the scanner profile, Corel has probably already profiled your monitor and you choose the manufacturer and model number from the lists provided. (If your monitor is not on the list, you can choose Other to custom calibrate or None to skip monitor calibration.)

These pre-packaged profiles are most useful when the monitor is new and not subject to the effects of age on its electron guns. If you are not comfortable working with custom monitor calibration, you will appreciate the ease of using pre-packaged profiles in setting up color management. You can use these profiles to obtain satisfactory results in all situations. After that, the most you need to do is take care that environmental conditions remain stable, and that the monitor is warmed up before use.

Creating custom monitor profiles

Since monitors age, the RGB output signals will vary. This means that a new profile is periodically needed, since the RGB outputs vary slightly from month to month and the pre-packaged profile is no longer as accurate as it can be. Depending on your project requirements, you may want to create a custom profile to compensate for any of the following:

changes in ambient lighting conditions throughout the day or evening

monitor age (variations in the output of electron guns)

different temperature for the ambient lighting under which printed proofs are viewed

To create a custom monitor profile, you need to set the monitor’s white point, chromaticity, and gamma. You can do this by sight, comparing output to a target photograph provided by Corel, or you can use measurement devices such as a colorimeter or a spectrophotometer.

During monitor calibration, you can review the effects of your selections by clicking the Preview button; you can also return all values to the defaults by clicking the Reset button.

When you create a custom monitor profile, the Color Manager asks for a manufacturer name and a model number. Enter this information accurately, since the Color Manager organizes models by manufacturer and shows manufacturers alphabetically in the list. If the model name for a manufacturer is already in use, the Color Manager tells you so and requests a different name.

Click here [image] for information on creating a printer profile.

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Choosing your initial values for monitor calibration

When you calibrate your monitor, you base the initial values on either a default set (defined by the Color Manager Wizard) or the set of values from an existing monitor profile. These values are loaded into the interactive monitor calibration dialog box, through which you make the necessary adjustments.

If you want to use the default values, the Color Manager proceeds to create the device profile for interactive calibration. If you want to use the values from an existing device profile, you must select the manufacturer and model from a list.

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Lastly, create a printer profile

Choosing or creating a printer profile is the final step in setting up color management for your desktop system. A printer profile is a means of calibrating output through software. Like scanners, printers are not subject to environmental conditions.

Using pre-packaged printer profiles

As with the scanner and monitor profiles, Corel has probably already developed a profile for your printer and you choose the manufacturer and model number from the lists provided. (If your printer is not on the list, you can choose Other to custom calibrate or None to skip printer calibration.)

These pre-packaged profiles are most accurate when the printer’s colorant systems are fresh and the transfer mechanisms are optimized. If you are not comfortable working with custom calibration, you will appreciate the ease of using pre-packaged profiles in setting up color management. You can use these profiles to obtain satisfactory results in all situations. After that, the most you need to do is take care that printer colorant is sufficient and fresh, and that the printer’s transfer mechanisms are maintained at a reasonable level of cleanliness and performance.

When you select a printer from the device library, you have the choice of using the printer profile as is, or editing the profile for K-curve (gray component removal) and total area coverage (TAC). You can select from a range of presets for the K-curve.

Creating custom printer profiles

As the printer is used, output will vary as colorant is used up, colorants vary slightly in their purity, and the transfer mechanisms will require maintenance. This means that to have a well-calibrated system, an updated printer profile is periodically needed since the printer’s mechanical state changes over time.

Creating a custom printer profile can be rather involved, depending on the method you use. The simpler way is the scanner method, in which you print the target file provided by Corel and scan it through the calibrated scanner in your system; this completes the measurements file for you. The more time-consuming (and more accurate) method is the file method, in which you print the target sheet and measure each color swatch with a spectrophotometer and type the results into a measurements file. Once the measurements file is complete (either through the scanner or manually), you adjust the TAC and K-curve.

When you create a custom profile, the Color Manager asks for a manufacturer name and a model number. Enter this information accurately, since the Color Manager organizes scanner models by manufacturer and shows manufacturers alphabetically in the list. If the model name for a manufacturer is already in use, the Color Manager tells you so and requests a different name.

Using printers with built-in color management

If your printer has a built-in color management circuit, you must disable it before using the Color Manager.

These printers expect to receive color information as RGB data, which the built-in color management circuit converts to CMY or CMYK (depending on the color model used to map to the printer’s color space). Color management sends CMYK data to the printer for calibration, which presents a conflict at the printer. Because of this, the Color Manager will not work correctly.

To disable color management at the printer, contact the manufacturer or refer to the printer documentation.

Click here [image] for information on organizing device and system profiles into libraires.

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Choosing your initial values for printer calibration

When you calibrate your printer, you base the initial values on either a default set (defined by the Color Manager Wizard) or the set of values from an existing printer profile. These values are used as the initial values for K-curve and total area coverage (TAC).

If you want to use the default values, the Color Manager Wizard proceeds to collect information from you on the source of your printer calibration. If you want to use the values from an existing device profile, you must select the printer manufacturer and model from a list.

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Printing the test pattern file

When you calibrate the printer using a colorimeter, you need to print a test pattern. The test pattern contains numbered color swatches which you will measure using a CIE XYZ colorimeter. You then record the measured values in an ASCII file.

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You can use the wizard to manage profile libraires
You can use the wizard to manage profile libraries

As you work with the Color Manager, you may end up creating a number of different system and device profiles. Less experienced users will probably create a set of system profiles based on the pre-packaged device profiles (assuming that there is a variety of device configurations to support). More experienced users will probably develop a set of device and system profiles to compensate for different environments, the same environment at different times of day, aging equipment, and different device configurations. It depends on how exacting your project requirements are.

Regardless of the number of profiles you create, the Color Manager organizes them in a simple fashion:

System profiles are listed alphabetically. When a profile is highlighted, the component device profiles are displayed.

Device profiles are organized alphabetically by manufacturer.

For each device manufacturer, profiles for models are organized alphabetically by name and number

Through the dialog boxes in the Color Manager, you can remove any of the system and device profiles from the library.

Removing system profiles from the library

This first dialog box of the Color Manager wizard lets you delete any of the system profiles, except for the default profile. Click the system profile, then click on the Remove button.

Only the system profile is removed from the library; device profiles remain intact. This feature lets you use the device profiles to create other system profiles. If you remove the system profile that your applications are using, the Color Manager defaults to the _default.ccm profile (the _default.ccm file cannot be deleted).

Removing device profiles from the library

Whenever a dialog box lets you choose device profiles from a list, you can remove one or more profiles from the library. To do this, click the device profile, then click on the Remove button.

If the device profile is used in a system profile, you can still remove it since the device-specific information is incorporated into the system profile and is not lost. When you choose that system profile again and want to edit profile information for the removed device, it will recreate the deleted device profile.

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Additional notes on Corel’s Color Manager


Gamut mapping

Gamut mapping is a function of the Color Manager through which the colors available on one device are mapped to the color space of the destination device. Through the Color Manager, gamut mapping is done for scanner output, monitor display, and printing.

The Color Manager offers two gamut mapping techniques: photographic and saturation.

Photographic mapping uses a gamut compression technique to fit the entire source gamut within the destination gamut. The color range in the source gamut is shifted toward the neutral axis in the destination gamut (compressed). The advantage of this technique is that the relationship between colors is maintained. The disadvantage is that all colors are shifted which may, in some cases, affect critical colors such as the memory colors. This gamut mapping technique is best suited to printing photographs and illustrations with continuous tone.

Saturation mapping expands or contracts the source gamut to fit the destination gamut. The maximum saturation available on the printer can be achieved without changing the hue. This technique is useful for printing in business applications and when you are reproducing on devices that dither images (the dithering pattern may be made less visible).

You can choose either gamut mapping technique. Use photographic mapping if you work in Corel PHOTO-PAINT; use saturation if you work in Corel DRAW. Alternately, if you work in both PHOTO-PAINT and DRAW, you can choose the Automatch option. With this option, the application determines whether it is printing a vector or a bitmapped object and applies the appropriate mapping technique.

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TIFF and reference files for scanner profiles

A TIFF (tag image file format) file is encoded in a standard format for photographic images, and is a standard output format for desktop and high-end scanners. The TIFF file that the Color Manager uses in scanner calibration is a scanned target sheet of 500 or so color swatches that are set up in a specific sequence.

A data reference file is a TIFF file that represents the target sheet, but its values are not associated with the output of any particular scanner. Its values are an objective measurement of the swatches on the target sheet, created by measuring each swatch with a colorimeter.

The scanner profile is derived by comparing the scanner’s output with the values in the data reference file. The Color Manager uses the difference in values to determine how the scanner’s output must be modified before mapping to the device-independent color space. The sample represented by the target sheet is sufficient to map all colors from the source color space to the target color space.

You can use either the target supplied by Corel or a target and data reference file supplied by a third party. You can scan the target before starting the wizard if you like, but the Color Manager also provides a facility for scanning the target while inside the wizard.

If you use the target supplied by Corel, the data reference file is already on your hard disk and the Color Manager automatically accesses it. If you use a third-party target, you must supply the Color Manager with the location of the data reference file that is shipped with the target. You can leave the target on the floppy disk it was distributed on, since there is a browse facility that you can use to access files anywhere on your computer.

The target sheet is key to the accuracy of scanner characterization. Do not leave the sheet out in the light where it is subject to fading; a faded target will not match the reference points defined in the data reference file. If you use the target sheet frequently, periodically contact the manufacturer for a replacement. It is best to obtain a complete package that includes both the target sheet and the data reference file, since the values in the file may change from release to release.

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Interactive monitor calibration: adjusting chromaticity, gamma, and white point

Interactive monitor calibration lets you change values for chromaticity, gamma, and white point, and then preview the new values on a photograph.

This is a fairly complex dialog box, with a number of controls that deserve further explanation. During monitor calibration, you can return all values in the dialog box to the default values by clicking the Reset button. To preview your settings, click the Preview button; you can compare the results to the target photograph included in with the application.

Chromaticity

Chromaticity corresponds to the monitor’s color gamut (the number of saturated colors that the monitor is capable of reproducing). Chromaticity values are stable and almost identical between monitors, and they usually do not need to be adjusted. The default values provided by the Color Manager are sufficient. If you do want to change these values, you can change them through one of two controls:

the visual selector, by dragging the marker to the correct area

numeric entries for x and y, by clicking on the number box and typing the new value

Click the radio button for the primary color that you want to change. Changes made through one control are immediately reflected in the other controls for that color. Chromaticity changes are difficult to evaluate using the Preview button.

There is also a list of pre-packaged settings in the Phosphors list box. Click on the Ambient light drop-down list to choose a setting for environmental lighting.

Gamma

Gamma controls the monitor’s brightness. Although brightness can be adjusted individually for each color, an average value is often used.

Click the radio button for the primary color that you want to change. You can change the gamma setting using either one of two controls:

the slider next to the gamma display box

the number box under the radio button

Changes made in one control are immediately reflected in the other. Use the Identical RGB value radio button to adjust gamma for all colors to the current color. When viewing the gamma adjustment, sit approximately four feet back from the monitor.

Before using the interactive calibration dialog box, you must adjust the monitor’s hardware settings for gamma to match the software settings that you will make through the Color Manager. On most monitors, you use the brightness controls to complete hardware adjustment. Some monitors have a specific control for gamma, either a single control for average gamma or a separate control for each of red, green, and blue.

Monitor white point

White point is the measure of the light produced by the monitor when all electron guns are set to full intensity. White point is defined through its corresponding temperature measured in degrees Kelvin (K). Most monitors have a white point of 8,000K to 9,000K.

You have some choices when adjusting white point. You can adjust to match the paper white on which proofs are reproduced, which is around 5,000K, or you can adjust to match the ambient lighting under which proofs are viewed, which is around 4,700K. Reducing the white point also reduces the monitor’s dynamic range, since the electron guns cannot fire at maximum intensity after the adjustment has been made.

To start white point calibration, click the Monitor white point radio button. You can change the white point setting though either one of two controls:

the scroll bar below the white point display box

the number box to the right of the slider

Changes made in one control are immediately reflected in the other.

Click the drop-down list to choose from a list of white point presets. Choose Custom to set white point using x and y coordinates (based on the CIE xyY coordinates, which some monitor manufacturers use to define white point).

Before using the interactive calibration dialog box, you must adjust the monitor’s hardware settings for white point to match the software settings that you will make through the Color Manager. On most monitors, you use the brightness and contrast controls to complete hardware adjustment. Some monitors have a specific control for white point (also called color temperature).

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Building a printer output measurement file

To build the printer device profile, you need to print a target sheet and measure the color swatches. The Color Manager compares the measurements you take against the reference values for the target sheet to derive the adjustments that must be made when printing.

The quickest way to create the measurement file is to scan it on a calibrated scanner to create a TIFF file. The Color Manager compares the values in the TIFF file with the values in a measurement file.

The most exacting method is to print a target sheet and measure each swatch with a spectrophotometer. You then enter the measurements into an ASCII file using a text editor. Your entries into the measurements file should follow these guidelines:

Begin measurements of each swatch in the numerical order printed on the target sheet.

Each line in the file contains measurements for one swatch only.

Do not include the swatch number in the measurement file.

Measurements are in CIE XYZ100 format, where values for X, Y, and Z are in the range 0.0 to 100.0.

Values for X, Y, and Z can have up to 28 decimal places.

Each value in a line must be separated by at least one space (but can have as many spaces as you like).

The following is an example of a measurements file, with X, Y, and Z values to 2 decimal places.

15.64 16.23 11.83

 5.50  5.31  2.72

 5.55  5.05  1.46

 6.67  5.99  1.26

 7.62  6.69  1.09

25.88 25.58 12.11

14.82 15.63 11.43

 4.88  5.22  2.51

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Adjusting printer TAC and K-curve

Total area coverage (TAC) and the K-curve can be used to control both the amount of ink put on the paper and the quality of the colors produced. While the essentials of the printer profile are derived using the measurement and reference files, TAC and K-curve are used to fine tune printer output to produce a desired result.

How TAC and K-curve settings affect the final output are described in the following paragraphs. However, when setting TAC and K-curve, testing and experience are the best guides. Print a sample that you can easily evaluate against a reference point (a photograph, original drawing, or target sheet), and adjust the values as needed. You may have to do this several times, or only once, depending on your level of experience.

Setting TAC percentage

TAC defines the amount of ink put on the paper. If you have full saturation of each of cyan, magenta, yellow, and black, you end up with 400% coverage (100% of each ink). In almost all cases, this level of coverage is impossible to apply with satisfactory results. Most printers support a practical maximum of 300% coverage, with an optimal TAC setting from 260% to 280%. The practical maximum TAC depends on the speed of the printer and the technology on which the printer is based. Refer to the technical documentation that comes with your printer for the best setting, or contact the printer manufacturer.

TAC is primarily used for calibrating four-ink printers. TAC can be adjusted for three-ink printers, but is generally not required since the theoretical maximum of ink on the paper is 300%; however, you may want to adjust the TAC setting downward a bit and test the results.

TAC can be adjusted to values between 200% and 400%. Higher TAC values result in steeper curves on the CMYK Plates graph.

Setting the K-curve

The K-curve represents the amount of gray component replacement (GCR) used at print time, and is used for four-ink printers only. A steeper curve means increased GCR in the shadows. The changes generally have these effects:

A shallow K-curve results in blacks achieved using more C, M, and Y inks; the black has a warm and glossy character.

A deep K-curve results in a darker, truer black (less warmth and gloss).

GCR is a variation on undercolor removal. In any color, whenever there is a value for cyan, magenta, and yellow, we can say that there is a gray component that can be replaced with black. This approach to printing has four advantages:

it reduces the amount of ink put on the paper

it results in more consistent grays (since grays are now made up primarily of black ink)

it reduces variations in color (if ink coverage varies, colors become lighter or darker instead of changing hue)

it reduces costs (less of the more expensive colored inks are used)

The drawback is that darker colors have reduced color density, and it is more difficult to adjust inks for color balance.

Click on the Black colorant drop-down list to select from a list of K-curve presets.

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A word for the new user

To get you started, Corel has simplified color management so that you can get up and running quickly. Device profiles are available for most common brands of scanners, monitors, and printers used in desktop publishing, and the Color Manager wizard greatly simplifies the process of profile selection.

The following steps provide an overview of the process you follow through the Color Manager wizard.

Start the wizard.

Click Create a new system profile and type a file name.

Click Automatch as your gamut mapping technique.

Choose your scanner manufacturer and model from the list (or choose None if you don’t have a scanner).

Choose your monitor manufacturer and model from the list.

Choose your printer manufacturer and model from the list (or choose None if you don’t have a printer).

If one or more of your devices are not in the list, or if your project requirements become more demanding, you will have to fine tune your color management system profiles so that whatever you scan, draw, and print is more accurately rendered on the monitor. You do this to correct drift in the output capabilities of each device and to correct for changes in your production environment.

As this point, you are ready to use the manual calibration features in the Color Manager wizard. When using these features, press F1 at any time for online help.

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Using the device profile list dialogs
Using the device profile list dialog boxes

Corel has developed profiles for most commonly used devices. The devices in your system have likely been profiled and are included in the list.

The list is organized by manufacture which you can choose on the left side of the dialog box. For each manufacturer, the model names and numbers are listed, which you can choose from the right side of the dialog box.

Initially, you may want to use the packaged profiles that correspond to the devices you are using. This approach will quickly and easily give you good color management across the system.

Over the months, as you fine tune the system profile by creating custom device profiles, you can place new device profiles under the manufacturer by model name and number plus a unique code that distinguishes the profile as a refinement. This approach ensures that the model and refinement appear under the correct manufacturer.

You can develop numerous refinements, or you can continuously refine a single system profile as your needs evolve. Fine tuning over time ensures that color management in your system is optimized for the applications you use, the unique characteristics and age of your equipment, and your office environment.

Need an update to your profile list?

If a profile is not on the list for one or more of your devices, it may still be available. For a disk of updated profiles, contact Corel Corporation directly or through CompuServe.

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Three-ink and four-ink printers

The Color Manager can accommodate both three-ink and four-ink printers.

Most printers available today are four-ink; they print in cyan, magenta, yellow, and black. When printing in process color, these printers lay down colorant in the order of black, cyan, magenta, and yellow darkest to lightest or least transparent to most transparent. This gives the print job a glossy appearance since yellow is laid down last. When printing with black and one or more spot colors, these printers lay down black last. Some four-ink printers can be configured as three-ink printers, in which the black component is not available.

When your create the device profile for four-ink printers, the settings for Total Area Coverage and the K-curve (the amount of black used in the image for gray component replacement) are key to producing the highest quality printing possible. When building the device profile for three-ink printers, adjustments for TAC and K-curve are not required.

There are also RGB printers. These printers accept RGB input either at the software driver level (within the application) or at the printer level, and perform their own color management. These printers still reproduce color using CMY or CMYK. Since the Color Manager anticipates sending CMY or CMYK data to the printer, color management must be turned off at either the software driver level or at the printer. For more information, refer to the technical documentation for the printer or to the manufacturer.

Classifying your printer

If you are uncertain which type of printer you have, click Classify to print a test pattern. Read the instructions on the test pattern sheet.

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GRAYSCALE COLOR MODEL


Use grayscale to choose from 256 shades of gray. Each colors is defined as a single value between 0 and 255, where 0 is darkest (black) and 255 is lightest (white). A single visual selector is used. A grayscale value can also be thought of in terms of the other color models: in RGB, a grayscale value corresponds to equal amounts of all RGB colors; in CMYK, a grayscale value corresponds to zero C, M, and Y values with a positive K value; in HSB, a grayscale value corresponds to zero H and S values with a positive B value.


YIQ


YIQ is the color model used in television broadcast systems (North American video standard - NTSC). Colors are split into a luminance value (Y) and two chromaticity values (I and Q). On a color monitor, all three components are visible; on a monochrome monitor, only the Y component is visible. The square two-dimensional visual selector defines the I and Q values, and the vertical visual selector defines the Y value. All values are scaled from 0 to 255. In Corel PHOTO-PAINT, the Y component of the splitting process produces a grayscale image that is often superior to results obtained with a grayscale conversion using the Convert To command from the Image menu.


DIC PALETTES


Offers colors that are available through the DIC Color Guide, DIC Color Guide Part II, and DIC Traditional Colors of Japan. Colors in these palettes are created by mixing DIC brand inks. Reproduction through Corel applications is achieved through the CMYK color space. Colors can be displayed by name or swatch through the Color Options menu. Swatches are identified by palette and color ID code:

DIC id# for DIC Color Guide

DIC Part II id# for DIC Color Guide Part II

DIC Traditional id# for DIC Traditional Colors of Japan


DUPONT PALETTE


Offers colors that are available through the DuPont® Spectramaster® solid color library. This library was developed to provide a paint color selection and matching tool for industrial coatings and colorants. Colors are based on L*a*b* and are converted to RGB for display and CMYK for printing. Colors can be displayed by name or swatch through the Color Options menu.


FOCOLTONE PALETTE


Offers colors that are available through the FOCOLTONE® color system. Colors are based on CMYK, and therefore do not add additional color separation plates. Use the scroll bar on the right to display other areas of the palette. Colors can be displayed by name or swatch through the Color Options menu.


PANTONE SPOT COLORS PALETTE


Offers colors that are available through the PANTONE® Spot Colors (also known as PANTONE® Matching System). You define tint through the Tint Number Box, ranging from 0 (lightest) to 100 (darkest) to control saturation. You can also define PostScript options. Since spot colors correspond to solid inks and are not CMYK-based, each unique color applied to an object results in an additional color separation plate. In Corel DRAW, you can use spot colors freely. In PHOTO-PAINT, you can use spot colors only in CMYK images to affect duotones. Colors can be displayed by name or swatch through the Color Options menu. See also PANTONE® Process Color system.


PANTONE PROCESS COLOR PALETTE


Offers colors that are available through the PANTONE® Process Color system, which is based on the CMYK color model. The first 2,000 colors are two-color combinations; the remainder are three- and four-color combinations. Colors are based on CMYK, and therefore do not add additional color separation plates. Use the scroll bar on the right to display other areas of the palette. Colors can be displayed by name or swatch through the Color Options menu. See also PANTONE® Spot Colors.


TOYO PALETTE


Offers colors that are available through the TOYO 88 Color Finder system. The range of colors offered here includes those created using TOYO process inks and those that are reproduced using TOYO standard inks. These colors are defined using the L*a*b* color space and are converted to RGB for display and CMYK for printing. Colors can be displayed by name or swatch through the Color Options menu.


TRUMATCH PALETTE


Offers colors that are available through the TRUMATCH® color system. This system is based on the CMYK color model and therefore colors do not add additional color separation plates. Colors are organized by hue (red to violet), saturation (deep to pastel), and brightness (adding or removing black). Use the scroll bar on the right to display other areas of the palette. Colors can be displayed by name or swatch through the Color Options menu.