Saturday, January 10, 2009
Trying to achieve consistent color across multiple devices connected to your computer can still generate its share of head-scratching, hair-pulling, and, yes, even the odd expletive. The truth is, a completely flawless method of desktop color management doesn't yet exist, although some systems come close. If you're a CorelDRAW Graphics Suite 12 user tackling color management for the first time, or just curious about how it's supposed to work, you've come to the right place.
Why Should You Use Color Management?
To illustrate why color management is important to anyone working in color, let's look at a typical scenario that you may have encountered. You scan an image or take a digital picture, open it on your computer, and then print it from your desktop printer. At each step in the process, you notice slight differences in color. This means that the colors in your final printed output may not exactly match the original you scanned. Now that we've nailed the problem, how do you solve it?
The reason for the color difference is that each color-capable device connected to your computer has its own special way of recording, displaying, or reproducing the same color values. The colors your eyes see may not match those that your scanner or digital camera can capture, nor will they perfectly match what your monitor or desktop printer can reproduce.
Will you ever be able to match the original scanned image exactly? Unfortunately, the answer is a qualified "no." What you can do, though, is to try to achieve a reasonably close display facsimile. CorelDRAW Graphics Suite 12 lets you do just that.
Color management enables you to match colors between devices that use color profiles - descriptions that conform to standards set out by the International Color Consortium (ICC). The profiles are compared according to the internal RGB color space shared by CorelDRAW 12 and Corel PHOTO-PAINT 12, and the corrections that are fed back to your monitor are based on each device's capabilities. When you print an image, your monitor's profile is compared with the printer profile, and your monitor's colors are corrected to reflect what the printer will actually print. If the colors aren't right, your monitor will tell you.
These days, color profiles are often readily available. Newer color devices automatically copy profiles to your system during installation. Others are supplied on disc by the device manufacturer. Often, you can install color profiles automatically through your operating system, using Plug and Play technology, or you can obtain them online. If you need a specific ICC profile, the best place to look is the support area of the manufacturer's Web site. Here are a few popular sources:
Of all the color devices connected to your system, your monitor is by far the most important, so you need to be confident that what you're seeing is accurate. You'll get the best results by using a model capable of rendering precise, consistent, and accurate color. You'll also want to ensure that the ICC profile assigned to your monitor is accurately indicating the colors you assign. Without ensuring this accuracy, there's no guarantee that other devices will reproduce the colors you want. Also, the age of a monitor can significantly affect the color it shows. Monitor quality can degrade over time - especially if the monitor is of the cathode ray tube (CRT) variety. If your monitor has seen better days, the need for effective color management provides the perfect excuse for upgrading to a fresh model.
A Step-by-Step Approach for the Wary
The Color Management feature of CorelDRAW Graphics Suite 12 is much easier to use than in past versions, but it's still a full-featured tool. The main dialog serves two functions: it graphically illustrates the current color management setup, and it provides control over all options in a central location. You can access these options (shown below) from within either CorelDRAW 12 or Corel Photo-PAINT 12 by choosing Tools > Color Management.
Each of the graphic icons represents the color devices you can control. Click the profile type selectors below each graphic icon (shown below) to assign your device profiles. Click the arrows between the icons to control how display color is corrected. To access advanced options, click directly on the icons themselves.
Although the options might seem a little overwhelming when you first work with them, creating your own color management setup is relatively straightforward if you approach it one step at a time. The following provides a quick walk-through.
Step 1: Assign Your Device Profiles
Choosing a profile to a color device is a simple step, provided that your hardware appears in the selector list. If you don't see it listed, you can load a profile from disc or connect to Corel's server, which provides a list of profiles to download (as shown below). If the profile for a connected device isn't available, leave the selection set to its generic profile (the default) until you can obtain one. Just remember that choosing the correct monitor profile is the most critical step in the process.
Step 2: Turn Color Management On or Off
Turn color management on or off by clicking the arrows between the graphic icons for your color devices and your internal RGB color space. In the illustration below, each device is set to the active state. Turning the active state of a device off essentially disables its profile so that no color correction is applied. The arrow pointing to the Internal RGB profile from the Import/Export icon controls whether correction is applied to imported documents that have embedded ICC profiles. The arrow pointing in the opposite direction controls whether your current ICC profile is included with exported images - which is often the best route.
Step 3: Choose the Color Correction Method for Your Monitor
With your profiles assigned, you can choose which printer's capabilities your monitor will emulate by clicking the arrows that point from the printer icons to the monitor icon (shown below). Ideally, you'll choose the device that you will use to print the final result. Clicking either of the arrows automatically activates that printer's color profile. Only one printer's capabilities can be simulated at a time, so activating one printer's color profile turns off the other printer's color profile.
If the document you're proofing on your monitor is destined for final output to a separations printer, you can also set your selected composite printer to simulate the final color results. To activate this feature, click the arrow that sweeps along the bottom of the dialog and points from the separations printer icon on the right side to the composite printer icon on the left side.
Step 4: Save Your Settings
After you've gone through the effort of assigning profiles and setting preferences, it's worthwhile to save your setup using the color management Styles options. To save the entire arrangement, click the "+" button, and name your new style in the Save Color Management Style dialog (shown below).
By saving your setup, you can retrieve it from the styles list later and use it with other drawings. You can also use preset styles included with CorelDRAW Graphics Suite 12, which are optimized for certain operations, or you can quickly reset all profiles to defaults. Once a style is saved, it is embedded with your drawing. If you move a document between computers and open it in either CorelDRAW or Corel PHOTO-PAINT, you can extract the embedded styles by selecting the Extract Embedded ICC Profile option in the Open dialog (shown below).
Before the document is opened, the Save As ICC Profile File dialog opens, which lets you extract and store the file. By default, all profiles are stored in your .../Application Data/Corel/Graphics 12/User Color folder.
Tackling More Advanced Options Besides being able to set profiles and choose correction preferences, you can also use the Color Management dialog to choose more advanced settings for certain devices and operations. These settings are perhaps the most complex and critical of all the options you need to choose. To access them from the Color Management dialog, click directly on a specific graphic icon (Import/Export, Printer, Monitor, or Internal RGB). In the dialog that opens, you can set the following advanced options.
Advanced Import/Export Settings. Clicking directly on the Import/Export icon opens the dialog shown below. Here, you can specify whether you want to use the embedded ICC profiles contained in imported images, or whether your current profile is embedded into images you're exporting from your document. In either case, you can override the profiles converted or embedded by choosing to use your current Internal RGB profile or the profile for a specific device.
Advanced Printer Settings. Clicking the icon for either the composite printer or the separations printer opens the dialog shown below. You'll see a list of the currently installed printer drivers with options for overriding the profiles assigned in the color management setup.
Advanced Display Settings. Clicking the monitor icon opens the dialog shown below, which lets you control complex color correction properties of your monitor. While a printer simulation is selected, you can view colors that fall outside your printer's gamut, which is the range of colors your printer can reproduce.
Enabling the Highlight Display Colors Out of Printer Gamut option causes an alarm color to appear in the areas when a certain color specified in your document can be accurately reproduced by the selected printer (based on its color profile). The illustration below shows the effect of an out-of-gamut display, with green used as the alarm color.
You can click the Warning Color button to choose the alarm color, and you can use the Transparency slider to control how opaque the alarm color appears on-screen. For example, if your printer simulation is set to a CMYK separations printer, the gamut alarm will highlight any RGB colors.
Advanced Internal RGB Settings. Clicking the Internal RGB icon opens a settings dialog that lets you choose from a collection of rendering intent types (shown below). This dialog also lets you change color engines from the default Kodak Digital Science color-management module if an alternate is available. The rendering intent method you choose controls how your internal color space converts and displays out-of-gamut colors on your monitor.
Although the science behind color management may seem a little intimidating at first, the following explanations may help you decipher what is produced by each of the five types of rendering intents:
- Absolute Colorimetric. This method is useful if the gamut of the color proofing printer you're using is larger than the gamut of the final output printer you're attempting to simulate. It essentially preserves all in-gamut color, including the white point, which affects image highlights and contrast. This method maps out-of-gamut colors to the next closest hue by altering their saturation and lightness when displayed.
- Relative Colorimetric. If your drawing consists mostly of color vector objects, you might prefer this method. It's similar to the Absolute Colorimetric method, but it also alters the white point of the image, which can potentially change highlights and contrast. If you're proofing to an inkjet printer, this method is your best bet for displaying an accurate screen image.
- Perceptual. You might prefer this method for documents with vivid color, such as scanned photographs or digital camera captures. The Perceptual method compresses a larger gamut of colors to fit a smaller one by desaturating all colors.
- Saturation. This less complex method maps colors between devices directly, regardless of the differences in lightness, saturation, or hue. It's suitable if only solid colors are involved and if color accuracy and consistency are not required.
- Automatic. This method is the default and perhaps the best choice for general use. With Automatic selected, vector object colors are mapped with the Saturation method, and bitmap colors are mapped with the Perceptual method.
Keep in mind that different rendering intents give preference to how certain colors for different object types are corrected and displayed. The method you choose will depend on whether your CorelDRAW Graphics Suite 12 document consists of vector objects or bitmap objects, or both, and on the color range of your devices.
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