LESSON 15 COLOUR M ANAGEMENT IN CORELDRAW STRUCTURE 15.0
OBJECTIVES
15.1
INTRODUCTION
15.2
SETTING COREL COLOUR MANAGEMENT SYSTEM 15.2.1 COMPOSITE AND SEPARATION PROFILES
15.3
EVALUATING MONITOR
15.4
SUMMING UP
15.5
POSSIBLE ANSWER TO SELF-CHECK QUESTIONS
15.6
TERMINAL QUESTIONS
15.7
REFERENCES AND SUGGESTED FURTHER READING
15.8
GLOSSARY
14. COLOUR M ANAGEMENT IN CORELDRAW In Lesson 15 we will learn to set the colour management system in CorelDraw. This is a pre- requisite to stimulate the digital system to the print system. It also makes the monitor more colour accurate.
15.0 Objectives After going through this lesson you should be able to •
Understand colour management in Corel Draw
•
Differentiate colours display on Monitor and that on Printing
15.1 Introduction Colour Management System is the way of handling with colours by the computer system in displaying them on screen and in printing them out on any media. You may find that the colors displayed on your monitor donot match the colors of a scanned image or of a printer's output. Color management lets you reproduce colors accurately by using color profiles and by correcting colors for display. In this section, you will learn about • understanding the Color management dialog box • working with color profiles • choosing advanced color management settings • correcting colors for display
15.2 Setting Corel Colour Management System Corel's Colour Management System is Kodak Colour Sync 2, used by Adobe applications, Windows 98, and Mac OS. Corel Colour Manager 7 and Corel Colour Profile Wizard 8 are the same systems with little differences in the way dialog settings display. Version 8 will be dealt with in this lesson. However, those running version 7 can easily compare and apply this method. Run Corel Colour Wizard 8 to get the dialog box shown in Fig. 15.1. In Device, select Monitor. In Profile, select Generic Profile, and then click the Tune button.
Fig. 15.1 First Dialog box of Corel Colour Wizard 8
The next dialog, Fig 15.2, will ask to specify the monitor manufacturer, model, and any annotation to be added. Click Next.
Fig. 15.2 Second dialog box of Corel Colour Wizard 8
If the monitor has a profile, select copy another monitor characteristic and point to the factory monitor profile. Leave this option blank if there is no profile and click Next.
Fig. 15.5 Monitor calibration
Since most users do not have a device to calibrate other than their eyes, please do not check this option (Fig. 15.5). Click Next. In the dialog box shown in Fig. 15.5, select Monitor White Point of 5000 Kelvin. In Gamma section, check identical RGB value, and type 1.8. Now check Red and open video card application dialog where gamma controls reside. Move this window to see the Corel wizard's red colour swatches. The Matrox Millenium II controls are shown in Fig. 15.6 below. Click and hold Red handle and move it until the red colour swatches match each other. Move away from the monitor to a Fig. 15.6 Matrox Display Properties
distance not to discern the line dithering in the left swatch and /or squint eyelids until dithering disappears. Repeat this process for Green and Blue selecting them in the Corel Wizard and moving the sliders for video card. When all three colours are set, click OK. If the video card has numerical gamma controls, set it to gamma 1.8, and do not match swatch colour. 15.2.1 Composite and separation profiles Place Corel CD#1 in CD drive. In the Corel Colour Profile Wizard's main dialog select Device Composite Printer. For Profile, select Get Profile from disk. Point to the / colour folder on the CD. Select the eight profiles named Generic US Negative Proofing. These profiles are SWOP (Specifications for Web Offset Printing). SWOP dictates the total ink value in any area. They have different GCR and Total Ink coverage. Light Gray Component Replacement is recommended in most cases since it controls how much of the black in the shadows will be replaced by CMY. This prevents over-inking of cyan, magenta, or yellow that will affect the basic hue. When major parts of the image are light and neutral, GCR helps guard against the possibility of colour variation on press. Total ink selection depends on press conditions, and the quality of paper. Lesser-quality paper requires less total ink. Select the same profiles for Separations Printer. Using the same profile in composite and separations may help to match proofing with final press print. These profiles give good results on Canon 610 inkjet, Xerox DocuColour, Indigo E-Print 100, and to output film from different imagesetters. The film negatives have been used to print to different quality paper, and presses, including full colour newspaper ads. Newspaper is the lower quality paper, and the most difficult printing conditions. Now that Corel Colour Manager is set, we need to evaluate our monitor, and fine tune our calibration.
15.3 Evaluating Monitor The brightness setting of our monitor affects gamma. This is why it is very important to set it properly. Figure 15.7 is a gamma space 1.8 image optimized to set the monitor gamma, brightness, and contrast properly. Before start to evaluate, the monitor should be running for 30 minutes or more. 1.8 gamma image should be displayed in the browser. Browsers do not have colour management systems, which is why it is the proper place to display this image for correct monitor calibration. It can also be opened in CorelDraw or Corel PHOTOPAINT with Corel's Colour Management disabled. If running in Windows 98 and if the Windows 98 Colour Manager System is set, disable it.
Fig. 15.7 Gamma space 1.80
Set the Contrast knob of the monitor to maximum. Increase the Brightness knob of the monitor so that the cheeseboard in the 0.4% strip is visible then decrease the Brightness knob until the 0.4% cheeseboard just fades away (at reading distance). Then evaluate the levels 0, 1 and 2 in the Black-Point swatch. The step from level 0 to level 1 should appear similar in amount to the step from level 1 to level 2. In cases where the step from level 0 to level 1 is larger than the step from level 1 to level 2 then decrease the Brightness knob until the steps appear to be equal. Evaluate the gamma swatches. If they do not show good overall matches then open the video card gamma settings and readjust gamma sliders. Gamma swatches must be viewed at such distance that the dithering is fully averaged by the eye. This is about 2 to 3 meters away. For those with video cards that do not support gamma control, follow the above proceedings using the image in Figure 15.8 optimized for gamma 2.5.
Fig. 15.8 Gamma space 2.50
Open Corel's Colour Profile Wizard and follow these steps until the dialog where the gamma swatches reside is reached. Check to see if they match each other when viewed at a distance. If everything is fine, close the Colour Profile Wizard and open Corel PHOTO-PAINT. In Photo-Paint, activate Colour Manager. Select any RGB image and convert to CMYK. When conversion is done it should not be noticed. Images should display the same in RGB and CMYK. However, colour Managers are not 100% reliable, they may do well, but under certain conditions they do not. Several colours that display well on the monitor cannot be reproduced in print. Reading CMYK is preferable than Colour Manager. Read the shadows, highlights, and neutral colours after a CMYK image is done. Adjust them using curves. Shadows should be C80 M70 Y70 K70. Highlight C5M2Y2K0. Reading CMYK and adjusting them results in good prints always.
Self-check Question 1. What is Printing Profile? 2. Give an example of one of the standards for profiling a colour? 3. What are composite and separation profile? 4. What is colour management?
Activity 1. Try setting colours as discussed.
15.4 Summing Up In Lesson 15 we have learnt the use of colour management system which helps in colour correction and colour conversion. We also learnt to evaluate the monitor and advantage of reading CMYK over colour management system.
15.5 Possible answers to Self-check Questions 1. Printing Profile are the specifications of displaying colour on the attached devices. Monitor Display colours using RGB, therefore colours are evaluated to fix the combination to display more colours this is known as profile for Monitor. Similarly Scanners, Colour Printing and other devices are used for creating profiles using other colour files eg. CMYK.
Profiles also work in pairs. One profile is used as the destination. The source profile describes colours of a particular device. 2. CIE L*a*b* colour space is one of the colour standards used by the textile industry. The CIE, international Commission on lighting, states that every colour the human eye perceives could be defined using three numbers: L* indicates luminosity, lightness from white to black. The a* and b* are the chromaticity coordinates that indicates colour directions: • +a* is the red direction, • -a* is the green direction, • +b* is the yellow direction, • -b* is the blue direction, The center position is achromatic i.e. sets hues of gray. As the a* and b* value increase and the point moves out from the center, the chroma or purity of the colour increases A design is printed, based on the printer/ink/media combination to insure that the colours in the original design or target colours match the digitally printed output. 3. These profiles are specifications for Printing. these dictate the total ink coverage. Light colour is recommended in most cases since it controls how much of the black in the shadows will be replaced by CMY. This prevents over inking of cyan, magenta, or yellow that will affect the basic hue. When major parts of the image are light and neutral, GCR helps guard against the possibility of colour variation on press. Total ink selection depends on printing conditions, and the quality of paper/cloth that is to be used. 4. Colour management Basics Colour Management is used for matching technology that is used to calibrate an imaging system and then allow the system to accurately transfer the ‘meaning of colour’ from one device to another. Each device in the system use an ‘ICC prifile’ to make this happen. Devices profiles are used as a strategy to make colour calibration easier and therefore more practical in creating better colour reproductions when scanning, viewing and printing. Each device has its own limitations and handles colour differently based on manufacturing specifications. Computer monitors are capable of displaying many more colours than one is able to print.
15.6 Terminal Questions 1. How does colour management system help? 2. Why is CMYK preferred over colour management system?
15.7 References and Suggested Further Reading 1. Help Menu & Tutorials of CorelDraw 2. Schwartz. 2000. CorelDraw 11 for Windows. Pearson Education India,
New Delhi.
15.8 Glossary 1.
Colour swatches Sample of colours(dyed cloth pieces or square colour patches on computer screen)
2.
Discern
Be aware of something clearly
3.
Dithering
Agitated, be uncertain
4.
Calibrate accuracy
Mark the scale or check the
5.
Profiles
Outlines, Brief biographical sketch
6.
Wizard Possessing outstanding skill in a particular field
7.
Squint Glance sideways