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5.2 CorelDraw

CorelDraw incorporates a CMS which is licensed from Candela. It is Kodak PCMS compatible and appears to contain the most comprehensive range of CMS features in the packages researched.

As mentioned earlier, three components of a colour management system are characterisation, calibration and transformation. Transformation is referred to in CorelDraw as colour correction.

Colour management in CorelDraw is divided into Basic and Advanced features.

5.2.1 Basic Colour Management

Basic colour management concentrates on the Basic System Profiles. A system profile indicates which monitor and printer are part of a desktop publishing system. It will also include a scanner if PhotoPaint is used. If a system uses a range of devices, then a profile must be created for each possible combination. Once these profiles are created, they can be reused every time the same device configuration is used.

To create a system profile the user needs to know the make and model number of the devices. The Colour Manager has built-in information for a large number of devices. The user does not need to know the technical properties of a device in order to select a profile.

By default AutoMatch is enabled in Corel Draw. This means the Colour Manager will automatically differentiate between bitmapped and vector objects. Vector objects are line objects created within CorelDraw. Bitmapped objects are imported pictures. The user can force the Colour Manager to optimise colour matching for line art by enabling Illustration. Enabling Photographic causes optimisation for bitmap.

So far, this is the same as basic Colour Management for any CMS.

5.2.2 Advanced Calibration Features

CorelDraw is a desktop application package that caters for a user having the knowledge and the need for advanced colour management. The advanced colour management features allow for the selection of new devices and the modification of default device settings.

These features are intended only for the expert user, but the instructions in the user manual are very clear. This section is divided into three, one for the three different device types.

5.2.2.1 Monitors

Select 'monitor devices' from the device profiles, and then select 'other' as a device type. This gives the user access to the calibration information. A dialog box appears where the user can enter the monitor characteristics. Corel warn that the Red, Blue and Green chromaticity is unlikely to require alteration, although they do provide for this. Clicking the mouse in the appropriate square sets x and y values. Gamma can be set with a slider bar. A slider is also available to change the white reference point.

5.2.2.2 Printers

If the need arises for a custom printer profile two stages are required, calibration and characterisation. A colorimeter or spectrophotometer is also required.

Calibration of CMYK printers requires the generation of a .IM file. This is a file of 320 reference colours defined in CIE XYZ values. CorelDraw comes with a selection of .IM files already, and there may be one that is a close match to the printer. If not, one has to be created by printing the CMYK320 reference colour pattern and measuring the colour in each of the 320 squares.

Calibration of RGB printers is slightly less time consuming as the RGB reference patterns consists of only 80 squares. Of these, only the grey squares need to be measured. These values are loaded into a .GRY file.

Characterisation can be done in one of two ways. Visually using a calibrated monitor, or from test patterns.

Choosing visual characterisation causes a reference pattern to be displayed. The same pattern can be printed. The user can then adjust the reference squares in the display until they visually match the printed pattern. Adjustments follow the Hue, Lightness, Saturation model.

A Colour Match File gives a more accurate characterisation by printing a test pattern and using a colorimeter to measure the CIE XYZ characteristics. These can then be put into a .RHN file.

Once the component files are loaded, the user clicks on Color Match and CorelDraw (Candela) will then create a profile unique to the printer.

5.2.2.3 Scanners

Scanners are calibrated by comparing an image scanned in by them to a reference target. Corel supply a calibration target or an IT8 target can be used.

IT8 targets consist of a range of colour squares. The Corel target has a smaller range of squares, but also includes an image. The image must be scanned in as raw data, with scanner calibration disabled. The scan must be saved as a .TIF file. This .TIF file is then compared with a .REF file corresponding to the image. The size of the image must be adjusted to cover a colour grid. The Color Manager will compare the values of the colours thus 'framed' to the values in the reference file and perform calibration accordingly. A scanner calibration file with the extension .SCN is then created, unique to the scanner used.

Corel Draw is the only package investigated that provides a user friendly interface for such comprehensive device profiling.


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