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Contents
For those new to this field it is necessary to point out that there are also very fully featured image manipulation packages which do not contain CMS, but will offer considerable control of colour. These latter packages will gradually benefit from the OS extension approach which has been adopted by Apple and now Microsoft.
No mention is made of system requirements in the following sections as they are so variable, depending on exactly what configuration of package is required. It is often possible to cope with less main memory at the expense of disk space. Furthermore, users of typical applications packages in this field would do well to be using generously specified machines, whether or not they are using CMS. For example, PCs with less than 16Mb memory are likely to be slow. Rather less memory is required for a typical Mac equivalent.
The EfiColor CMS uses device profiles to ensure that colours are accurately converted across devices as described in section 2. EfiColor profiles support scanners, monitors, digital colour printers and off-set presses. To accurately convert colours between a monitor and a printer the EfiColor CMS creates a colour transformation that is composed of the monitor profile and the printer profile. Where a colour in the monitor's colour space cannot be produced in the printer colour space, EfiColor will automatically convert to the closest matching in-gamut color.
Colours in an application are either created with the application's palette or imported as part of a colour picture. The meaning of the colours in an imported picture is determined by the scanner or monitor used to generate them. The EfiColor XTension supports a colour interchange standard called the Metric Colour Tag (MCT). This allows applications to tag TIFF, PICT and EPS files with the colour meaning of the file. EfiColor can then accurately render the colours on any other device, subject to the device's limitations. EfiColor automatically reads the MCT information (if it is in the file) and assigns the appropriate Efi profile. If the MCT information is not there, then EfiColor allows the user to assign colour meaning to a file by associating a device with it.
Thus in QuarkXPress, the menu for importing a picture also allows the selection of an Efi profile. It also provides a preview of the picture, so the choice of profile can be amended before the picture is actually read in.
EfiColor allows the user to assign colour meaning to every element, e.g. a scanned in photo, on an application page and will automatically perform the colour transformations needed. EfiColour compares colour tags for every colour element with the colour profiles for the monitor and printer. If they match no further action is needed. If they do not match then the colours are converted. When a user creates a new colour, then a gamut alarm will indicate if the colour cannot be represented on the chosen printer. This warning allows the user to modify the colour if required.
The EfiColor system uses Efi profiles. A number of these are provided with QuarkXPress. Quark's documentation states that more profiles can be obtained from Efi, who are constantly adding new profiles to the range. For devices that are not covered by a specific profile, the user can set default profiles. There is a default profile for RGB and another for CMYK.
The QuarkXpress documentation does not mention user creation of profiles. The Efi profile cards indicate the device calibration required to achieve a true colour match, but the manual does not mention the creation of profiles for a different calibration. This may be omissions in EfiColour, or it may be beyond the scope of QuarkXPress.
QuarkXpress on the Mac does allow hands-on colour correction. This is effective for an individual TIFF image, but not for parts of an image. This facility allows the alteration of hue, lightness and saturation independently or in combination. This is a mouse driven feature. When selecting Contrast from the Style menu, a little graph appears. Hue is represented as ranging through the rainbow, lightness from darkest to lightest, and saturation from light to heavy. The line on this graph can be pushed up or down as a whole, thus making changes across the full range, or individual spots can be adjusted, e.g. the lightest can be made darker, and the red of an image can be reduced in relation to the blue and green.
This requires an expert touch, but can be used to heighten or smooth the contrast in a picture, or lighten or darken it. This is only available on the Mac and when Quark incorporates the Efi Xtension. It is not clear at this point whether this is an aspect of Efi or of Quark.
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