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Colour management does not need to be as difficult or expensive as is often suggested. It is basically the process of ensuring that colours are accurately reproduced throughout a system and hence repeatable on other calibrated systems. It starts with the monitor because inaccurate colours mislead the viewer and incorrect prints inevitably follow. The simplest approach is to adjust the monitor by eye to achieve good brightness and contrast. Various software tools can help with this, but they all rely on eyesight which varies from person to person. A better approach is to calibrate using a colorimeter designed specifically for the purpose.

It is clearly important that the software used for image manipulation supports colour management. Try opening the same image in several different applications at the same time, and observe the differences. Applications such as Photoshop manage colour correctly, but free software bundled with scanners or digital cameras may not.

The capabilities and dynamic ranges of input devices such as cameras and scanners are different from those of output devices such as monitors and printers. The range of colours that can be reproduced by a device is known as its colour gamut. When an input device has a colour gamut that exceeds that of an output device, the colours that cannot be directly reproduced are compromised.

The basis of colour management is therefore to produce a workflow that transfers from device to device absolute colour values. Unfortunately, many devices work with RGB or CMYK values that define only how a particular colour is read or produced on that particular scanner, computer or printer. The transfer accurate information to another device in the workflow, it is essential to characterize the behaviour of each one. This information is stored in a characteristic curve generally known as a profile.

Using the colour information from the originating device, combined with the relevant profile data, it is then possible to transfer accurate colour information along the workflow. However, the profile of the second device must now be used to once again translate the colour data. Only then can the second device regenerate the original correct colours.

In a closed system, that is one in which the same input and output devices are permanently connected, this may be difficult enough. However in an open system, where images are transferred electronically to another independent closed system such as that used by a publisher, accurate colour reproduction is possible only when both systems are properly calibrated. If an editor calls to say that images look too blue, one or both of the systems is in error.


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