Effective colour management is a big growth area and it is vital to cut through the confusion in the market by allying proven technology with standard targets to achieve best results. By Laurel Brunner.

Even though awareness of the need to colour manage files within the digital workflow is rising, there is still a lot of confusion in the market.

Developers and distributors are under increased pressure to deliver inexpensive products, despite the often high cost of supporting powerful and complex technologies. Suppliers and users alike are wrestling with colour in order to make it as push button a process as possible, but can it ever be that simple ?

Risky investment

Lower cost, easier to use tools can add up to a risky investment when it comes to colour management. For the most part, general tools promising ease of use at low cost tend to be useless for demanding applications, but with colour management, this does not have to be the case.

The risk with low cost products is not necessarily that they do not work, but rather the fact that there is no margin in the price to allow suppliers to provide support. Users new to colour or to digital workflows should keep this in mind and be prepared to pay integrators and consultants for additional help, particularly at the implementation stage.

Apart from reducing the risk of failure, working with experienced consultants brings knowledge into the company that can be invaluable to effective colour managed workflow implementation. Just make sure that you develop in house knowledge at the same time.

Colour management is one of those areas that can yield results that are either a nightmare or a dream come true. Which of these applies depends on what drives colour management demand. High proofing costs, frequent make-good jobs and adverts, complex proofing cycles, multiple output types, the need to extract costs and frequent bottlenecks in the workflow are just a few of the drivers for colour management but defining the driver will help define the technology requirement.

Complex workflows

Whatever the drivers, colour management in the digital environment begins and ends with International Colour Consortium (ICC) profiling. At least it ought to. The reality is that most colour management begins and ends with the printer knowing how to get the best out of their press and associated proofing technologies. As workflows get more complex and the range of technologies and interested parties grow, proofing is particularly important for colour management. This is where the ICC's work is most directly applied.

Founded several years ago by Adobe, Agfa, Apple, Kodak, Microsoft and Sun Microsystems, the ICC's purpose is to define and promote standards and to provide a common processing model for colour managed workflows. There are around 70 active members of the committee, many of them colour scientists working to minimise errors inherent to data processing variations. The ICC has developed a Profile specification for defining the behavioural and spectral characteristics of devices used in a digital workflow. Those devices could be anything from a desktop scanner and computer screen through to a multiunit web press. Device profiles are used in conjunction with a Profile Connection Space, based on CieLab. CieLab (Commission de l'Eclairage et Illumination, Luminance, A, B) is a three dimensional colour space for calculating mathematical descriptors for colours based on three values: Luminance plus A, a measure of red-ness or green-ness and B, a measure of yellow-ness or blue-ness. The CieLab colour space encompasses a vast range of colours, including those out of gamut for printing devices and computer monitors. Colour management is all about calculating colour data within CieLab and remapping it accurately to the target colour space for output.

ICC progression

Over the last ten years the ICC's efforts have progressed hugely, at least in terms of the technology. Version 4.0 of the specification is now complete and there are plenty of success stories in the field, enough to encourage even the most wary of printers to look at digital colour management. The biggest problem confronting the ICC today is convincing printers that ICC colour management really does work, there are benefits, and that when it does not work it can be fixed.

Most colour management tools are developed to facilitate proofing and there are an awful lot of them on the market. ColorBlind's software suite offers tools for device calibration and includes useful features such as an option to allow the proofing engine to simulate offset printing. Monaco is another colour management specialist offering ICC-profiling tools and Epson and Xerox also use this technnology. GMG has developed a range of colour management utilities based on the Global Graphics Jaws RIP and GMG's own colour transformation engine. The engine handles colour transforms and GMG also has linearisation tools for calibrating devices to a common target.

Alwan Colour Expertise is a small development company that has developed quality control tools for assessing ICC profiles. ColorPursuit 1.0 can improve a colour production workflow's overall quality using sophisticated metrics and algorithms to assess ICC profile quality. It works by calculating profile accuracy based on errors introduced by profile tables in colour transformations, and also evaluates the specific reproduction of a source colour or image according to a given device and profile combination. Alwan's technology uses error analysis and Delta E deviations in order to identify data that could create colour inaccuracies at output and fixes it.

The company with the broadest range of colour management offerings is Best. Best's Premium Suite launched at the end of June supports everything from calibration and profiling, through to proofing and verification in distributed environments. Best's Premium technology is a colour manager for base linearisation and setting base colour management parameters. The Premium Suite adds to this RemoteProof, to support linked production across several sites. Best is now part of EfI and according to Wilfried Kampe responsible for Best's sales and marketing "EfI has made a firm committment to come into the graphic arts and Best has a well defined position in this scenario.

Clear idea

EfI was originally founded by Efi Arazi, founder of Scitex, and a man with a clear idea of the difference between high end colour solutions and low cost imitators. He once said that Scitex was like an Irish linen mouchoir, and EfI a two-ply tissue. They both do the same job but the experience is hugely different. As tissues took off and Irish linen mouchoirs faded from view, so EFI and its ilk have come to dominate the Rip and colour server markets. EfI counts both HP and Xerox amongst its Oem customers.

Creo is now responsible for Scitex prepress technologies including colour management. Creo's Profile Wizard is a suite of ICC based tools to facilitate colour manage throughout the workflow. Users can set up automated workflows and create their own profiles, as well as calculate linked profiles. A device link algorithm calculates a single profles based on multiple ICC device profiles. The idea is to tighten up the colour conversion calculations, and to minimise processing errors. The method also ensures preservation of the black channel so that black data is preserved.

For many printers digital colour technology can be quite daunting and many have found working with a distributor to implement a colour managed solution saves a lot of grief. John McDonald, managing director of Etek Workflow, sells EfI's products and is also a Xerox colour partner. John has found that colour management is best approached from a system level perspective rather than focusing exclusively on device profiling. "Where we have come across problems is the fact that profiling has to be a managed process. If you are profiling the press to emulate a digital press it is a profile based on the conditions at that time, so it has to be a managed process. Also you need to produce a profile for the paper types you are using."

He adds: "Where a customer has two digital presses and needs to load balance, we have found that the majority of profiles shipped with a Rip do not truly represent that output device's capability. We work with customers to optimise the profiles to ensure they all match the target."

Calibrated systems

According to Ray Donohue at printers Rayfount "the biggest problem on the digital side is consistency. Even with the calibrated systems we use, it's getting consistency over time. Rayfount has a Xerox 2045 and an Indigo digital press working side by side and has a very disciplined approach to workflow management.

Mr Donohue believes: "You have to follow procedures and just keep a eye on it from start to finish. When you have done a job today and the customer wants a rerun, you've got to be very careful to make sure it is the same." Clearly colour management applies at all stages in the workflow.

It should incorporate all input and output requirements, and user expectations. Users should develop their own calibration routines, and have their own spectrophotometer and profile making software. They need to approach colour management systematically, understand where colour production is vulnerable, and be able to anticipate what is needed to ensure smooth production processes.

Fine tuning

Successful colour management is all in the fine tuning, using proven technologies and working with standard targets such as the IT8 or Ksmart colour targets.

It is vital to digital workflows and cannot be considered in isolation, if it is to be made to work successfully. It can provide substantial financial and competitive returns, and is undeniably a rapidly growing part of the printing business.

Success requires being prepared and willing to invest in training and time, as well as technology. As Ray Donohue sees it "We're at the stage now when a lot of changes have to be made on the maintenance that affect the colour. We need to understand how to do this. Colour is a very big growth inside the trade that can't be ignored."

[时间：2003-09-15  作者：Bisenet  来源：Bisenet]