Does painless RGB to CMYK conversion exist?

Jun 1, 2005 12:00 AM, By Julie Shaffer

Not without color management!

Binuscan offers the IPM Workflow Server, which promises to automate many aspects of image management from color mode conversion (based on ICC profiles or conventional separation tables) to image correction such as unsharp masking or gamma adjustments, and geometrical adjustments such as rotations, crops and resizing. Like most of these servers, IPM Workflow Server is a client/server solution and is compatible with Mac and Windows platforms.

Helios (Sacremento, CA), a company with long-time name recognition in the prepress industry, offers EtherShare OPI , a server-based image replacement product, which includes ColorSync/ICC-based color management. With EtherShare OPI, the high-resolution master image can be in RGB, CMYK or Lab color mode, while the corresponding low-resolution proxy image can be in CMYK mode. When the file ultimately is separated, the properly converted CMYK image is swapped in on the fly. (See www.helios.de.)

Alwan Color (Lyon, France) has positioned its CMYK Optimizer Server as both a preflight and image manipulation tool. CMYK Optimizer Server is based on hot folders, each of which can be associated with a series of tasks, including color inspection as well as mode conversion. Image files can even be directly imported into the server from an FTP location. As a preflight tool, CMYK Optimizer Server analyzes images placed in hot folders, generating a report of potential problems, including over-limit total area coverage or black ink issues and images requiring mode transformation. (See www.alwancolor.com.)

Enfocus (San Mateo, CA) Pitstop Server provides a similar service for PDF workflows. Pitstop Server is hot folder-based as well, and lets users preflight and perform any action that can be accomplished with Pitstop Pro to PDF files. For example, a folder can be set up to automatically detect RGB images or text in a PDF file and convert it to RGB and Black based on a specific ICC profile. (See www.enfocus.com.)

RGB to CMYK conversion also can be handled at the end of the production chain. While RGB to CMYK conversion is part of all Adobe CPSI RIPs, the default settings are not optimal for most printing conditions. Most prepress workflow solutions, such as Creo Prinergy, Esko-Graphics’ Scope BackStage server or Heidelberg Prinect MetaDimension (to name just three of dozens), integrate enhanced color management tools for both proofing and final output to film or plate. These systems can be set up to apply the right profile for each specific output device in the workflow. So deciding to image a job originally intended for one press to another at the last moment won’t make any difference in terms of color, when imaging properly tagged RGB images, because the RGB data will be converted using the right profile for that press.

RGB to CMYK conversion can be accomplished at the computer desktop, with a server-based solution or in the RIP. Any of these methods can work "painlessly," but all work best when some form of color management is used.

Julie Shaffer is the director of PIA/GATF’s Center for Imaging Excellence. Contact her at jshaffer@piagatf.org.