The Role of the RIP in Digital Color

Raster image processors (RIPs) control printing devices.

They translate, in a very direct way, the page description language of PostScript into a bitmap image, either CMYK or grayscale, including trapping, font data, formatting, kerning, color input/output profiles, bleed, imposition, metadata and legal validation. What you send to the printer gets translated into a picture the printer is capable of reproducing, and there you go.

They have become increasingly sophisticated and play a significant role in the Color management because they process files for printing on digital and offset output devices, including proofing and CTP systems as well as digital printing devices.

While you can get adequate results from a simple printer driver, which performs many of the same functions as the RIP, dedicated RIP software can offer a great deal more control, more finely grained tuning of files for fine art or production applications. RIPs can offer print queuing, batch processing, color separations, halftone screening, as well as checking for missing fonts or graphics.

An effective RIP incorporates such things as ICC-compliant color management system and profiles as well as workflow integration to deliver optimum results. It cannot operate as an isolated application with proprietary tools.

Rather, RIPs must integrate with a production environment and facilitate the exchange of color profiles among the various constituencies of the Color Management Workflow, including designers, agencies, prepress operators and print service providers.

Keep in mind that graphics creation packages allow users to create files that can be very difficult to print. Also, many designers have little in-depth knowledge about the printing process and are not aware that their designs create production issues. At a minimum, an effective RIP accommodates these complex constructs, so the final printed product closely matches the design intent.

It also widens the range of file types that can be accepted into the production process. In addition, an effective RIP should be able to handle special or spot colors and correctly process overprints and transparencies.

RIPs also concatenate variable data, pairing the context of a database expressed as a CSV (Comma Separated Value) text file with tags in a PDF file to replace the tags with variable data, whether words or pictures, based upon the values from the database.

Transparencies and variable data do not play well together, since Postscript is a layers page layout description language, and both of these items prefer to be the topmost layer in the stack, and when they have to fight it out, VDP usually wins over transparency. However, a properly tuned RIP can process these files correctly, ensuring the final PDF that goes to print is correct.

Each RIP handles color management the same way. Input color profiles are translated to L*A*B* values, which are then converted to the output color profile assigned to the RIP, and the resulting PDF file matches the output profile directly.

----------

Do you have a color management question, horror story or event to share?
Email me at reilley4color@gmail.com