This page describes the process for converting an RGB file to CMYK for printing on an offset press. Files coming into this workflow will have originated as either RAW files that have been processed in a RAW converter such as Adobe Camera Raw, or as a RGB master files that have been optimized in Photoshop.
The primary objective of every RGB-to-CMYK conversion is to preserve the color and tonal range of the original image. This is achieved through rigorous adherence to best practices in both color management and image file adjustment. The RGB-to-CMYK workflow is not a creative process: color and tonal choices have been made upstream during the capture and editing parts of the workflow. Predictable rendering is the goal of the CMYK conversion process.
READ MORE ABOUT COLOR MANAGEMENT IN The color SECTIOn
There are three essential partners in the CMYK workflow: photographers, designers and printers. A successful CMYK project relies on all three partners reading from the same page and being in agreement on the basic moves required to get from "here to there". Currently, most printers require that files be submitted to them already converted to CMYK. It is typical for photographers to do the conversion and deliver those files to the designer press-ready. However, at the outset of every project, you should communicate with your workflow partners to be sure you are all in agreement as to who does what.
READ MORE ABOUT THE CMYK PRINTING PROCESS IN The color SECTiON
|Figure 1 This video shows Step One and Step Two: bringing the file into the workflow and creating a "sound RGB" file.|
|Figure 2 This video shows Step Three and Step Four: soft proofing and converting to CMYK.|
Figure 3 These are the steps for converting from RGB to CMYK. Because of the collaborative nature of the RGB-to-CMYK workflow (photographer shoots pictures, designer incorporates pictures into layout, printer runs press), it's important to standardize the workflow to insure predictable rendering from original image to final press sheet. The following video tutorials walk you through each of these steps.
Confirm that Photoshop's Color Settings are configured to preserve color management throughout the workflow.
When bringing a file into the workflow, confirm that it is color managed. This means that the file contains an embedded ICC profile.
When a file comes into the workflow and is not color managed (meaning there is no profile embedded), assign the profile that gives the most accurate on-screen color.
Once a file has been optimized in RGB, save it with "_master" appended to its file name.
READ MORE ABOUT PROPER FILE NAMING CONVENTIONS IN the File Management SECTION
When soft-proofing and converting to CMYK, it's critical to choose the correct CMYK profile. Make the choice based on the final offset printing conditions. If the printer is known, ask for their CMYK output profile. If the printer is unknown, make your best guess based on what type of press/paper the job will be printed on.
Rendering intent controls how out-of-gamut colors in the source file (RGB) are handled when converted to the CMYK output color space.
Once the file looks good in soft-proof, convert to CMYK.
Once a file has been converted to CMYK, save it in TIFF format with "_cmyk" appended to its file name.
Good RGB to CMYK conversion is both an art and a science, but it is not rocket science.
Editor's Note: We highly recommend Rick McCleary’s CMYK 2.0 as a good guide to this process as well as Digital Photography Best Practices and Workflow Handbook.
Digital Photography Best Practices and Workflow Handbook