When you select Separate RGB/Lab to CMYK source, the Fiery server converts the original RGB colors in a document to the source CMYK profile selected in Job Properties before converting to the output profile of the press (as defined by the Output profile print option). The color reproduction from converting RGB colors to the CMYK source and then the output color space is similar to converting the RGB content to that CMYK source profile.

For example, the color reproduction from converting RGB colors to the CMYK source in the Fiery server is similar to converting an RGB image to a CMYK profile in Adobe Photoshop. Another helpful technique with Separate RGB/Lab to CMYK source is to use a high-quality ICC profile for another press, define that high-quality ICC profile as the source CMYK profile in the Fiery server and simulate the color appearance of RGB colors by the other press.

You can use this feature with PDF/X workflows to convert all color spaces to CMYK source before conversion to the output color space. These workflows require device-dependent colors (RGB or Grayscale) and device-independent colors (ICC or L*a*b*) to match the document's CMYK content. With the introduction of PDF/X-4 allowing transparency in a PDF/X document, the feature also supports CMYK overprinting included in designs that have transparency effects. A best practice for rendering transparency is to select the Separate RGB/Lab to CMYK source print option because rendering transparency requires complex processing policies to achieve the desired appearance.

When the Separate RGB/Lab to CMYK source check box is cleared, the Fiery server manages all RGB colors with the output profile. This workflow renders the RGB colors with the full gamut of the output device and is a best practice when you need the most vibrant color achievable with the printer.