COLOR & INK
RGB, CMYK, ICC profiles and TAC: decide for the printing condition
A color is not correct merely because it is CMYK. Preflight must connect its values, profiles, spot inks and ink load to the requested production process.
Reviewed 24 August 2026
Key takeaways
- RGB and CMYK describe different spaces; conversion depends on profiles and rendering intent.
- The output intent identifies the output condition targeted by a PDF/X file.
- TAC is the sum of ink components at a location, not one global file property.
- Automatic conversion is safe only when target and content type are explicitly authorised.
Separate color spaces from production intent
RGB normally describes color through light, while CMYK describes process-ink quantities. Moving between them requires a color transform; simply rearranging numbers is meaningless.
A PDF can contain DeviceRGB, DeviceCMYK, calibrated spaces, ICC profiles and spot colors. The report should identify affected objects so the operator knows whether an issue comes from an image, vector object or named resource.
ICC profile and output intent
An ICC profile describes a colorimetric relationship. In PDF/X, the output intent communicates the reference printing condition. It does not automatically transform every object, but gives the workflow an interpretation target.
The profile must match the process, stock and agreed parameters. Arbitrarily embedding a CMYK profile can make a declaration look more complete while describing the wrong production condition.
Understand total area coverage (TAC)
Total area coverage adds cyan, magenta, yellow and black percentages at one location. A rich black with every channel at 100% represents 400%, while black using K alone represents 100%.
The acceptable limit depends on output characterization, stock, press, drying and separation strategy. The production profile should carry the expected value; one universal limit can reject good files or accept excessive ink.
Spot colors, ink names and overprint
Spot colors represent named inks. Two almost identical names can create separate plates, while objects sharing a name should describe a coherent ink.
Overprint may be intentional for black and dangerous on a white object. These checks depend on design intent and should provide page, object and value instead of silently converting every color.
What can be corrected automatically
Vector RGB-to-CMYK conversion can be deterministic when source interpretation, output profile and rendering intent are fixed. Vector grays can be separated to black according to an approved rule.
RGB images, spot colors, complex blends and results likely to change visible intent should remain reported or move to REVIEW. Every authorised conversion must create a new output, retain the original and run preflight again with the same versioned profile.
Reference sources
- Embedding and referencing ICC profilesInternational Color Consortium
- Print using spot colorGhent Workgroup