Maximum Total Area Coverage (TAC)
Depending on printing conditions (printing process, paper, drying method, etc.), the maximum permissible total ink coverage (total area coverage, TAC) is limited. The allowable total ink coverage depends on the production conditions and the type of paper used. Total ink coverage directly affects, for example, drying time. Under certain production conditions, "set-off" may occur, meaning the printed sheet or page can transfer ink onto other sheets or pages.
The total ink coverage is calculated as the sum of the percentage values of the CMYK components. The minimum possible ink coverage in a four-color process is 0% (C:0% + M:0% + Y:0% + K:0%), and the maximum is 400% (C:100% + M:100% + Y:100% + K:100%).
The following table shows converted values for the darkest possible black (CIE Lab* = 0;0;0) for three example profiles:
| Profile | Cyan | Magenta | Yellow | Key | Actual TAC | Maximum TAC |
|---|---|---|---|---|---|---|
| ISOcoated_v2 | 88% | 79% | 65% | 93% | 325% | 330% |
| ISOcoated_v2_300% | 78% | 68% | 58% | 94% | 298% | 300% |
| PSR_PLUS_V2_PT | 93% | 88% | 93% | 85% | 359% | 360% |
These examples show that the same color (aimed at optimal reproduction) produces different CMYK values depending on the profile used for conversion. It is also evident that during conversion, the available range is nearly fully utilized. The actual TAC almost reaches the maximum allowable TAC. Due to mathematical rounding during conversion, the DUON portal allows a tolerance of +8% total ink coverage (corresponding to a potential error of +2% per color).
How to Identify Elements with Excessive Total Ink Coverage
Adobe Acrobat
You can check the ink coverage of your document directly in Adobe Acrobat Pro:
Open your document in Adobe Acrobat Pro.
Go to View > Tools > Print Production > Output Preview.
In the Output Preview window, enable Total Ink Coverage and set the limit to 300% for offset printing or 360% for gravure. Areas exceeding the limit will be highlighted in neon green.
Adobe InDesign
InDesign provides a Separation Preview to visually highlight elements with excessive TAC:
Go to Window > Output > Separation Preview.
In the palette, select Ink Limit and set the threshold (e.g., 300%).
Hovering over areas with the cursor displays the total ink coverage at that point.
Adobe Photoshop
In Photoshop, you can also check ink coverage:
Go to Window > Info.
In the Info panel, open Panel Options.
Set First Color Readout → CMYK and Second Color Readout → Total Ink Coverage.
Common Causes
Significant post-conversion color adjustments
Profile conversions only work with the current color values. For example, converting the darkest possible LAB black (0;0;0) to ISOcoated_v2_300% results in CMYK 78;68;58;95, with a total coverage of 299%. Subsequent adjustments to CMYK values (e.g., via curves) may increase total ink coverage, even if the correct profile was applied. In such cases, a two-step conversion is recommended.Confusion between "Assign Profile" and "Convert to Profile"
These two commands serve completely different purposes:Assign Profile: Interprets the stored color values as if they belong to the specified device profile. Use when the source profile is unknown (e.g., image from unknown camera).
Convert to Profile: Converts the device-specific values from the source profile to the target profile via a Profile Connection Space (e.g., CIE Lab*), preserving the perceived color. Always use this for actual profile conversion.
Transparency Mode "Multiply"
Semi-transparent elements in InDesign may cause excessive TAC when using the Multiply blending mode.
Solutions
Round-Trip Conversion
Perform a round-trip conversion through LAB to reduce excessive total ink coverage without affecting quality:
Convert high-TAC CMYK to LAB.
Convert again to the desired CMYK profile.
This ensures the darkest values are appropriately limited according to the profile’s lookup tables (B2A tables).
Convert to Target Profile → LAB
Convert to Target Profile → CMYK (select the corresponding profile)
Transparency Mode "Multiply"
If possible, create semi-transparent elements directly in Photoshop or choose a blending mode other than Multiply in InDesign.
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