Total ink (TAC) limits by paper standard
Which total ink limits GCRflow offers for each of its four paper standards, the default limit of each, and how the limit relates to GCR strength. The tables are generated from the same settings file the converter and the API check against.
Limits offered
| Paper standard | Total ink limits you can choose | Default limit |
|---|---|---|
| GRACoL 2013 (CRPC6) | 260%, 280%, 300%, 320% | 320% |
| Fogra 27 (ISO Coated) | 260%, 280%, 300%, 320%, 340% | 340% |
| Fogra 39 (ISO Coated v2) | 260%, 280%, 300%, 320% | 320% |
| Fogra 51 (PSO Coated v3) | 260%, 280%, 300% | 300% |
Official presets: GRACoL 2013 at TAC 320%.
Default limit: the limit a custom preset gets when you switch it to this standard and its current limit is not offered there. Limits are offered in steps of 20 from 260% up to the highest value for each standard. Only coated paper standards are offered: there are no uncoated or newsprint standards, and you cannot upload your own ICC profile.
A TAC limit and GCR are two settings
A total ink limit caps the sum of C, M, Y and K at every point; for example, C60 + M50 + Y40 + K30 = 180%. GCR strength decides how much of the gray component that C, M and Y share is carried by black instead. In GCRflow you set both: the limit from the table above and the strength from GCR0 to GCR100.
Read GCR0–GCR100 as GCRflow’s strength setting, not as the percentage of gray component replaced. At low limits the two settings are linked: the lowest strength you can choose depends on the limit (next table).
Lowest GCR strength at each limit
| Paper standard | 260% | 280% | 300% | 320% | 340% |
|---|---|---|---|---|---|
| GRACoL 2013 (CRPC6) | GCR30 | GCR0 | GCR0 | GCR0 | — |
| Fogra 27 (ISO Coated) | GCR40 | GCR10 | GCR0 | GCR0 | GCR0 |
| Fogra 39 (ISO Coated v2) | GCR30 | GCR0 | GCR0 | GCR0 | — |
| Fogra 51 (PSO Coated v3) | GCR30 | GCR0 | GCR0 | — | — |
A dash means the limit is not offered for that standard. Rich-black boost can be turned on from GCR40 for every combination in these tables. Low Gray Enhancement and rich-black boost are used one at a time.
Where the limit is set
- Converter
- Official presets use the values above. A custom preset stores your paper standard, ink limit and GCR strength under your own name.
- API
- The icc and tac options of a job; combinations other than the default may answer 409 DEVAPI-PREPARING the first time. With mode=cmyk_only there is no ink saving, and CMYK values in the file stay as they are, without being brought within the limit.
- Output
- PDF: the ICC profile of the chosen paper standard is embedded as the output intent; for some combinations of standard and limit, a matching variant of that profile is used. RGB and CMYK TIFF: a CMYK ICC profile is embedded; grayscale TIFF files are returned unchanged.
- GCRflow API — Job options, including icc and tac.
- Case study: a boat photo — GRACoL 2013 at TAC 320%, before and after GCR.