Since November 2016, the test criteria for Fogra-certified contact proofs have been updated, incorporated into the stricter ISO 12647-7:2016 standard.
Why this change
Fogra showed through measurements that the old tolerances had a ∆E value too high relative to visual assessment — people spot colour deviations more easily than that measure suggested. The new Delta-E values are far more "equidistant" and thus better aligned with human colour perception. Where the old measure (HC) depended mainly on hue angle, the new measure (Ch) describes the actual distance of a colour pair in the CIEa*b* plane — more true to life.
Tolerances
Spot colours (PANTONE, HKS, TOYO): optionally evaluated within ∆E 2.5;
Process colours (cyan, magenta, yellow, black): may deviate up to ∆E 3.0.
Why this question?
GrafiStore provides solutions for HP EPM workflows. EPM (Enhanced Productivity Mode) is HP Indigo technology that translates CMYK to CMY, saving ink and speeding up the machine. Whether a PDF is suitable for EPM is checked with Enfocus Switch and the HP EPM module; you decide whether to meet the ISO standard exactly. EPM+ converts jobs with multiple black-and-white pages to greyscale.
In one example: if a page uses more than 10% rich black it goes to the CMYK flow; below that, ∆E and ∆C checks are run against the tolerance. Previously there was a tolerance up to ∆E 5.0 — deviations most people do not notice. Clients needing brand accuracy/high-end quality are always checked more strictly. Excellent EPM results have also been achieved with photo books.