The previously mentioned lack of colormetrical evaluations as well as the rise of modern and inexpensive digital printers, such as inkjet photo printers, lead to widespread use of overly colourful prints sent to the printer as the reference for the OK-sheet. The printer often failed to reach the required appearance; reclamation and rework have been the consequences.
Though the question arose of how a digital print might be assessed on an objective basis in order to be a [technical realisable] colour reference for a given printing condition using a reasonable control element to be imposed on each document. This has been the hour of birth of the “Farbverbindlichkeit” – the colour reliability. Though the colour
reliability is a property that has to be checked for each site or document separately. For that reason, a compact control wedge, like the Ugra/Fogra Media Wedge CMYK, reflecting the trade off between a small size and a good correlation to the page content is essential for an easy assessment of the colour reliability. That automatically rules
out test charts, such as the ECI2002, or charts testing the resolution or smooth vignettes for each print in the daily production. Such tests had to be scrutinized in the past by the means of the system or creation certification to be explained in the next paragraph.
A proof becomes a contract proof or a colour reliable proof only when certain criteria are met. The MediaStandard Print [MSD] published by bvdm, a technical specification and an accepted trade standard in the graphic arts industry, requires the Ugra/Fogra Media Wedge, the compliance to colorimetrical tolerances taken from ISO 12647-7 as well as a complete human readable status line as prerequisites on each print. A label to be printed on each proof comprising the pertinent information often documents this. A colour reliable proof therefore guarantees that a printer, meeting the ISO aims, such as solid coloration and tone value increase curves derived by a suitable process calibration, can be assured that they can reach the given appearance by using the over and under inking capabilities of their press.
Trade associations or companies being active in different regions or markets and using other aims, such as those defined in the MSD, may define colour reliability differently. They might define other control elements, pick or alter other requirements from ISO 12647-7 or add individual requirements to check a typical proof for the daily production.
