Digital proofs (correct: contract proofs) are an ISO-certified test equipment for the graphic arts industry. Digital proofs simulate the colourfulness of offset or gravure printing in a colour and legally binding manner within the narrow tolerances of ISO 12647-7. Today, they are almost exclusively calculated using a RIP and then produced with inkjet printers on special proof papers.
The proof data is converted into separations, then reassembled into a composite image to correctly simulate overprinting and trapping. The data is then transferred as a newly created composite image to an inkjet printer, usually with more than 8 colours, which prints the data. In addition to the print data, digital proofs must also carry a UGRA/Fogra media wedge in order to be colour-consistent and legally binding. Thanks to the standardised wedge, the printer is able to check the proof for correctness. Since many printing houses do not have this measuring technique at hand, the proof is often provided directly with a test report that shows the correctness of the measured values of the media wedge directly on the proof.
Earlier methods such as Chromalin etc. are no longer available on the market today.
In addition to the term “digital proofs”, terms such as colour proofs, proofs or online proofs are still in common use.
ISO 12647 defines the highest standard of contract proofs, or “proofs” (ISO 12647-7), as well as the term “validation prints” (ISO 12647-8). Validation Prints are characterised by the fact that although they are less accurate in colour, they can also be produced on laser printers. Compared to contract proofs, however, they accept much higher colour deviations and are only legally binding after prior consultation. Real “proofs”, i.e. true contract proofs according to ISO 12647-7 are currently not only by far the best variant in terms of colour but also the only legally binding proofs.
PSO stands for “ProcessStandard Offset Printing”, a standard that was developed by Fogra and the German Printing and Media Industry together. The ProcessStandard Offset Printing is a set of standards for offset printing. With test equipment and control by measurments as described in the PSO, the printing process of the data delivery and data preparation on the platemaking is monitored, controlled and checked.
The following standards are summarized in PSO – “ProcessStandard Offset Printing:
ISO 00005-4: Optical density
ISO 02846-1: Printing inks
ISO 03664: Standard Lighting
ISO 12218: Platesetting analog
ISO 12641: Scanner Testchart
ISO 12642: Output test charts
ISO 12646: Monitors
ISO 12647-2: standard pressure
ISO 12647-7: Digital Proof
ISO 13655: Spectral color measurement
ISO 13656: Densitometric and colorimetric measurement
ISO 14981: Densitometer