In order for a digital hard proof to be certified and reliable (which means accurately reproducible on four-colour printing), it has to meet certain standards and have an authorized certification.
The ISO and Fogra certifications are the most reliable – specifically, the ISO Coated 39L or the Fogra protocol.
In order for you to identify a certified hard proof it must:
- be printed on certified paper (with a watermark on the back of the GMG, EFI, Kodak or Fuji logo)
- reference the printing profile, printing date, date of last calibration, printing system (RIP) brand and printer on the front.
- have a printed proof check colour bar.
- have a sticker label with the colour bar measurement results, their tolerance and divergence, as defined by ISO.
Sticker certification label
In order for all this to be more understandable, I’ll describe the hard proof printing process below.
Digital proofs are printed on inject printers which are regularly calibrated (at least once every 10 days) with a special calibration program (there are two basic programs, GMG and EFI).
Printer calibration with eye-one
The file is ripped and then printed along with the colour bar and the printing data. (printing profile, printing date, date of last calibration, printing system (RIP) brand and printer).
Each printed proof is checked with the eye-one (x-rite device), by rolling it over the colour bar.
Colour bar check
If it’s OK, then a sticker label referencing the eye-one check results is printed and signed by the operator.
Note: The lighting under which we look at a proof is very important. The right lighting is 5000 Kelvin produced by special lamps. As you can expect, it is possible that there could be differences even between two certified proofs due to the use of different RIP systems or printers and due to different algorithms or dyes (colours), respectively.