Since 2009 PSOUncoated has been the standard profile for uncoated paper. Nevertheless, proof service providers often have the problem that at first glance proofs on PSOUncoated often differ significantly from the print result. Immediately visible: the white point of the paper.
The PSOUncoated paper white looks very grayish. If, for example, PSOUncoated is proofed on an EFI 9120 XF paper, which actually has a neutral white coloration as paper, then the paper must be recolored by the printer in terms of paper white. This paper-white simulation makes the proof look “grayish” and often not “bright white” like the real production paper. “I can’t put this down to my client” proof service providers often hear from the agencies and designers who commission proofs. And frankly, printing on bright white uncoated paper will also differ significantly from the PSOUncoated Proof result depending on the paper selected.
Some proofing services still proof uncoated paper according to ISOUncoated, because the paper tone is much whiter and not so grayish. In the medium term, however, this will not overcome the misery: PSOUncoated is the current standard according to which the process standard for offset printing certified print shops are also based. But in the pressroom the differences between norm and reality often become apparent. If the new D50 standard light according to ISO 3664:2009 with higher UV components is used for inspection at the printing table, then proof and printing result can often only be matched very poorly. And due to the long standardization periods, this problem will continue to accompany printers and proofing service providers for quite some time to come.
Colour is colour, you’d think. That’s right. But have you ever tried to explain the colour of your new car or your new red wallet to a friend on the phone? You will notice that human colour recognition and the reproduction of the same in another medium is very difficult.
The same applies to computers – better: monitors, and printers – i.e.: laser printers, inkjet printers or newspaper printing or offset brochure printing.
Why is the red on a monitor different from exactly the same red printed on paper? It’s simple: put the paper in front of the monitor. The two shades of red are exactly the same. Like this. And now you’re completely darkening the room. What do you see? The red on the monitor is still red. And exactly the same red on paper? This is black now. Why is that? Very simple:
A monitor adds light, i.e. spectral components, to the existing ambient light. If you see red on a monitor, it is because the monitor actively emits red light.
And now the paper: When do you see red on paper? Exactly when white light falls on the paper, for example through a window or a lamp. And when do you see the colour red on paper?
When white light falls on the paper and the paper extracts the non-red spectral components from the white light and reflects the red light. That’s when you see the colour red.
One colour, two completely different ways of production. And this is exactly where the colour calibration and the proof start. The strategy? Fairs. And this under fixed conditions and not with the human eye, but with “incorruptible” technology.
Put simply, a monitor calibration device can measure your monitor and see exactly “how much” colour your monitor can display, and “how wrong” your monitor can display colour. And if your computer knows that, it can correct the monitor.
Another measuring device can emit neutral white light onto a paper and measure the reflected colour. Depending on the printing process and paper, the ink looks completely different, but the meter again sees “how much” ink the print can represent and “how wrong” the print represents ink. And if your computer knows this, it can correct it. And:
If the computer knows the colour representation of the monitor and printer, it can correct and adjust the representation so that both correspond to the same colour. Of course, this only works if the colour and brightness of the light that illuminates the paper is also known and standardized.
And how does the proof work? Very simple:
If a computer also knows that the final printed product is to be printed in offset on an image printing paper, and it knows the colour representation of this printing process, then it can simulate this on a monitor and on an inkjet printer.
On the monitor, this colour-accurate representation is a so-called “soft proof”, the colour-accurate preview of the subsequent print on the inkjet printer is called “Proof” or “Contract Proof”.
This inkjet printing must be very precise and meet the highest demands in gamut and colour simulation. And since the image processing technology, colour matching calculation and measuring technology behind it is not very cheap, proofs are still mostly “expensive” inkjet prints. Due to new printing systems and inexpensive and better measuring technology, however, prices have also fallen significantly here in recent years.