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The myth of screened digital Ink Jet proofing

Don't be lost in the desert and buy sand ;-)

Again, many new products claim to manage to the miracle of simulating colors of offset presses while respecting their dot screening! Wonderful progress of on demand ink jet would finally have authorized this miracle - intended to preview the possible moiré effects on proof - whereas the very expensive and slow continuous ink-jet printers - even being much more accurate - never reached that point!

This is illusory for the following reasons:

Ink Jet printers Inks use much purer reflection spectra CMY primary colors than offset, and this in order to be able to simulate the colors of any offset-printed paper thanks to a broader color gamut.

For example, an offset magenta 50 % (M50%) apparent color will be simulated (under ISO D50 lighting) thanks to a suitable mixture of C'M'Y'K' inks of the printer. It is obvious that one could not at the same time respect the dot screening of the offset press and get the same color.

However, let us go further! Let us imagine the Ink Jet printer is using same inks and same paper as the offset press: this condition would be necessary but not enough to get same colors while having the same screen dots, because the optical part of dot gain largely depends on the penetration depth of inks in paper, and thus on the order and method for the inks application on paper. One would approach the press colors without reaching a good accuracy.

In conclusion, ink-jet proofing systems (or at least their PostScript RIP), which claim to simulate offset screening, certainly use a screening more resembling the traditional A.M. offset press screening, but this dot screening remains very different from the press and would produce different colors even if it would be the same.

What is a real problem, once more in the field of the Color Proofing and Graphic Industries, is that Product Marketing is using a very vague and unsuitable vocabulary, which darkens reality and masks the true technical and commercial stakes of modern Graphic Industries.
Concerning Color Proofing, the real productivity (expressed in square meters per hour!), the capital investment cost, and yet more important the cost of operation (Price of inks, paper, and maintenance), are much more important for the End User, plus many other basics needs that are not fulfilled yet by the most expensive systems!

At the time of full digital prepress production workflows, it becomes particularly uninteresting to polarize on detail specifications of color proofing, which moreover are not met. In addition, it becomes SO easy to print offset with stochastic screening...which may close all debates!

Last word: In real world, it has always belonged to the printing press to simulate the Customers' color proofs (and NOT the reverse). And today, the appropriate Color Management tools are existing!

 

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