Which RGB working colour space is suitable for colour-consistent work?

In the early days of color spaces Apple and e.g. Photoshop up to version 5.5 set the monitor color space as working color space by default. But it soon became clear that a design office would be working with 10 Macs in 10 different color spaces. A neutral concept was needed.

There are many RGB Colour Spaces around. In the area of print media there are currently primarily three different variants: sRGB, AdobeRGB(1998) and eciRGB_V2.

The sRGB color space is widely used in digital cameras and is the industry leader in the consumer segment. Problem for printing: sRGB is a relatively small color space, and does not cover the color possibilities of modern offset printing systems and digital printers. Since offset printing profiles such as ISOCoated_v2 have a much larger color space, it makes little sense to perform retouching in sRGB.

From our point of view eciRGB_V2, a further development of eciRGB, is optimal. This color space has been specially created for use in the printing sector and offers some strengths:

  • It covers the colors of all modern printing color spaces (offset, gravure, web offset, newspaper), but is not much larger and therefore does not give away any resolution.
  • Equal shades of red, green and blue result in neutral shades of grey
  • Between 0/0/0 and 50/50/50 there is roughly the same distance as between 50/50/50 and 100/100/100.
  • The white is 5000 Kelvin and the gamma is 1.8 Kelvin.

The eciRGB_v2 color space can be downloaded free of charge from the pages of the European Color Initiative (ECI).

The AdobeRGB 1998 color space, which has been widely used by Adobe since Photoshop 5.5 and today in all parts of the Adobe product range, is also well suited for the printing sector, but works with a gamma of 2.2 and is designed for degrees of whiteness from D50 to D65. All common print color spaces can also be well mapped in AdobeRGB 1998. You can find Adobe documentation on this color space here.

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Softproof – opportunity or risk?

Softproof means: The correct color display of a printed product on a monitor. Both a standardized print, e.g. according to process standard offset printing, can be simulated – e.g. a later offset print according to ISOCoatedV2 can be simulated correctly in colour on the screen – and the output on digital terminals such as LFP systems in advertising technology.

From a technical point of view, soft proofs are now well controllable. The monitor technology is advanced enough to provide excellent displays with a high color gamut and consistent illumination even for a few hundred euros. For example, monitors in two branches of a company can be coordinated in such a way that the result displayed on the monitors corresponds exactly to each other at both locations, i.e. one image editor in Hamburg and one in Munich can talk about retouching the same file.

The problem: The fact that the two monitors emit the identical color and light result can be precisely controlled. The fact that the colleague in Hamburg is looking at the foggy Alster lake at a northern window, while the colleague in Munich moved the monitor to a southern window in the direction of the Isar river in sunshine, already shows the problem: The environment variables under which the softproof is viewed are not identical.

It is even more difficult when the soft proof is to be used in the pressroom to coordinate the production run. Many companies such as JUST offer modern solutions that can provide a soft proof directly at the press. However, the problem remains that the soft proof should be considered to be less than 10% away of the brightness of the press. While 2000 lux brightness was previously the standard for printers, JUST now writes: “The comparison of soft proofs on monitors with prints and hard proofs is regulated in accordance with ISO 12646. The light conditions basically correspond to ISO 3664, but the brightness must be adjusted to the limited luminance of the monitor, which ideally is > 120 cd/m². ”

Two scenarios therefore arise at the printing press: Either the printer is “in the light” and can then match the print with a contract proof printed on paper, or it is “in the dark” and can match the print with the soft proof. The difficulty of matching paper and monitor – and these are two completely different and difficult to compare media – is compounded by the difficulty of the printer having to dim the light at the press by up to a factor of 10 to be able to match both a contract proof and a soft proof at the same workstation. From today’s point of view, this does not really seem practicable.

Conclusion: The soft proof is on the advance and will certainly sooner or later displace the classic contract proof from the market for reasons of speed and cost. However, due to the great technical lighting and haptic differences between the monitor and the illuminated sheet of paper, a widespread introduction is still a long way off. After all, anyone who has ever performed a color match on a printing press can imagine that a match to the contract proof on the one hand and to a soft proof monitor on the other hand is difficult to imagine at the same time.  The contract proof will therefore also have to remain the first choice in the near future in order to be able to carry out colour-accurate proofing of the printing result in the pressroom.

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