Colour Accuracy of Corporate Colours in Expanded Gamut Print Reproduction

Martin Habekost and Reem El Asaleh, Ryerson University

Expanded gamut printing, as the name implies, expands the gamut of printable colours that can be achieved through a combination of CMYK by adding Orange, Green and Violet (OGV). Through the addition of these additional three colours it is possible to cover almost 95% of the colours that are in the Pantone® colour guide for printing. The benefit of using expanded gamut printing is, that the same inks can stay in the ink fountains of a printing press and only the printing plates need to be changed from job to job. No time consuming ink changes are necessary if a printing press uses the expanded gamut ink set.

The supervisors of this project have seen samples that show that a Pantone® colour printed using the expanded gamut ink set is not as clean and bright looking as when the same Pantone® colour has been printed as a single spot colour.

The exact reproduction of brand identity colours is very important to brand owners. Brand owners allow minimal colour discrepancies of their brand colour(s). Therefore, it is important to achieve the best possible colour reproduction when printing brand colours using the expanded gamut technology. It is the goal of this project to find out how much colour deviation there is when a Pantone® brand is reproduced with expanded gamut technology. Since many companies offer digital workflow solutions for expanded gamut colour separations it is a goal of this project to find out how colour accurate these different workflow solutions are.

For this project 10 -15 brand colours that use a Pantone® colour will be chosen. These brand colours should cover all aspects of the colour wheel. Adobe Photoshop CC 2018 will be used to create a test form and it will be printed with the Heidelberg PM 74 Sheetfed offset press. The test form will be processed for expanded gamut printing with the GMG OpenColor and Esko Equinox expanded gamut premedia workflow solutions that are available for this project. Folding Carton Substrates will be selected for this project as Expanded gamut printing is mostly used with Packaging applications. There will be at least four press runs needed for this project. Since the selected press is a four colour offset press, the press sheet has to be sent twice through the press. This creates an additional challenge for this project. The researchers on this project have consulted with the providers of the premedia workflow solutions in regards to the best colour sequence of the seven colours.

Once the test sheets have been printed the selected colours will be measured for the L*a*b*-colour coordinates and compared to the L*a*b* values of those Pantone® colours provided by Pantone® itself. The colour differences will be recorded in DE2000 values, and the L*a*b*-values will also be evaluated to see if there is a more dominant colour difference in either red-green, blue-yellow or lightness of the printed sample colours.