Matching Colours (Part 1)

November 1, 2012

in Prepress

As part of a recent consultancy project, we were involved in settling some issues with the CMYK breakdown on a brand Pantone colour potentially being printed globally across a wide range of mediums and processes.

This project, as well as some other recent Xcaliba work, has highlighted some of the problems with colour matching .

 

Xcaliba’s involvement in ‘Project D’ came about when a UK advertising company was looking for a CMYK breakdown on a brand colour for a global FMCG product.  The brand colour was specified as Pantone 431C Grey and a US-based agency gave the process colour breakdown as Cyan 65%, Magenta 52%, Yellow 44% and K (black) as 16%.   When the UK agency proofed these breakdowns on their calibrated proofing systems the results were, in their opinion, nowhere close to the product packaging sample; this despite the US-agency saying that the colour looked fine on their proofing systems.  It was at this point that we became involved.

Our first area of investigation was to check the process breakdown against the Pantone colour reference.  We surprisingly found five different suggested CMYK specs for this colour…

  • Pantone Color Bridge (the new Pantone system) C:45 M:45 Y:16 K59
  • Pantone Matching System (PMS – the traditional system) C:11 M:1 Y:0 K:64
  • Indesign & Illustrator C:11 M:1 Y:0 K:61
  • Photoshop C:65 M:52 Y:44 K:16
  • Quark C:45 M:27 Y:17 K:51

In over seventy five years of combined print experience, this was the first time we had found so many different process tint values for the same Pantone colour and seemed to be the best place to start at looking at the core of the colour matching issues.

Greys, as a ‘neutral’ colour, tend to have inherent matching problems in 4 colour process as they are made up of relatively similar values of two or three process colours and it only needs a small variation within one of the colours to create a difference in the final result.  You may have noticed small grey colour areas on print control bars (the blocks of patterns and colours that print on one edge of a printed sheet – as shown in the image above), these are for grey-balance and give the press operator an immediate visual clue if one colour is printing heavier than it should e.g. if the grey-balance looks too warm then the magenta is printing too heavy.

So….why so many different process breakdowns for 431C and was that the route of the matching issue?  After further investigation it became apparent that there can be several routes to achieve the same destination and all of the tint value references did reproduce a fair representation of the desired Pantone colour, although the closeness of each did vary subject to what paper it was being printed on (more of that in Part 2).

The next area to look at was the proofing systems used by the UK and US agencies.  Each were using different digital colour proofing systems (US – ORIS and UK – GMG) but even when the US re-proofed on a GMG system they were still achieving a different and unacceptable result to the UK.  They were however using different colour profiles and this is the key.  Colour profiles are in-built settings that dictate how colours reproduce on an output device such as a digital colour proof.  The UK agency resent their file with their colour profiles included as part of the digital file and hey presto…the colour printed on both sides of the Atlantic using the same tint values and profiles matched the product packaging.

This is a very specific example of a ‘difficult’ grey colour demonstrating issues with various CMYK tint values as well as differences between, and the importance of,  colour profiles.  One thing to be aware of is that although some Pantone colours print very well as a 4 colour process breakdown, there will always be a difference; with certain vibrant colours such as orange producing the greatest differences.

In Matching colours Part 2, we’ll look at the issues with printing the same Pantone colour across various paper-types.  If you have any questions regarding colour matching issues please don’t hesitate to contact us or have a read through one of our earlier blog posts – Setting up artwork files for print.

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