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International Color Standards, Part 2: Looking at Standards and their Meanings

(November 2007) posted on Mon Dec 03, 2007

Wading through all of the international standards for graphics printing can be a daunting task. Ruff's assessment of their purpose can help you better understand their value.


By Mike Ruff

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The dash after the standard number indicates the process to which the standard refers. ISO 2846-1 is offset ink. ISO 2846-4 is screen-printing inks. SWOP values are measurements from a printed standard that SWOP has produced targeting these colors. GRACoL refers to ISO 2846-1 in GRACoL 7 and also in the G7 calibration methodology. SWOP says, “Proofing inks must be used that conform in color to ISO 2846-1, Graphic Technology Specifications for Colour and Transparency of Printing Ink Sets-Part1: Sheet-Fed and Heat-Set Web Offset Lithographic Printing.” However, SWOP supplies ink samples that are called High and Low references. This is a good system, because colors can be measured and matched while taking out the possibility of instrumentation differences.

 

 

ISO 12647

ISO 12647 contains print specifications (Tables 2A and 2B).

A dash and a number follow the specifications for print. Sheet Fed Litho is 12647-2, Screen Printing is 12647-5, and Proofing is 12647-7. What I want you to see here is that solid ink is very similar, except when the substrate changes. Then Gamut Color reference in the screen-printing ink is based on a printer’s choice to use a high- or low-density ink. Personally, I think if you are going to have a standard, have a standard and quit offering choices. This does not affect the usefulness of the standard. It just increases the confusion of what is right. It is obsolete thinking to say that we need a different appearance standard for different line counts and paper quality and then add the confusion of density choices. We can eliminate this issue by adjusting tonal values to make different line counts appear as the same color by simply adjusting the TVI (tonal value increase or dot gain) through good design and color-management capabilities available.

If the solid colors are the same, our job of standardizing appearance gets even easier. We can very easily standardize dot-color appearance today. In other words, I believe the standards for the different appearances are outdated, but the standardization of color is set and should stay the same. G7 fixed this problem and has now challenged decades of assuming that we can’t adjust dot gain (TVI). G7 does not ignore international standards, but makes them work a lot better by eliminating the problems associated with having so many choices of appearance.

 

SWOP


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