Applications Technical Lead,

Sales and Technical Services.

Graphic Arts & Print Markets

KAYELL AUSTRALIA

https://www.kayellcolour.com.au/

GMG OPENCOLOUR

Profiles with Minimal Data

INTRODUCTION:

Input profiles, output profiles, namespace profiles and abstract profiles. In the world of colour management, profiles are ever prevalent. Still, since the introduction of the ICC profiles in the early 1990’s, there has not been a significant amount of innovation in profiles or their generation methodology. Today the fundamentals of an ICC based colour management system still typically rely upon the two-stage transformations from input to output using a profile connection space in-between.

In our web-publication ‘Profiles 101’ we briefly reviewed the fundamentals of profiles, their anatomy, typical generation and limitations. Today we would like to present a revolutionary innovation in profile generation:

Specifically designed to meet the needs of the packaging industry, GMG OpenColour ensures CMYK and spot colours print exactly the way you want them to. GMG's patented OpenColour technology is unique. It enables accurate proof simulation of the overprinting effects of spot colours using special multichannel profiles. The spectral data calculation includes printing technologies, media types and printing order and its results are so reliable that profile iterations are no longer necessary. (1)

THE PREDICTIVE ENGINE:

At the core of GMG OpenColour’s application are its predictive algorithms, providing the ability to accurately regenerate profiles post changes to media, ink sequence and other key factors without the requirement of reprinting and measuring new characterization charts. Also, it can accurately generate profiles with fewer characterization data than that of traditional proofing methodology.

For accuracy in the generation, key parameters require designation within the application. Then with changes, the project can simply be duplicated, modified and regeneration of both proof and separation profile immediately created.

A NEW WAY TO PROFILE:

Traditional methodology for output profile generation relied upon the printing and measuring of large-scale characterization charts, typically, with 1,000+ patches. For example, the IT8/7-4 has a total of 1617 patches, and an ECI2002 chart has 1485 patches. These charts would contain CMYK solid and tonal patches, as well as combination patches for analysing overprint behaviour.

Due to the size of these charts allocation of press time would be required, stopping production. Also, with the cost of plates and material, this process often sums to be a costly operation. However, the most significant shortcoming of traditional profile generation is the reliance on the constant state of the output device. The profile is specific to one particular device, one substrate, one ink-set and the parameters as set in the RIP. Once any of these change the profile is no longer accurate, and recreation of the profile is necessary.  

With GMG OpenColour these limitations are no longer. Not only is the reprinting and measurement of charts after process change not required but also the amount of characterization data required for accurate profile generation is minuscule in comparison. GMG OpenColour offers a measurement capability for custom patches. Previously customers would require a specific test chart to create a colour profile, GMG OpenColour enables the measurement of full-tone patches from a print control strip, or even solid patches and tint patches on the running printed sheet and to create a profile from the captured spectral data, something no other profiling tool can achieve. (2)

PUT TO THE TEST:

To verify the accuracy of GMG OpenColour our team at Kayell Australia conducted some independent tests of our own. We organized press time on both an offset Roland 700 sheetfed press and a flexographic Comexi F2 web press. The premise was simple, compare a proof profile generated using the traditional methodology to proof profiles generated with GMG OpenColour. Each of the proof profiles would then be measured against target values as printed on the target output process.

For the complete detailed report on both tests, visit:

www.kayellcolour.com.au

OFFSET TEST

PRESS: MANROLAND700

SUBSTRATE: BOARD, MACHINE FINISHED COATED

For our offset test on the Roland 700, we had four pieces sent through the RIP then plated and printed. An ECI2002 test chart, a GMG OpenColour 70 patch mini-strip, a GMG OpenColour 21 patch mini-strip and a GMG 4 colour test page. The ECI2002 chart has a total of 1485 patches and would be used to create a traditional method proof profile, both GMG OpenColour mini-strips would be used to create two separate GMG OpenColour proof profiles and the GMG 4 colour test page, which included a 72 patch Fogra media wedge, to be used as our target. 

Measuring the ECI2002 chart and the two OpenColour min-strips three separate proof profiles were generated. (note: we also iterated the ECI2002 profile three times) We then printed the GMG 4 colour test page using each profile via GMG Colour Proof, outputting to an EPSON 4900. With our three separate GMG 4 colour test page proofs, it was time to measure.

For measurement, we used an Xrite eXact advanced spectrophotometer, over a Munsell backing sheet and the colour difference formula of CIE deltaE2000. (For full print, proof and measurement specifications used, see attached excel document at www.kayellcolour.com.au) Using the compare function in the eXact, we set the target as the first patch of the Fogra media wedge on GMG 4 colour test page printed by the Roland 700 and then measured the same patch for each of the proofs, noting the delta difference and deltaE. This process was repeated for all 72 patches on each of the three proofs.

FLEXO TEST

PRESS: COMEXI F2

SUBSTRATE: FILM, LAMINATED

For our flexographic test on the Comexi F2 the same process was followed as on the Roland 700, however, due to press restrictions, three modifications were required. First to generate the traditional method proof profile a GMG Flexov2 chart was used (1472 patches). Secondly, only one GMG OpenColour proof profile was generated, this was a 70 patch mini-strip. Finally, the first 11 patches of an ECI Grey control strip were used as our target.

THE RESULTS:

The results are nothing short of impressive.

In our offset test the proof created with the GMG OpenColour 70 patch profile measured with overall better results than the proof created with full ECI2002 1485 patch profile. Out of the total 72 patches of the Fogra media wedge compared, the GMG OpenColour 70 patch proof had 30/72 patches with the lowest dE. The ECI2002 proof had 26/72, and the GMG 21 Patch proof had 16/72. The GMG OpenColour 70 patch proof had an overall patch average of '1.47'dE, compared to the ECI2002 proof average of '1.75'dE giving an overall lower dE average of '.28' than the ECI2002 chart. Moreover, with 1464 fewer patches than the ECI2002 profile the 21 patch GMG OpenColour proof had a higher dE average of only '0.19'.

In our flexographic test, the results were equally as impressive.

Out of the total 11 patches of the ECI Grey control strip measured the GMG OpenColour 70 patch proof had 9/11 patches with the lowest dE, compared to 2/11 on the Flexov2 chart. The GMG OpenColour 70 patch proof had an overall patch average of '2.03'dE, compared to the Flexov2 proof average of ‘2.93’dE, giving an overall lower dE average of '.90' than that of the Flexov2 profile.

In both of our tests, 2/3 of the proofs created with a GMG OpenColour profile had an average lower dE than that of proofs created using traditional methods, with the third having only an average ‘0.20’ higher dE. Considering that the GMG OpenColour mini-strips have around 1450 fewer patches and are 1/13th of size comparing to the traditional chart, these results indeed are remarkable. 

THE SPECTRAL DIFFERENCE:

To understand how a profile with less than 5% of the patches of a traditional characterization chart can create a proof equally as accurate we must look at the differences in the profile creation process. The first step in all profile generation is the measurement of the printed characterization charts. Using a spectrophotometer each patch is measured, the device capturing the patches spectral data as a spectral curve. The spectral curve describes the amount of reflected light from a colour which is illuminated by a standardized light source. In traditional profile generation applications, this spectral curve then is transformed into a profile connection space (PCS). For example, Spectral to XYZ then to LAB. These transformations lead to data loss and inaccuracies in the generated profile.

GMG OpenColour is different. Rather than transforming into a profile connection space and using the LAB values to generate the profile GMG OpenColour uses the raw spectral data for a precise colour calculation.

The development of the prediction model in GMG OpenColour started in 2000. GMG measured thousands of printing sheets from each conventional printing process; flexo, offset and gravure to understand the spectral curve behaviour when switching conditions on the press; such as ink sequence, substrate and the effect of different varnishes. Investing in ten years of research, GMG was able to understand these effects on spectral behaviour and produce the physical, mathematical and software model used at OpenColour core. The first version of GMG OpenColour showcased at DRUPA in 2012, and the worldwide patent was published in 2013, securing GMG as being the only company in the world with a spectral profiling solution.

LIMITATIONS:

As with any solution, there are limitations. In GMG OpenColour if producing a profile for a digital press, the mini-strip cannot be used, this is due to the variation and differences between digital press. For an accurate digital press profile, full characterization charts are required. These charts have a similar patch count as that of an ECI2002 or FlexoV2 chart. Secondly, with the addition of inks on a press (e.g: CMYKOVG) full characterization charts also are required, this is to ensure the accurate prediction of how the additional inks affect the overprint behaviour.  

CONCLUSION:

Described by experts as “the most incredible tool of the last 20 years” (3) and winning the 2017 EDP award for the best colour management solution GMG OpenColour is quickly becoming known as the most accurate profiling solution available in the market, furthering GMG position as an industry leading developer.

Did you know accurate profile generation is only one element of GMG OpenColour? It also has the capability of generating separation profiles, enabling the reseparation of artwork between colour spaces. However, that in itself is a whole other article!

REFERENCES:

1. GMG Gmbh & Co; (Referenced:06/2018) https://www.gmgcolor.com/products/opencolor/

2. GMG Gmbh & Co; (Referenced:06/2018) https://www.gmgcolor.com/products/opencolor/

3. GMG Gmbh & Co; (Referenced:06/2018) https://www.gmgcolor.com/products/opencolor/