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Instrument Inspector

Inter- and  Intra-Instrumen agreement?

Different measuring instruments are built in a way that makes measurements of the same sample more or less distinct. We assume that the apparatus of different suppliers measure slightly differently. We also know that the instruments of the same supplier do not give the same results. We understand that individual copies differ from each other. Do we realize, however, that these differences are not only what instrument we measure, but what is surprising in an extreme, not obvious degree depends on what we measure?

Are we aware that deviations can dramatically depend on the surface finish? If we use a Spectrophotometer to measure print - this usually means that we are dealing with two basic elements: the print base and the print itself. Printing is understood as a thin layer, generally semi-transparent paint, toner or ink. Different printing technologies introduce pigments to the substrate in a different way. The physical form of the combination of ink and substrate looks different for offset, inkjet, flexo or digital printing. The printing substrate is a lot of possible substances - it is often paper but mostly surface-modified. This structure viewed enlarged, turns out not to be smooth, has a complicated structure. In addition to paper, we print on various other materials such as plastics, fabrics and even metal.

As if this diversity was still not enough, the surface finish radically changes the environment in which the light measuring the color takes place. Covering the surface with a laminated film that can have the glue layer in it, or varnish the surface - matte or shiny modifies the model of the measurement environment.
Optical and physical phenomena turn out to be difficult to predict, and intuition usually fails.

 

Harmonizing measurements.

ChromaChecker Instrument Inspector allows you to significantly approximate measurements made on the same sample by different instruments. This process is called harmonization. For harmonization to have the expected effectiveness, we created a special target called H-100. It is a target that should be printed on the substrate and in a technology that will be harmonized in the future. If we print on different substrates in diversified technology and with varying finishes of surface - for each of these printing conditions we have to prepare a separate harmonization correction.

 

H-100 Target

In practice, this means that we print H-100 on various substrates and various printing devices. For the harmonization of the proofer, for example, we need to print the H-100 on this machine using proofing paper. On a similar principle, if on an offset press we use UV inks and dispersion varnish by printing on coated paper - this is the printout we need to prepare.

In Instrument Inspector we assumed that each user must indicate the most accurate and stable spectrophotometer - which will be indicated as a master. All other instruments will try to imitate the main one. Now that we have chosen the master instrument, you have the H-100 Target printed in different printing conditions - it has to be measured by the instrument indicated for harmonization and by the Master one.

Print Inspector works by tracks - these describe different printing conditions - it is easy to assign corresponding H-100 Targets that are different for various printing devices, instruments or printing conditions.
Implementation of harmonization for one print medium - when we have finished printouts takes several minutes - this is not a very complicated process. Because we introduce harmonization to improve measurement accuracy - each target has to be measured many times - how much - depends on expectations - but five measurements seem to be a reasonable minimum. Note that multiple measurements show us variances - this is a parameter resulting from the variation of not only measurements - but the uniformity of printing - it happens that solids and tints are not reproduced perfectly - multiple capturing of the same target distinctly reveal this.

 

Implementation

Measurement data assigned to various copies of the H-100 will automatically create baselines for us. The calculations will be made on our own without our participation - the user only needs to assign the right instrument to each track and indicate which of the H-100 targets describes the printing conditions in a given track.

 

Harmonizer — details?

This industry breakthrough technology - (option of Instrument Inspector) enables the ability to normalize the differences between all instruments in your production chain. Select one "Master Instrument" and ChromaChecker will recalculate "on-the-fly" incoming measurement data to match Master Instrument as close as possible. 

All Instruments requiring normalization have to be registered in Instrument Inspector and physical Instrument Inspector targets have to be measured. When setting-up the Harmonizer technology each Instrument has to measure target 10-20 times ( recommended at least +5) to build a Baseline, which creates an average definition of how instrument "measures" color. 

When baselines are created, the system creates correction profiles for each instrument with relationship to Master Instrument. Stored information will be used for future data recalculation.

Each Instrument, including the Master, requires routine verification to ensure that correction profile is up-to-date. This routine gives additional knowledge about current instrument state – if a device is consistent and precise in its measurements.

 

Routine Instrument verification. 

There are a lot of vendor claims on how Instruments are precise and stable. But in the real world instruments are dropped, temperatures vary, optics become dirty (industrial environment is sometimes very polluted, the air in print house may contain a lot of dust) all of which causes instruments to change how they measure color. Real Inter-Instrument Agreement can be far from perfect. Sending Instrument for recertification is expensive, and usually doesn't fix the problem if it is software or application related.

Frequent Instrument verification with Instrument Inspector will document that Instrument is valid and there is no need for sending Instrument for the recertification — checking every week or every month will create records for the audit. ISO 9001 required documentation will be created and at the same time the correction profile is generated.

Typical Inter Instruments comparison shows E-Factor in the range of 1- 2 delta E and much higher in some cases depending on the instrument pair. In most cases Harmonizer can reduce this error by 60%+ for unlike instruments, and even higher for like instruments.

A typical scenario where this becomes critical is when the ICC profile for the proofer was made with iSis or i1IO, and the proof verification is made with Exact or i1Pro. A well-profiled proofer can be 2 E-Factor from the printing aim when measured with the different instrument because two different instruments measure same patches differently. Harmonizer can reduce this problem by 50% or more! In the same way measurements from the handheld device may be very different from press instrument, and Harmonizer will reduce this delta E stack that contributes to overall error in the process. By reducing this error, the printer will have an easier time manufacturing color to meet the customer's expectations which will save time and money due to less waste, and less make ready, and less discussion related to the color product.

 

Case Study

Print Conditions / H-100 Targets

  • Let's imagine that we have a proofer - that uses Proofing Paper (EPP)
  • Dry offset press with UV inks that prints on plastic substrate  (PVC)
  • Mid-size Large Format Printer with Premium High Glossy Photo Paper (EPH)


Instruments

  • Konica Minolta FD-9 — Set as a Master Instrument (very stable, wide spectral range, M0, M1, and M2)
  • Konica Minolta FD-7
  • X-Rite i1Pro 2
  • X-Rite i1Pro 1
  • X-Rite i1IO Pro 2
  • X-Rite eXact Scan