Demystifing Techkon SpectroDens4 GrayGuide

Techkon SpectroDens4 has integrated our newly revamped GrayGuide function for checking G7® compliance with a total of 11 reference print conditions and 4 different modes when targeting G7® specifications. In this blog, will discuss each of the modes and how they might be helpful in various scenarios.

G7 Absolute
To configure settings under the Techkon GrayGuide feature, navigate to the bottom right corner and hit the Enter button. Once a Custom Reference Print Condition is determined by your G7 Expert, you should be able to find it under Paper Type. We have included all 7 CRPC data sets defined by CGATS21 or ISO 13655, as well as the old GRACoL and SWOP from 2006 and the latest XCMYK 2017 for expanded color printing.

Make sure the Auto Reference and SCCA are both disabled, therefore all measured values will be compared with official G7 target references, or in other words, printing to G7 Absolute

Depending on if you have certain color strips printed (TECHKON GrayGuide Checker, SpotOn! V1/V2, pressSIGN CMYK 4CX or PrintSpec), you can scan or spot read the patches easily. To download the above color strips, please contact: service@techkonusa.com or call (978) 777-1954.

If you are using the spot method, please make a paper white reading to start. Below we are going to demonstrate how we can measure G7 patches using the scan method.

Once TECHKON GrayGuide V2 and CGATS21-2 CRPC6 is selected under the GrayGuide setting, the device screen automatically notifies the user that it is ready to scan the corresponding color strip.

• Place your device aperture on the first patch, in this case the solid black patch, and press and hold the green measurement button to scan across the entire strip and stop on the last patch.
• If the scan is successful, you will see a job evaluation screen as shown below, which indicates what is a passing G7 specification and what needs to be adjusted.

• In the Figure above, the substrate, primaries, overprints and CMY gray balance patches are all passing G7 tolerances but black ink’s avg. ∆L and max ∆Ch are failing. To investigate more details, several spot readings on the HC_k, HR_k & SC_k are suggested.
• Under spot reading, Techkon SpectroDens4 will provide suggestions based on patch type to achieve G7 specification. For example, the figure below indicates press operator needs to increase the density on SC_k patch for a better result.

G7 Relative with TR015
Under some circumstances, if the actual press substrate is slightly different than the proof but still needs to achieve the same CRPC data set, it is possible to maintain the same reference value for primaries and overprints, but with adjusted Neutral Print Density (NPD) and gray balance for G7 gray patches. The benefit of using this mode is not only the primaries and overprints look the same on both press sheet and proof, but also the gray patches will look neutral too.

To activate this mode, please check the Auto Reference option under the GrayGuide setting. If you are using scan method for measurement, steps above remain as is. But if you are using spot method, here are the procedures.

• Select Single Spot Mode under Control Strip and corresponding CRPC. Make sure Auto Reference is enabled.

• Hit the Exit button to return to the measurement screen. Follow display instructions to measure paper white, 300%CMY patch and solid black patch step by step.

• Once all above three patches are measured, the device is ready to measure any G7 patch.
With the measurement of the above three patch types, TECHKON SpectroDens4 will be able to recalculate the densitometric as well as colorimetric aim for G7 gray patches using CGATS/IDEAlliance TR015 – Methodology for Establishing Printing Aims Based on a Shared Near-neutral Gray-scale (Auto Reference on SpectroDens4).

G7 Relative with SCCA
Turn on SCCA if paper 2<=dE<=5

If the actual substrate is different than the reference but still within 5 ∆E00 (as of December, 2017), SpectroDens4 user can choose to turn on the SCCA (Substrate Corrected Colorimetric Aim). With SCCA enabled, the reference values for primaries, overprints and gray patches will be recalculated based on the actual substrate. The benefit is that printers will be able to achieve G7 Relative with more substrate types and maintain a similar print quality.

To enable SCCA, please check the SCCA under the GrayGuide setting screen. Once it is on, the measurement condition at the bottom right corner turns purplish blue indicating reference values will be recalculated using SCCA. If the Control Strip is set to Single Spot mode, device screen also shows “SCCA on” text message when asking for paper white measurement.

Once actual paper is measured, all measurements will be compared to the recalculated reference values.

G7 Relative with SCCA and TR015
When the actual substrate has a dE00 larger than 5, printers are suggested to reconsider which CRPC they should aim to or they can continue to use SCCA plus Auto Reference for current print condition. Due to the large substrate difference, by applying SCCA only could introduce errors to NPD and gray balance. Therefore, it is recommended to use CGATS/IDEAlliance TR015 for calculating new NPD and gray balance colorimetric aims, meanwhile let SCCA take care of primaries and overprints.
To enable both Auto Reference and SCCA, please setup your device according to figures below.