Overview of the Workflow

Baseline: Stabilize printer, set ink limits.

Calibrate CMYK: Print CC84 or P2P, measure, generate G7 curves, apply, and verify.

Calibrate OGV: Print OGV ramps, measure, generate SCTV curves, and apply.

Characterize: Print a multi-channel (ECG) target.

Profile: Measure the ECG target and build the final 7-color ICC profile.

The Extended Color Gamut (ECG)  process involves two distinct but related standards:

G7® is used to calibrate the CMYK components to achieve a shared neutral appearance and tonality.  This creates the "gray skeleton" of your print.

SCTV (Spot Color Tone Value) is used to calibrate the OGV (Orange, Green, Violet) or other spot colorants. This ensures their tonal ramps are visually uniform.

You must perform the G7 calibration first, as it establishes the fundamental behavior of the press or printer. 

What You'll Need: The Toolkit

Hardware and Software

A high-quality spectrophotometer (e.g., X-Rite i1Pro series, Konica Minolta FD series, Barbieri Spectro LFP). It must be capable of M1 measurement conditions for modern standards.

The printing device (offset press, digital press, wide-format inkjet, etc.) with a workflow that can manage ECG.

RIP/DFE Software: A modern RIP (Raster Image Processor) that supports G7 and SCTV calibration (e.g., Caldera, Onyx, Fiery, Esko, PrintFactory). ChromaChecker wil report on these individual processes to ensure stability and consistency along with the alignment of multiple printing devices.

Analysis & Curve Creation Software: Software that can analyze measurement data and generate G7 and SCTV correction curves. This is often built into the RIP, using ChromaChecker G7 Curve or standalone products can be used as complimentary to ChromaChecker. ChromaChecker is an open system and works well in varying workflows.

Targets:

G7 Calibration Target: Using the Idealliance P2P  target is commonly used for G7 calibration, but can be streamlined using a CC84 target in the production process. This approach is more efficient and will reduce the interruption to production as the CC84 can is a more efficient target. G7 is best used for process control, not production control. E-Factor or Delta E is the best metric for productivity and salability of print documents when it comes to color matching.

SCTV Calibration Target: A target with tint ramps (0-100%) for each of your single OGV colorants. Most RIPs can generate these and can also be easily created in ChromaChecker Capture Inspector.

Verification Target: A G7 Grayscale Control Strip or a full characterization target like the IT8.7/4 or IT8.7/5 are all available in ChromaChecker. The can also be used for G7 verification with ChromaChecker as a serice to achieve G7 verification.

Part 1: Calibrating CMYK using G7

The goal of G7 is not to match a specific color proof; ChromaChecker E-Factor is best used for this purpose, but to ensure that the printer produces a visually neutral gray balance and a standardized tonal response. ChromaChecker will also best check uniformity or variation which is important when evaluating curves.

Step 1: Initial Printer Setup & Baseline

Before you start, ensure your printer is in a stable, repeatable state. This is completed using Print Inspector and measuring your control strip of choice.

Check Printer Health: Run nozzle checks, perform print head alignment, and ensure all hardware is functioning correctly.

Set Ink Limits: If not already done, you must establish the maximum amount of each ink (C, M, Y, K) and the total ink limit (TAC) the substrate can handle without bleeding, mottling, or unacceptable drying times. This is a prerequisite for any calibration. Substrate can be evaluated using ChromaChecker Substrate Inspector and tracked in Print Inspector. SCCA calculator can be used for generated a new ICC Profile target.

Linearization (if required): Perform a basic linearization to create a starting point. This is not necessary if an existing ICC Profile or Curve is identified in the workflow. This ensures that a 50% dot in the file results in roughly a 50% dot on paper. Most RIPs have a dedicated module for this. ChromaChecker can iterate curves eliminating the need for dedicated print runs. 

Step 2: Print the G7 Calibration Target

If you do not know what ICC Profile is in the workflow, Print the CC84 or P2P target Turning OFF all color management. You need to print the raw, uncorrected device values. Note: this is the configuration that can be used with ChromaChecker Color Match functionality when creating Lookup Tables (LUTs)

Let the print dry/cure completely as it would in a normal production run.

Step 3: Measure the Target

Using your spectrophotometer and measurement software:

Set the measurement condition based on your instrument capabilities, M1 (D50) is a common selection for substrates with Optical Brightening Agents (OBAs).

Measure all the patches on the target. 

Step 4: Analyze the Data & Generate Correction Curves

ChromaChecker Analyze Gray Balance: It looks at the CMY neutral tint patches (column 4 on the P2P) and the K-only tint patches (column 5).

Compare to G7 Aims: It compares your measured data against the official G7 NPDC (Neutral Print Density Curve) and the specified gray balance (a* and b* values).

Generate Curves: The software calculates the necessary adjustments for each channel (C, M, Y, and K) to force your printer's output to match the G7 aims. The output is typically a format to your RIP, using an open standard or values you can enter in your workflow.

Step 5: Apply the G7 Curves in the RILoad the newly generated correction curves into the calibration or re-linearization section of your RIP software. These curves will now intercept all CMYK data and modify it before it's sent to the printer.

Step 6: Verification

You are not done until you verify!

Print a Verification Target: Print the CC84 or Idealliance G7 Grayscale Control Strip or a full IT8.7/4 target with the G7 curves active. Use ChromaChecker Print Inspector, G7 Curve Inspector, ICC Profile Inspector and Substrate Inspector.

Measure and Analyze: Measure the gray balance patches on the new print. and  track using Print Inspector. 

Check the Results: ChromaChecker will tell you if you have achieved G7 Grayscale Compliance. It must pass specific tolerances for ΔL* (lightness difference) and ΔCh (chroma difference) across the gray ramp. 

If you pass, your CMYK system is now G7 calibrated.

Part 2: Calibrating OGV Colorants via SCTV

SCTV (ISO 20654) was developed because traditional dot gain (TVI) is based on density and doesn't work for non-CMYK inks. SCTV is based on CIELAB colorimetric measurements and produces a visually uniform tonal scale for any color.

Step 1: Ensure G7 is Complete

Your G7 calibration must be finished, verified, and active in the RIP. The CMYK foundation must be stable before you add the OGV colorants.

Step 2: Print the SCTV Tonal Ramps

Using your RIP, generate and print a target that contains single-channel tint ramps for your extended gamut inks. You can also use ChromaChecker Capture Inspector for creating control strips that contain Channels.

One ramp for 100% Orange down to 0% (e.g., in 10% steps).

One ramp for 100% Green down to 0%.

One ramp for 100% Violet down to 0%.

 Print this target with the G7 curves active but with no other color management applied to the OGV channels.

Step 3: Measure the OGV Ramps

Using your spectrophotometer (in assigned mode ie. M1), measure the CIELAB values of every patch for each of the O, G, and V ramps. You will have a set of Lab measurements for the 10%, 20%, 30%... tints of each ink.

Step 4: Calculate SCTV and Generate Curves

Your RIP or analysis software will perform the SCTV calculation:

SCTV Calculation: For each tint patch, the software uses a formula that compares its Lab value to the Lab value of the substrate (0% ink) and the solid ink (100% ink). This yields the SCTV value for that tint.

Generate Curves: The software compares the calculated SCTV values to a desired linear tonal response (i.e., a 50% input should produce a 50% SCTV value). It then generates correction curves for O, G, and V to achieve this linear SCTV response.

Step 5: Apply the OGV Curves in the RIP

Load these new OGV correction curves into your RIP, alongside the existing G7 curves for CMYK.

Putting It All Together: Final ECG Characterization

Now that your device is fully calibrated (G7 for CMYK, SCTV for OGV), it is in a known, stable, and repeatable state. This can be doumented in ChromaChecker Print Inspector. The final step is to characterize this state by creating a multi-channel ICC profile.

Print a 7-Color Target: Print a large gamut ECG characterization target, such as the IT8.7/5, which contains thousands of patches including CMYK, OGV, and various overprints (e.g., Orange + Cyan, Magenta + Green).

Measure the Target: Use your spectrophotometer to measure all the patches.

Build the ICC Profile: Use profiling software (like X-Rite i1Profiler, basICColor, or a module in your RIP) to generate a 7-color (CMYKOGV) ICC profile from the measurement data.

This final ICC profile is what you will use in your workflow (e.g., in Adobe Photoshop or in the RIP's color management engine) to accurately convert RGB or CMYK source files into your printer's 7-color gamut. You will use this in ChromaChecker as the baseline for the Printer and target for consistency and stability of the printer. ChromaChecker QuickCheck and Color Match functionality uses this provide accurate spot color matching. Color Inspector uses this file to generate virtual printing to evaluate spot color libraries. 

Overview of the Workflow

Baseline: Stabilize printer, set ink limits.

Calibrate CMYK: Print CC84 or P2P, measure, generate G7 curves, apply, and verify.

Calibrate OGV: Print OGV ramps, measure, generate SCTV curves, and apply.

Characterize: Print a multi-channel (ECG) target.

Profile: Measure the ECG target and build the final 7-color ICC profile.

ChromaChecker will ensure not only that your grays are neutral and consistent (thanks to G7), but also that your spot colors have smooth, predictable tonal gradations (thanks to SCTV), leading to high-quality, repeatable expanded gamut printing.