TVI curve and calculation in G7

Because G7 field ink values, NPDC curves, gray balance and characterization data are either represented by chromaticity values ​​or based on chromaticity values ​​(even NPDC values ​​are derived from CIEY, not from density measurement) It is problematic to apply the traditional density TVI value to the G7 standard. But sometimes, a contrasting TVI curve is also useful, for example to check a single color version.

To solve this problem, GRACOL 7 and IDEAlink software use CIEXYZ values ​​to obtain TVI instead of the traditional density measurement method. This will change from the previous CMY TVI value, but this can make TVI a truly useful chromaticity standard, and can exclude artificial density measurement in any state (G7 neutral black ink TVI value or curve in theory and density The measurement method is the same).

Other CIE TVI formulas may also be correct, for example, calculated by the â–³ E * ab reflection value, GRACOL hopes that he can become a formal standard, and then apply these formulas.

CIE XYZ TVI formula for G7 and IDEAlink

n = 0 ～ 100%
TVI_c = (paper_X-nc_X) / (paper_X-nc_X) × 100-n
TVI_m = (paper_Y-nm_Y) / (paper_Y-nc_Y) × 100-n
TVI_y = (paper_Z-ny_Z) / (paper_Z-nc_Z) × 100-n
TVI_k = (paper_Y-nk_Y) / (paper_Y-nc_Y) × 100-n

Use traditional TVI density measurement

When using the G7 method, the printer can also use the traditional TVI density method to control the chromaticity. You can use G7 chromaticity target values ​​(NPDC, HR, gray balance, etc.) to calibrate the device. These readings can be used as process control targets for equipment or other media combinations, or for production process records.

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