Printing Color Digital Inspection: (4) On-Screen Inspection vs. Physical Sample Inspection

Release Date： 2024-05-27 15:56:40 View Count： 0

Screen inspection refers to the process for clients equipped with screen soft proofing systems, generally requiring professional-grade monitors such as EIZO's CG series, paired with specialized color calibration software and measuring instruments for screen calibration and assessment. The process begins with color correction of the screen using software like ColorNavigator or basicolor, followed by evaluating the calibration results against a specified ICC profile, culminating in a report detailing average and maximum color differences, among other parameters. Compliance with ISO 12646 can provide a comprehensive assessment.

Physical sample inspection encompasses digital proofing, digital printing, and conventional printing, representing the most mainstream approach. Standards and tolerances vary, ranging from ISO 12647-2 to ISO 12647-9. Notably, the China Academy of Printing Technology's C9 evaluation allows for the choice between screen and digital proofs.

Both short and long color bar inspections for sheet color detection rely on color bars. By examining the elements within color bars, indirect monitoring of the print sheet's color is achieved. The length and specifications of the color bars, along with the printing format, measuring instruments, software used, and monitoring standards, differ.

In one scenario, short color bars consist of solid CMYK, trap, CMYK halftone, gray balance, and any spot colors used in the document, placed outside the graphic area of the sheet in one to three instances, with each bar's length usually limited to 25cm and each color patch width exceeding 7mm to accommodate manual measurement with devices like X-Rite i1. GMI certification and inspections for packaging printing follow this method. For digital proofing, ISO 12647-7 specifies the required color block types and elements, with control strips from Fogra and Idealliance being widely adopted. updated versions of these strips consist of three rows with 72 and 84 patches respectively.

Alternatively, long color bars matching the sheet's width are added at the sheet's head or tail. Their composition mirrors short color bars but arranged differently, with each ink zone requiring CMYK solids to monitor density and hue. Multiple zones form a complete strip, which repeats across the sheet length, though sometimes it varies throughout. Given the common quarter or half-sheet formats, track-mounted automated scanners are necessary for measurements, typical for outsourced book and journal orders. However, extensive sample sheets for toy brands like Hasbro also employ scanned long color bars.

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