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soft proof

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soft proof (In French épreuve-écran, épreuve virtuelle) representation of images or printed pages on a monitor for test purposes – unlike hardcopy proof (épreuve papier) – in general, and their contract color-proofed reproduction in particular. A soft proof is contract color-proofed if

– the monitor has a greater color space (wide-gamut monitor) than the printing process color space can offer;

– the monitor was subjected to successful hardware calibration and then the representation capability of the printing process color space was examined by the calibration software (validation);

– under these conditions the color values of the ugra/Fogra media wedge or of a similar control means are reproduced correctly (measurable with the monitor pipette for the correct RGB-CIELAB conversion);

– not only the printing inks but also the coloring of the substrate is simulated.

A soft proof at the printing press central control console (soft copy proof-to-press, e.g. K-Flow SMARtt, wobe-team Proof-Server) is a technical challenge, because there the monitor is in the irradiation area of the standard lighting and its brightness must be reduced (dimmed) to that of the monitor without the color rendering index of the standard lighting changing. The necessary interaction between the monitor, the monitor colorimeter and standard illuminant is implemented via USB interfaces (uniform solution: NEC SpectraView, basICColor Discus, Just Normlicht proofStation). Recommended or standardized parameter values and settings for the soft proof at the central control console:

– LCD TFT monitor with IPS panel technology and hardware calibration with as deep data as possible;

– monitor luminance 160 cd/m²;

– monitor white point 5500 K plus chromatic adaptation CAT02 and gamma 1.8 or L*;

– working color space eciRGBv2 (D50/L*);

– regular recalibration and validation;

– standard light D50, illuminance dimmed from 2000 lx to 500 lx (equivalent to 160 cd/m²) in the comparison between monitor image and printed copy;

– after successful approved press sheet (OK sheet) the monitor is no longer the reference, so that the standard light must be readjusted back to 2000 lx.