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Understanding OverprintPreview


This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.

When graphical objects are overprinted, the result is normally device dependent because the foreground and background colors are blended in device space. If the job is output on a device that requires no color management, and it directly supports all named colorants used by the job, the resulting output is as expected by the designer. As a corollary, if color management is used, or if named colorants require conversion to process colorants, the effects of overprinting must be ignored or simulated.

Setting OverprintPreview is only useful with composite jobs. Unexpected results may occur if it is used for pre-separated jobs.

OverprintPreview may take one of three values. For most color-managed workflows, we recommend that you use /SpotsOnly.  The value of false is suitable for most “no color management” workflows.  Where Harlequin VariData (HVD) is in use we recommend that you use /SpotsOnly or true.

false

(Boolean false) This is the default before v14.1.

  • A simple interpretation of the Postscript and PDF specifications is applied; requests for spot separations that are not available on the output device result in immediate replacement with their alternate color space. This means that spot color overprints may be ignored, resulting in spot objects knocking out unexpectedly.

  • The effects of overprinting and/or transparency may be non-colorimetric. Color-managed CMYK non-zero overprinting is emulated using a technique similar to the Darken PDF blend mode (that is, for each colorant that would be overprinted without color management, use the darkest of the foreground and background). The result is not colorimetric, but it usually gives a plausible approximation of the overprint.

  • Do not use the value false if NextDevice transforms are in setreproduction.

  • The effects of overprinting may be unexpected where Harlequin VariData (HVD) is in use.

/SpotsOnly

(Name SpotsOnly) From v14.1 this is the default.

  • Use when spot color overprints must be emulated.

  • Use when the job contains at least one spot color and there is at least one NextDevice transform in setreproduction. Overprints are then merged before this transform.

CMYK overprints will be the handled the same as for the false value.

true

(Boolean true)

  • Use this value instead of SpotsOnly if you require colorimetric CMYK overprints.

  • Spot colors are handled the same as SpotsOnly, but non-CMYK colors may lose some fidelity compared with SpotsOnly.

OverprintPreview may have an effect on performance for some jobs.