Black tint preservation
This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.
Black tint preservation preserves black values for all black tints. It has two modes: it can either preserve the original black value, or it can preserve the relative luminosity of the black.
The luminosity of the black tint can only be preserved for a given color transform if that transform is composed of two ICC profiles for source and destination. The preserved value is discovered by performing a reverse lookup through the device to PCS transform of the ICC destination profile. If converting color to the output device, and setreproduction is configured with NextDevice transforms, this restriction applies only to the final NextDevice transform. If it is not possible to preserve the black luminance, the original black value is used in the output.
The device to PCS transform of an ICC destination profile is not normally used by CMMs, but the ICC specification requires it to give a good round trip with the PCS to device transform of the same profile for a given rendering intent.
If 100% black preservation is enabled at the same time as black tint preservation, 100% black preservation applies to 100% black values, and black tint preservation applies to all other values.
Black tint preservation cannot be applied to output devices with a color space of /DeviceRGB or /DeviceGray, that is, the color space is restricted to /DeviceCMYK or a /DeviceN space with a black component.
Black tint preservation is enabled with the BlackTint setinterceptcolorspace key:
<< /BlackTint false >> setinterceptcolorspace
The sense of the Boolean is the same as the Black key. This sense could be regarded as “color management does not apply to black tint color values”.
As stated above, the default mode of black tint preservation is to preserve luminance. If it is desired to preserve the original black values, this can be done by disabling BlackTintLuminance using:
<< /BlackTintLuminance false >> setinterceptcolorspace