(v13) Wide gamut CMYK exchange space
This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP
This is the recommended method for color managing an XG device.
This method is essentially an emulation configuration that uses a wide gamut CMYK virtual device as the exchange/emulation space; it was briefly mentioned in, (v13) N-Color ICC profiles . The goal of this method is to simplify the color management effort required for different papers and screenings, as far as possible. To that end, specialized N-color profiling methods and tools should be used by the OEM to create a single DeviceLink profile that converts from a standard wide gamut CMYK virtual device to the XG device.
CMYK profiles for individual media stock and screenings can be created using standard CMYK tools, possibly by knowledgeable end users. This is the recommended configuration for this workflow:
<<
/DeviceCMYK [ /ICCBased (iccprofiles/SWOP.icc) (r) file ]
/DeviceRGB [ /ICCBased (iccprofiles/sRGB.icc) (r) file ]
/OverprintPreview /SpotsOnly
>> setinterceptcolorspace
<<
/Profile (iccprofiles/WideCMYK.icc) (r) file
/NextDevice <<
/InputColorSpace
[ /ICC(iccprofiles/StandardWide-CMYKOG.icc) (r) file ]
/NextDevice <<
/InputColorSpace [
/CMM (ink-limiting-CMYKOG-240)
/[ /DeviceN [/Cyan /Magenta /Yellow /Black /Orange /Green]
/DeviceCMYK {pop pop}]
/[ /DeviceN [/Cyan /Magenta /Yellow /Black /Orange /Green]
/DeviceCMYK {pop pop}]
]
>>
>>
>> setreproduction
where StandardWide-CMYKOG.icc is the N-color DeviceLink created for the standard wide gamut CMYK virtual device and CMYKOG device pair.
The CMYKOG device may also be configured to use only CMYKO or CMYKG colorants. New N-color profiles should be created for each colorant combination.
Each media stock and/or screening normally requires its own profile. Ideally this would mean its own N-color profile. It may be possible to simplify this in some cases by sharing N-color profiles and making separate CMYK profiles instead.
The standard wide gamut CMYK profile should have a sufficiently large gamut that it encompasses as much of the XG gamut as possible without being too large. The ICC has created PRMG_v2.0.1_MR.icc , that is intended for this purpose. It is available for free download from [ICC_exchange].
In our experience an ink limiting transform will be required to avoid expensive machine failures. The ink limiting could be built into the N-color profile, or as illustrated, it could be via an additional /NextDevice. In the example it’s implemented in the (ink-limiting-CMYKOG-240) CMM custom color space, which accepts the six device colorants for input and output. It is probably desirable to offer a small number of different levels of ink limiting for use with different classes of media.
Creating the CMYK profiles for use in conjunction with the N-color DeviceLink is discussed in the following section.
Creating CMYK Profiles for the XG Device
Once an N-color DeviceLink profile has been created for an XG device, CMYK profiles should be created for particular media stock and screenings using standard tools. During this profile creation process, the standard wide gamut CMYK virtual device is the effective device, so the color management downstream of the virtual device should be configured as it will be in real use. From the above example, this is the configuration that should be in effect:
<<
/DeviceCMYK null
/DeviceRGB null
/DeviceGray null
>> setinterceptcolorspace
<<
/Profile <<
/Default (%os%/iccprofiles/WideCMYK.icc) (r) file
>>
/NextDevice <<
/InputColorSpace
[ /ICCBased (iccprofiles/StandardWide-CMYKOG.icc) (r) file ]
/NextDevice <<
/InputColorSpace [
/CMM (ink-limiting-CMYKOG-240)
[ /DeviceN [/Cyan /Magenta /Yellow /Black /Orange /Green]
/DeviceCMYK {pop pop}]
[ DeviceN [/Cyan /Magenta /Yellow /Black /Orange /Green]
/DeviceCMYK {pop pop}]
]
>>
>>
>> setreproduction
<<>> setpagedevice
The call to setinterceptcolorspace ensures that device-dependent color spaces are not intercepted. In turn, that means that the CMYK profile in the setreproduction call is not used for the test patches that will be measured when making the CMYK profile. The rest of the call to setreproduction should exactly match the configuration used in production.
When making profiles for new substrates, you will probably need to select either an appropriate CMYK to XG device-link, or ink-limiting profile based on the maximum total area coverage (TAC) that can be used with that substrate.