Spot Colors

  • CMYK and RGB channels are regarded as process colors. All other channels are regarded as spot colors.
  • Process colors are color managed via MX or standard ICC proof profiles. Spot colors are color managed via spot color sets or multicolor ICC profiles.
  • In case of Roland TrueVIS MG series, it is recommended to define the color management of both process and spot colors, including White (a white spot color or the coating channel), in GMG OpenColor. To do so, you will need a project describing all color channels in the image you want to print in GMG OpenColor. GMG OpenColor will then calculate a proof profile specifically for the proof job, containing a color channel for each color channel in the image. For more information, please refer to the GMG OpenColor helpcenter: https://gmgcolor.com/support/help/opencolor/

With an OpenColor license, you can proof spot colors with MXN DeviceLink profiles, enhancing the spot color simulation with printing process and overprint characteristics.

GMG ColorProof tries to map a channel name in a document to a spot color name in a spot color set. The Spot Color Priority defines the order of sequence in which the spot color libraries are searched.

The first exact match is used. If no exact match exists, GMG ColorProof tries to map the channel name to a similar spot color name and uses the "best match". For example, a PANTONE CVC color will be mapped to a PANTONE C color. If the suffix specifying the media type (U = Uncoated, C = Coated, M = Matte) is missing, the spot color will be mapped to the best match color for coated media type (C). For example, a PANTONE CV color will be mapped to a PANTONE C color.

If no "best match" exists either, the job will not be printed. You will need to manually define the mapping in the Manual Job Manager > Image > Color Management > Channels page.

You have full flexibility to remap channels in the Manual Job Manager. You can manually map a spot color channel to a specific color, or you can apply self-defined rules for an automatic channels mapping (see "Alias-Mapping of Color Channels").

The color channels list in the Manual Job Manager (Image > Color Management > Channels) visualizes the printing sequence: The top color is printed first, the next is second, and so on.

The default order is as follows:

  • Coating channel (customizable extra channel for printers with special inks)
  • White spot colors
  • Process colors
  • Spot colors

GMG ColorProof offers you full flexibility in defining the print sequence and overprinting behavior for spot color channels. The overprinting behavior of spot colors from a db3 spot color database can be edited in GMG SpotColor Editor.
The overprinting behavior of custom spot colors (= spot colors you define by tonal values instead of selecting them from a spot color set) can be defined in the Manual Job Manager (Color column > Define Spot Color). For both spot color types, you can define overprint settings.

Spot colors overprinted by process colors (spots above process colors in the Channels list) are always calculated in Multiply Channels mode.

Option Description
Multiply Channels Automatic algorithm developed by GMG for an optimal overprinting behavior. The Multiply Channels mode is used for calculating GMG spot color sets, resulting in translucent spot colors (solidity = 0). This way, the print sequence does not need to be considered. When deactivating this option, you can enter a custom Opacity value for the spot color.
Opacity

When customizing the Opacity, the print sequence of spot and process color channels is very important for the resulting color impression. In most cases, the spot color with the highest opacity should be printed last to achieve the desired opacity level.

Opacity defines the blending of overprinting spot color channels with all underlying channels. For example, if spot A is printed with an opacity of 50% over spot B, spot B shows through spot A with an intensity of 50%. If spot C has an Opacity of 100%, it will knock out all underlying channels. An opacity of 100% can be useful, for example, for simulating very opaque spot colors. If a spot color is printed directly onto the print medium (top channel in the list), the spot color channel is always printed with 100% opacity, regardless of the Opacity value. This is also the case when printing a Coating Channel.

Spot color descriptions in the form of CxF/X-4 spectral data

If you are using a GMG OpenColor proof standard, GMG ColorProof automatically detects CxF/X-4 definitions in the document and converts them into temporary spot color sets (db3 profiles with tints). Color management is processed in the same way as for regular db3 spot color sets. As for other spot colors, you can add a spot color control strip to verify the spot colors. Color channels with CxF definition are marked as such in the Channels list (Manual Job Manager > Image > Color Management > Channels).

You can check the spot color profiles generated from the CxF data under Job > Printer Settings > Spot Color Priority list. Here, you will see the temporary spot color sets. By clicking a set with the right mouse button, you can open the spot color set in GMG SpotColor Editor.

To use this feature, you will need an active connection to GMG OpenColor and a GMG OpenColor project with published dynamic profiling data. Please read the GMG OpenColor documentation for more information.

This feature requires GMG OpenColor version 2.2 or higher.

See also: