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Separation settings

Roland Schibel
  • Updated

Separation settings define how colors are converted between different color spaces when creating separation profiles. Depending on the selected separation type, different options are available.

Multicolor → Multicolor

Parameter Description
Total Area Coverage (TAC) Defines the maximum total ink limit (sum of CMYK) as a percentage. Lower values can help prevent excessive ink coverage or drying problems during printing. Default: 330 %
Ink Saving (CMYK)

Select a preset to automatically control gray component replacement (GCR) and ink reduction, or fine-tune all values manually.
 

  • Light: Applies minimal ink saving with focus on color accuracy. Sets the GCR level to 50 %.
  • Medium (Default): Applies a balanced setting between ink saving and color stability. Recommended for most projects. Sets the GCR level to 75 %.
  • Strong: Applies maximum ink saving; may slightly reduce color accuracy. Sets the GCR level to 100 %.
  • Custom: Adjust the ink saving level manually instead of using predefined values.
GCR Level (CMYK) When an Ink Saving preset (Light, Medium, or Strong) is selected, this value is set automatically and cannot be changed. To fine-tune the amount of Black used for gray component replacement (GCR), select Custom under Ink Saving, which makes the slider editable.

Increase the GCR level to replace more CMY with Black in neutral areas, reducing total ink and making the print result less sensitive to process variations. Set the value to 0 to disable additional Black generation. This control affects only CMYK inks, not any additional inks in the configuration.
Black Start (CMYK) Defines the percentage at which Black starts being used in the CMYK channels.
Increase this value to delay Black generation and increase CMY usage in light and mid tones. This setting affects only CMYK inks, not any additional inks in the configuration. Default: 0 %
Allow Additional Inks in Overprints When enabled, additional inks may be used in overprints if this improves color accuracy. This is especially useful when the resulting color is significantly different from the individual colors.
For example, if a blue spot color is defined to avoid Green, the system may still use a limited amount of Green in such overprints. The amount added depends on the single-color limits and is adjusted automatically to ensure smooth gradations.
Gray Adjustment to Target Media Defines how strongly the paper tint of the target medium affects the printed colors.
This is relevant when the target substrate has a different white point than the document’s output intent and mainly affects gray balance and light colors.
Move the slider to the left to preserve the original color appearance and minimize the influence of the paper tint. Move it to the right to adapt the design more strongly to the target paper color, especially in highlights and gray areas. Default: 30 %
Black Point Compensation Controls how much shadow detail is preserved by adjusting black point compensation (BPC).
Higher values minimize clipping in dark areas and preserve detail but may slightly reduce saturation. Lower values deepen blacks and increase saturation but can lead to some loss of detail.
Default: 100 %
We recommend using a high BPC value for CMYK-to-CMYK separations of image data and a low value for packaging printed on coated media.
Gamut Expansion Off by default (0%). Move the slider right to exploit more of the printer’s available color space while keeping gray balance unchanged.
This only has a visible effect when the target color space is substantially larger than the source.  Please note that higher values can noticeably change color appearance, so review proof results carefully before production.
For maximum effect on printers with extended ink sets, also enable Allow Additional Inks in Overprints.


RGB / CMYK → CMYK

Parameter Description
Total Area Coverage (TAC) Defines the maximum total ink limit (sum of CMYK) as a percentage. Default: 330 %
Decrease the value in case of excessive ink coverage, slow drying, or print defects such as mottling or set-off, especially on absorbent or uncoated substrates. Increase the value if dark areas appear dull or lack depth and the printer and substrate can handle higher ink loads without causing drying or stability issues.
Rendering Intent

Select a rendering intent to determine how in-gamut and out-of-gamut colors are handled during conversion.
 

  • Auto-Optimization (Default): Recommended for most requirements. This hybrid mode analyzes the differences between color spaces and automatically selects the best fitting calculation parameters across rendering strategies, keeping colors mostly relative while applying perceptual adjustments to out-of-gamut colors to preserve a natural overall appearance.
  • Best Visual Impression – Perceptual: Ideal for RGB-to-CMYK. Preserves the overall visual impression of the source image by maintaining color balance, saturation, and detail within the target gamut. 
  • Best Color Accuracy – Relative Colorimetric: Only available for CMYK-to-CMYK. Optimized for maximum color accuracy between very similar printing conditions, including white point adaptation. In-gamut colors are reproduced precisely, while out-of-gamut colors are clipped to the target gamut. 
  • No Gamut Mapping – Absolute Colorimetric: Ideal if exact colorimetric reproduction is required. In-gamut colors are reproduced accurately without perceptual adjustments, while colors outside the target gamut are clipped and the source white point is preserved. Please note that without gamut mapping, some source colors may not be reproducible in the target color space.
Separation Mode

Select how to handle the black channel when creating a separation profile.
 

  • New Separation: Creates a new black generation across the entire color space. It rebuilds the K channel for a consistent black structure in all tones.
  • Keep Black Separation: Keeps the existing black channel and key axis across the color space. Areas without black remain unchanged, preserving the original K structure.
Keep Color Pure (Default) Keep this selected to automatically clean up colors that are only slightly contaminated by other inks. Recommended for most projects to achieve cleaner, more saturated results.
Keep pure (No ΔE Limit) Enable this to purify all colors, even if this causes a higher deviation from the characterization. Solid colors remain pure, but their tone value might slightly decrease (for example, 100 % may be separated to 98 %) unless you also enable Keep Pure Solids (CMY). 
Keep pure Solids (CMY) Enable this to keep 100 % Cyan, Magenta, and Yellow solids, as well as CM, CY, and MY overprints, completely pure. This prevents these colors from being supplemented or replaced by other inks. Overprints with Black are excluded unless Keep Pure Solids (Overprints with Black) is also enabled.
Keep pure Solids (Overprints with Black) Only available when Keep Pure Solids (CMY) is enabled. Enable this to keep 100 % Cyan, Magenta, and Yellow solids that overprint with Black completely pure.
Pure Black (Default)

Defines how strictly black purity is preserved in the separation.
This setting affects all tones built mainly from black ink. The dropdown controls whether small CMY corrections are allowed along the black axis to improve visual neutrality.

  • Low: Allows CMY corrections that maintain visually neutral tones and smooth gradients. Recommended when appearance and tone transitions are more important than absolute channel purity.
  • Medium (Default): Preserves black purity while allowing minor CMY corrections for visual accuracy. Recommended for most projects as a balanced setting between channel purity and neutral appearance.
  • High: Enforces maximum black purity. No CMY corrections are applied, even for visual adjustment. Select this when absolute channel purity is required.
Black Start Defines the percentage at which Black starts being used in the separation. A higher value delays black generation, increasing the use of CMY in light and mid tones. Default: 15 %
Black Width Defines the amount of Black used in saturated colors. Higher values increase black in dark or fully saturated areas, while lower values rely more on CMY. Default: 80 %
Under Color Removal (UCR)

Defines how much CMY is replaced by black in different tonal ranges. Higher values increase black generation and reduce CMY in the corresponding areas.
 

  • Light: Controls under color removal in highlights. Higher values add more black in light tones. Default: 30 %
  • MidTone: Controls under color removal in midtones. Higher values add more black and reduce CMY in mid-range areas. Default: 80 %
  • Shadows: Controls under color removal in shadows. Higher values increase black in dark areas and reduce CMY. Default: 100 %

 

CMYK → ChannelChanger (GMG ColorPlugin)

The following settings are available for CMYK to ChannelChanger profiles used by GMG ColorPlugin for Photoshop. Instead of creating these profiles manually in GMG OpenColor, we recommend using the dynamic profiling in GMG ColorPlugin.

Parameter Description
Total Area Coverage (TAC) Defines the maximum total ink limit (sum of CMYK) as a percentage. Lower values can help prevent excessive ink coverage or drying problems during printing. Default: 330 %
Output Inks Select up to four output inks for the separation.
Key Color Only editable when using four output colors. Use this optionally to define the key channel when using four output colors.
The key color determines which of the selected output inks is treated as the main channel for dark tones and contrast, similar to the Black (K) channel in a CMYK setup.
GCR Level Adjust gray component replacement (GCR) to control the balance between CMY and black ink in extended color separations.
Higher values replace more CMY with black, improving stability and reducing ink usage. Lower values keep more CMY and additional inks active in dark or neutral areas, resulting in stronger color appearance.
Affects only CMYK inks.

 

RGB → ChannelExtender (GMG ColorPlugin)

The following settings are available for RGB to ChannelExtender profiles used by GMG ColorPlugin for Photoshop.

Parameter Description
Total Area Coverage (TAC) Defines the maximum total ink limit (sum of CMYK) as a percentage. Lower values can help prevent excessive ink coverage or drying problems during printing. Default: 330 %
Only one Profile (no Variants) Calculates a single profile with all output inks instead of multiple profile variants with all combinations of output inks.
Extension Inks Start at Defines the start percentage for additional inks used to extend the color space.

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