Fine-tune separations

By default, GMG OpenColor uses its best-match algorithm to calculate color separations with the smallest possible Delta E for each output channel, ensuring the closest match to the target values.

However, you can manually adjust color values in the plugin’s conversion dialog to fine-tune separations, for example, to reduce production costs or to adapt the color separation to specific requirements.

When you modify color values in the separation rules matrix, GMG OpenColor automatically recalculates all other values in the background and updates the separation matrix in real-time. The live Delta E preview provides instant feedback on how your changes will impact the printing result, allowing you to anticipate potential limitations, communicate them to your customer in advance, and align expectations accordingly.

The following example shows how to strike the right balance between cost efficiency, printability, and color accuracy.

Example: optimize light-colored artwork for a printer without LLK

Let’s say you want to print artwork with a light color, Pantone 2260 C for this demo, on a digital printer that does not support light black ink (LLK).

In this case, the presence of black in the separation would be colormetrically accurate, resulting in a Delta E of 0.01:

However, especially with coarse screening, this black ratio could appear as large, visible dark dots in the print. To prevent this, click into the 'Black' Column of the Pantone 2260 C source ink row and set the value to zero (0.0). This removes black from the Pantone 2260 C separation.

Customized values are automatically marked with a blue dot, making them easy to distinguish from automatically calculated values at any time. Additionally, the source ink's name is indented and accompanied by an icon for easier identification.

As soon as you set Black to zero, all non-user-defined values are recalculated immediately, and as you can see, the values for 'Cyan' and 'Yellow' have been slightly adjusted to ensure the best possible result for your customization:

With a Delta E deviation of 0.26, the expected result remains excellent and stays below the threshold of visibility.

Now you might wonder if reducing even more dark color by replacing Cyan with Green would further improve print quality, so let’s find out. Set Cyan to 0 and raise the Green ratio instead.

As you can see, this results in a Delta E of 2.86, shifting the color further from the reference. In most cases, this trade-off is not worth it. For our demo use case, removing only Black provides the best balance between printability and color accuracy.

Reset custom changes to default

If you accidentally changed values or aren't satisfied with your adjustments, just click on the Reset Changes button above the separation matrix to restore the default settings.

Now that you know how to fine-tune values and use the live Delta E preview to evaluate color shifts in real-time, you can confidently customize separations to specific requirements before starting the conversion.