Flexo adjustment in Illustrator: handling spot colors

This article covers the specifics of handling spot color when simulating or compensating for flexo printing within Adobe Illustrator using Phantasm CS Studio or Publisher. It should be read in conjunction with the earlier articles in this mini-series.

General Curves and Levels control over spot inks

Spot colors are equally handled by Phantasm CS Studio and Publisher by the Curves and Levels tools. In each, it’s possible to control all spot inks used in the current selection via the Channel pull-down menu:

Notes:

• Changes to Curves or Levels in the default CMYK channel mode will make no effect on any spot colors within the selection. These have to be adjusted in their own Channel mode.
• It’s possible to adjust process CMYK and any spot channel in the selection simultaneously when the Curves and Levels tools are OK’d by individually adjusting the CMYK and then the spot channels curves/levels
• Photoshop’s Curves and Levels tools do not allow for control of CMYK and spot channels simultaneously. Therefore these tool’s settings files saved from Photoshop will only refer to CMYK channels. To maintain compatibility, Phantasm CS saves/loads Curves and Levels settings files individually for CMYK and each spot channel. If you wish repeat a combined CMYK and spot(s) adjustment, either re-open the Filter variant of the tool which recalls the last applied setting (in the same Illustrator session) or select Effect » Apply Curves/Levels. Alternatively, use the Actions or Graphic Styles systems.
• Spot control can be applied to flat-filled objects, multi-ink (“Device-N”) images, etc. The only special case is spot colored gradients, described next.

Spot colors within gradients

If a gradient is defined with spot color stops (you should never mix spot and process ink stops as a general best practice within Illustrator), the Accurate Gradient Adjustment option will be ineffective due to internal limitations. To overcome this, tick the Auto Rasterize option in the Phantasm CS color adjustment tools, ensuring that Preserve Spot Colors is ticked in Effect » Document Raster Effects Settings.

Another option is to use a small set of live Effects. This approach is non-destructive to the underlying gradient allowing for future changes which is harder to accomplish if an Accurate Gradient Adjustment is applied in a Curve adjustment resulting in many more gradient color stops.

1. Select one or more gradients filled with the same spot ink (they may each be different gradient profiles, but they can only contain tints of a single spot color).
2. Open the Effect variant of the Phantasm CS Swap Channels tool (Effect » Phantasm CS » Swap Channels).
3. Swap the spot ink entry to Process Black as shown below to change the gradient to a grayscale desaturated equivalent:

4. Apply the cut-off or compensation curve via the Effect variant of the Phantasm CS Curve tool’s CMYK channel as normal (the gradient is no longer a spot color).
5. Duplicate the Swap Channels entry in the Appearance panel (Window » Appearance, if not already open) by selecting the existing Swap Channels entry and clicking on the Duplicate Selected Item button on the bottom of the Appearance panel.
6. Drag this second Swap Channels entry below the Curves entry and then double-click on the lower Swap Channels entry to edit the live Effect.
7. In the Swap Channels window, select the original spot color as the target for the Process Black channel as shown below:

The results and the final live Effect stack in the Appearance panel can be seen below:

The upper gradient is the original constructed of a number of spot color stops of varying levels including below the 10% cut-off. The lower gradient is the result when the combination of Swap Channels and Curves live Effects are applied.

If you have Phantasm CS Studio or Publisher, you can examine the original file (ZIP compressed, for Illustrator CS3 and above) which may be downloaded by clicking here (173K).