Important product change information
Since this article was originally published, Phantasm CS, Phantasm CS Studio and Phantasm CS Publisher have been separated into three individual plug-ins:
Existing customers of Phantasm CS / Studio / Publisher can find full details of how this affects their licenses by reading this article.
This tutorial provides a method to constrain Phantasm CS vector Halftone Filter or live Effects within the boundary of the original artwork as illustrated below:
- Adobe Illustrator CS2 or above
- Phantasm CS Designer, Studio or Publisher
- Phantasm CS Publisher only for optional final stage
Skill level: Intermediate
By default, the Phantasm CS plugin's Halftone Filter or live Effect tools produce results which are not absolutely constrained by the original object or artwork. Instead, the Halftone dot pattern extends where necessary to produce an accurate depiction of the print process upon which the effect is based. This is less of an issue the higher the effect's resolution, but there are circumstances when a Halftone pattern is best constrained to within the original artwork's boundaries.
If dealing with basic vector artwork or single vector objects such as the example at the top of this page, it can be done by the following simple process:
- Before applying the Halftone Filter or Effect, copy the artwork/object to the clipboard (Edit > Copy)
- Apply the Halftone Filter or Effect as normal
- Choose Edit > Paste in Front
- Select the Halftone original and the new copy which has been pasted directly in front, right-click in the artboard area and opt for Make Clipping Mask
This is the process that was used for this tutorial's first example above, and it works very well maintaining a vector result.
But what if the artwork to be Halftoned is more complex? For example, it could include multiple objects which rules out direct use of the Clipping Mask as the one below:
In this tutorial we are going to use an Opacity Mask method combined with other Phantasm CS tools to produce a perfect vector result.
Stage 1: producing Halftone artwork example
As there are many object types available within Illustrator, this example contains a number of important types to demonstrate the universal nature of this approach to constrain the Halftone dot pattern:
- Multiple complex paths
- Solid and gradient fills
- Process and spot colors
- Gaussian Blur Effect (optionally dealt with using Phantasm CS Publisher)
As a side-note, the example artwork of a spinning top in constructed using only the following inks:
- Pantone 408C spot ink
All occurrences of Black ink has been swapped to the spot color for printing purposes using Phantasm CS Publisher's advanced Swap Channels tool:
If you have problems viewing this movie, you can click on the movie file link: www.astutegraphics.com/movies/blog/constrained_halftone_seps.mov
Due to the number of complex shapes, we can't simply create a Clipping Mask. Also, as the object contains many shades of colors, we can't immediately make use of the Opacity Mask tool either to constrain the Halftone pattern.
Creating a Halftone
In this example, we are working in a CMYK document and will apply the Halftone as a non-destructive live Effect to allow for future adjustment:
- Select the artwork to which the Halftone is to be applied (if more than one object, first group everything together using Object > Group)
- Copy this group to the clipboard (Edit > Copy) for future use when creating an Opacity Mask
- Open Effect > Phantasm CS [version] > Halftone…
With the Effect window open, select CMYK as the Halftone Type:
As this artwork has all references of Black replaced with a spot color, we're going to use the Halftone tool's separation options to control the dot angle of the spot separation (which mimics the action a professional printer may take):
- Click on the Separations button
- In the Halftone Separations window, click on the spot color's default angle (0°) to make a change
- In the Edit Separation window, enter an angle of 45, followed by OK, and OK again in the Halftone Separations window
At this stage, you can make further adjustments to the overall Halftone settings such as resolution and then OK the Phantasm CS Halftone window.
Zooming into the resultant Halftone artwork, it may be seen how the Halftone dot pattern is overflowing the original artwork's boundary:
Creating an Opacity Mask
Choose Edit > Paste in Front to precisely overlay a copy of the original artwork. This will be the basis of the Opacity Mask which will be used to constrain the Halftone dots:
With the artwork copy still selected, choose select Edit > Edit Colors > Convert to Grayscale:
Why do this? Well, as we're going to use this copy of the artwork as the basis of a Opacity Mask, color is not an issue. But importantly, this basic color edit filter native to Illustrator converts all colors to grayscale including spot colors (Phantasm CS' own Desturate tool doesn't destroy spot color references). In many examples of artwork, this step is unnecessary, but it does cater for relatively obscure situations such as spot color drop shadows and blurs as is featured in this artwork.
Why further Phantasm CS operations are necessary
To explain why you can't use this artwork straight-away as the basis of a Opacity Mask in order to constrain the Halftone dots, let's see what happens if you did…
- Select the original artwork with the Halftone applied, plus the overlaid duplicate grayscale copy
- Via the Transparency panel (Window > Transparency if not already visible), select Make Opacity Mask from the panel's pull-down menu:
Note: This menu also allows the option to set all new Opacity Masks as inverted by default (New Opacity Masks Are Inverted), which has been enabled in this example. If this is not the case for you, you can invert the Opacity Mask once created by ticking the Invert Mask option in the Transparency panel.
Now if we look closely at the result, it may be seen that the artwork is variably transparent – directly in relation to the levels of gray in the overlaid artwork copy:
Creating a correct Opacity Mask
Undo the last operation (creating an Opacity Mask) so that only the grayscale artwork duplicate is selected once more. We are now going to use Phantasm CS' Duotone tool to ensure a correct Opacity Mask for this application.
- Open the Effect window via Effect > Phantasm CS [version] > Duotone…
- Within the Phantasm CS Duotone window, click on the Default Tone's color picker square
- In the Color Picker window, manually enter CMYK values of 0, 0, 0, 100% and OK this window
This has ensured a pure black Duotone will result. Next, click on the Duotone's shortcut button to create a 100% to 100% level "curve":
What this last step has done is to force all colors to pure black, ie. removing all shades of gray which was unwanted within the previously made Opacity Mask.
Click OK in the Phantasm CS Duotone window, select both the original Halftoned artwork and the Duotoned duplicate and opt for Make Opacity Mask from the Transparency panel's pull-down menu. The result should now be correct:
When zoomed into the artwork, it may be seen that the Halftone dot patterns are constrained within the original artwork's boundaries:
Optional step: dealing with drop shadows, glows, blurs and transparent images
One aspect of the previous result which can be improved upon is dealing with Illustrator's native drop shadow, glow and blur effects as well as any embedded transparent images. Zooming into an area of the artwork which uses as Gaussian Blur live Effect reveals that the Halftone dots in the blur region also start to fade out (in this example, ideally the Halftone dots should always be 100% tints of their respective inks):
Whereas this is detail that doesn't damage the overall image, it can be dealt with using the advanced Bitmap Alpha Channel control tool found in Phantasm CS Publisher.
The first step would be to release the Opacity Mask so that the overlying artwork duplicate can be worked on further. This is achieved by selecting Release Opacity Mask from the Transparency panel's pull-down menu:
- Ensure that only the top Duotoned duplicate artwork is selected and then open Phantasm CS Publisher's Curves window via Effect > Phantasm CS Publisher > Curves…
- Select Bitmap Alpha from the Channel menu
- Toggle to the graph's pencil mode (see highlighted button below)
- Draw a straight line along the bottom (0% Input) of the left half of the graph
- Draw a straight link along the top (100% Input) of the right half of the graph
Don't worry if you don't see any change on the artwork as this happens after the next stage. Simply OK the Curves window.
In the Appearance panel (Window > Appearance if not already open), drag the Phantasm CS Curves entry directly above the Phantasm CS Duotone entry as shown in the image below:
The Duotoned duplicate artwork should now appear as follows:
Note that the area in which the blur existed has now been converted to an abrupt change in tint from 0% Black to 100% Black. The profile of the blur differs compared to the original artwork, but this is now more accurately following the blur result on which the Halftone is based on in the original artwork beneath.
Finally, select the original Halftoned artwork and the overlaid Duotoned duplicate and make into an Opacity Mask via the Transparency panel once more:
Note: if you altered the Bitmap Alpha channel's stepped "curve" so that the lower line extended to nearly the right-hand edge of the graph, virtually all of the blur area will be rendered as a Halftone rather than being constrained to approximately the original artwork's boundary. As the Curve is applied as a live Effect, it's possible to experiment with this by clicking on the Phantasm CS Curve entry in the Appearance panel.