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Using vector imagery (Illustrator), I'd like to convert an object's outer-glow or drop-shadow into halftone dots using Effects > Pixelate > Color Halftone. However, running this on a path, shape, text, or compound path with a drop shadow will (correctly) apply that effect to the main shape, not the effect.

Can I separate out the shadow/glow as a new layer that I can apply the effect on? Or is there another workaround?

I'd like the halftone dots to take the general shape of the text otherwise I'd just create a block and place it behind.

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    There's really no effective way to do what you are thinking out of the box. I completely understand the thought process. But it just doesn't work as one would expect. You're better off creating your own shadows, glows, etc. Halftones are customarily created in prepress. But if you want your own dots perhaps using the default halftone patterns provided with Illustrator would be among the better options, then custom brushes work well. Typically, if you want to create dots... none of the "filters" or "effects" work well, except AstuteGraphics' Phantasm plug in.
    – Scott
    Jan 12, 2021 at 19:38
  • Also running the color halftone effect creates 4 color dots.. if the art is then commercially printed, there's a high risk for a moiré.
    – Scott
    Jan 12, 2021 at 19:41
  • @Scott Great points - I'm actually looking to do a grayscale (black dot only) effect, but this is interesting to learn about how it all works.
    – armadadrive
    Jan 13, 2021 at 4:15

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Halftone effect actually converts the shape to raster image. Also blur, glow and shadow effects are raster images.

Those raster images are generated for what's shown on the screen, Illustrator still keeps the original shape (can be as well vector as raster image) hanging around. You see the effect as an insert in the Appearance panel. There you can reopen the effect dialog for readjustments or remove the effect.

Let's assume you have applied Outer Glow to a vector shape. Apply Object > Expand Appearance and Ungroup to make the generated raster image free. Then apply to it Color Halftone.

You can again expand the appearance to get the halftoned glow as a free image. Now you have got exactly what you wrote you want. But I suspect you will not be happy. It's a raster image.

You can in theory trace it back to vector but that's not practical. The image is blurry and contains transparent overlapping colors. You will not get clean dots. And the high number (thousands) of the traced new paths can slow down your system. Save at least your work before trying tracing because your system can freeze under too high load.

If you want your glow as a controllable number of vector dots something else is needed - an effect plugin or a better workflow than using Illustrators effects in a standard way with default settings.

If you can accept single color dots (much simpler that what Illustrator's color halftone generates) you can get something usable even in Illustrator. An example:

enter image description here

In the left there's a random vector shape. It has got Outer Glow effect. The third image is the glow raster image separated. It's got by applying Expand Appearance and Ungroup. The original shape is moved away. The rightmost image is the original shape and a half-toned vector version of the glow simply moved to the same place.

The home-made vector glow isn't perfect. You can see that it's too dense in dark areas which make waist of the shape thicker. With high zoom you could also see that the dots have irregular shapes.

But the vector glow is easy to make in Illustrator. At first draw a rectangle, place it below the separated raster glow and fill the rectangle with Illustrator's basic dot pattern:

enter image description here

Scale the pattern dots small enough with Object > Transform > Scale > Patterns.

Apply Gaussian Blur to the pattern (not to the glow). The radius should be set so that the dots become lighter in their midpoints, but the gaps between the dots are still visible. Zoom in to be sure. You must also have white background to see it reliably.

enter image description here

Select both the glow shape and the blurred pattern. Rasterize them as one item with white background and high enough resolution. 300 dpi is OK for the screen.

Apply Object > Live Trace to get it as B&W vector. It's a good idea to place the original vector shape on the top to see how tracing settings affect to the glow effect:

enter image description here

The outlines and high zoom in show how well or badly it succeeded:

enter image description here

The round dots are not optimal. Somehow better result is possible if one copies the glow shape to Photoshop, converts it to grayscale and bitmap color mode. Photoshop has several bitmap halftoning options which do not make the dark are too dense, the waist of the shape stays as narrow as it originally was. This is Diffusion dither half-toning:

enter image description here

Converted from bitmap mode to RGB, pasted back to illustrator, traced and layered with the original shape the result is this:

enter image description here

As seen from far away it looks like the blur based glow and it is vector, but unfortunately it has much more paths and nodes than the dot pattern based version.

Photoshop's Halftone Screen half-toning in the bitmap color mode gives also good results which as vectorized are a little lighter. But the dots are like crosses. 0,5 pixel blur in tracing reduces the number of paths substantially by removing the smallest dots:

enter image description here

I stop here. There's many possibilities still available. If it happens that you are in a hurry and not interested in tinkering, do as user Scott suggested; get a plugin for vectorized half toning patterns.

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  • Amazing answer. Thank you @user287001!
    – armadadrive
    Jan 13, 2021 at 15:14
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First, rathe than trying to harvest the (raster) gradients in the (raster) effects. it's best to create your own gradients. This is often not that difficult. Remove the Effect which was originally in place. Create new shapes or copy existing shapes, offset, and apply a standard gradient fill.

The easiest, most effective method to create halftones in Illustrator - assuming you want clean vector dots - is to use the Phantasm Plug In from AstuteGraphics.com. I realize this is not a "free" option. They do provide a free trial though. So, for a single project, it may be worth exploring. I, personally, find Astute items well worth their pricing. If you do this a great deal.. really.. it's worth the cost.

The Phantasm plug in offers a wealth of control...

enter image description here

Simply create a gradient and call the plugin, that's all that's necessary.

enter image description here

As you can see the Color Halftone Effect results in an odd sized raster image. There's no clipping mask there. For some reason the embedded raster image has this large white margin which is actually part of the raster image. Whereas the expanded Phantasm art is just a collection of standard vector circles.

Barring the plug in....

It's possible to use the default patterns shipped with Illustrator. Specifically the Basic_Graphic_Dots patterns. While not really halftones, you can achieve some halftone-like fills with these.

enter image description here

A third option may be Blends. Simply create a blend between two circles. You can then turn that into a brush or merely copy the blend and position to create a pseudo-halftone.

enter image description here

Disclosure: I have received free software from Astute Graphics in exchange for my evaluation and opinion. However, I do not benefit in any way if someone chooses to purchase anything from Astute Graphics.

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  • Looks like a useful plugin for some applications. Thanks @Scott!
    – armadadrive
    Jan 13, 2021 at 15:15

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