Full Color Stencil Art with Halftoning

Step 2 Choose and Separate an Image

Select a subject. I went with Andre the Giant because he's fairly well known from Shepard Fairey's stencil work.

Resize your image:

• Open the image in Photoshop.
• Image > Image Size
• I set "document size" to 800% width/height, at 300 ppi, giving me about 7x9 inches

Then we need to convert it to CMYK, normalize it and brighten it a bit so that when we halftone the circles don't intersect:

• Image > Mode > CMYK
• If it asks about Flattening, click "Flatten"
• Normalize using Image > Adjustments > Auto Level, or do it by hand (recommended)
• Open Image > Adjustments > Levels and in the minimum output level box enter 128 (this will, effectively, make the image brighter)

Separate the four color channels:

• Select the "Channels" window (next to "Layers", or select from the "Window" toolbar)
• Make only the "Cyan" channel visible
• Select all
• On the "Layers" window, create a new Layer and paste the channel
• You should now see just the Cyan channel in black and white, save this as a jpg
• Do likewise with the three other channels (Magenta, Yellow, and Black)

When you're done, you should have four separate black and white images, one for each channel.

There is probably a faster way to do the separation, or to do it in Illustrator directly. If you know, share the technique in the comments!