How to Prep a Halftone for Risograph Printing
Risograph prints one spot color at a time. To print a photograph, you have to split it into color layers and halftone each one. Here's the complete workflow from photo to print-ready files.
Why halftone for Risograph?
A Risograph drum holds one ink color. Each pass through the machine lays down one layer of dots — either ink or no-ink, no in-between. To get the illusion of midtones, you halftone each layer first. The varying dot sizes let your eye blend the ink and the paper into a smooth tone.
Layer two or three halftones at different angles, and you get rich, slightly-imperfect images that have become the signature riso aesthetic.
The full workflow
Pick your inks
Most prints use 2 or 3 spot colors. Common Risograph combos:
Classic combos: Pink + Blue (vaporwave portrait), Pink + Yellow (sunset / warm), Black + Fluorescent (graphic poster). Our Riso tool lets you preview any combo before you print.
Split into channels
You need one grayscale image per ink — each grayscale tells the Risograph "lay down more ink where this is dark."
- For 2-color prints: split your photo into a "warm" channel (red/pink/yellow tones) and a "cool" channel (blue/green/cyan tones).
- For 3-color prints: simulate CMY by splitting into cyan, magenta, yellow channels.
- Use Photoshop's Image > Adjustments > Channel Mixer, or our Riso tool which does this automatically.
Halftone each layer separately
Each grayscale becomes a halftone with its own settings:
| Setting | Recommended |
|---|---|
| LPI | 43–55 LPI (riso drums hold finer detail than screens) |
| Dot shape | Round (safest), or Square for graphic look |
| Dot angle, Color 1 | 15° |
| Dot angle, Color 2 | 75° |
| Dot angle, Color 3 | 45° |
Different angles per layer prevent moiré when the inks overlap. This is the same principle as CMYK offset printing.
Export SVG per layer (Pro)
Risographs print from PDF or vector — sharper than raster. Pro SVG export gives you one vector file per ink layer, every dot a real shape that scales to any size without losing edge crispness.
Preview the overlap
Before sending to print, simulate the final result. Our Riso tool shows you exactly how your layers will overlap, with authentic ink colors and slight registration offset — so you can see if your Pink + Blue portrait looks the way you imagined.
Adjust contrast, balance the layers, then export the final files for print.
Sending to a Risograph studio
Most riso studios want one PDF per layer, named clearly:
poster_01_pink.pdfposter_02_blue.pdf
Put each layer at 100% black (the Risograph translates "black on this layer" into "ink for this color"). Keep all files the same size and trim — registration depends on it.
Troubleshooting
The two ink layers don't line up
Riso registration is always slightly off — that's the look. If it's too much, ask your studio about manual registration adjustment, or design with the offset in mind.
My midtones look muddy
Either your halftone LPI is too high (lower to 43), or the two ink colors are competing. Try one warm + one cool color rather than two analogous shades.
Highlights are pure paper
Lower the threshold so smaller dots survive into the lightest regions, giving texture.
Ready to prep your riso print?
Free at 600px. Pro (€9 one-time) unlocks full resolution and SVG vector export — essential for Risograph prep.