A Risograph is a stencil duplicator: each colour is burned onto its own master and printed as a separate pass. Because the paper moves between passes, the plates never line up perfectly, and the inks are semi-transparent soy-based spot colours rather than process CMYK. Those two facts — misregistration and ink translucency — are what the eye actually reads as "riso", far more than the palette does.
This filter reproduces the process rather than imitating the result. The image is converted from RGB to CMYK coverage, and each of the four plates is screened at its own angle — roughly +15.5 degrees, -15.5 degrees, 0 for yellow and 44.7 degrees — so the overlaps form a rosette instead of a moire. Each plate is then offset by a small, plate-dependent amount, exactly like paper drift between passes. Where two plates overlap, the inks multiply rather than replace, which is why riso greens and purples appear that no single ink contains.
| Plate | Ink | Screen angle |
|---|---|---|
| C | Teal | about +15.5 degrees |
| M | Orange-red | about -15.5 degrees |
| Y | Yellow | 0 degrees |
| K | Deep green-black | about 44.7 degrees |
The paper is never pure white. It sits at a warm off-white, and a low-amplitude grain runs across the whole frame, because uncoated stock never takes ink evenly. Lower the detail slider for a coarser screen and a more obviously printed result; raise it to keep photographic detail. Everything renders locally with Canvas 2D and exports a full-resolution PNG.