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What it does
Most risograph filters tint an image and add noise. This one separates it the way a duplicator actually would, then screens each ink at its own angle, which is where the characteristic moire and colour breakup come from.
How it works
The image is separated into four channels using an under-colour split, so a black component is pulled out rather than being built from all three inks at once.
Each channel is assigned a spot ink: a teal, a red-orange, a yellow, and a near-black green. These are mixed subtractively, so overlapping inks darken as real ink does.
Every layer is screened on its own rotated grid, at roughly eighteen, minus fourteen, zero, and forty-two degrees. Separate angles are what stop the four screens from collapsing into one pattern.
Dot size is driven by area, not by radius, so ink coverage stays perceptually correct as tone changes.
The stock is a warm off-white, and a per-cell value wobble stands in for uneven drum inking.
What each control changes
Detail
Sets the screen ruling. Lower detail gives a coarser, more obviously mechanical dot; higher detail tightens it toward offset.
Contrast
Applied before separation, so it changes how much black is pulled out versus built from coloured inks.
Intensity
How completely the separation replaces the original. Lowering it reintroduces the original colour beneath the four inks, which softens the effect without coarsening the screen.
Scale
Adjusts the cell geometry the screens are laid on.
Reseed
Changes the inking wobble, which shifts the character of the imperfection without changing the separation.
Good for
Gig posters and print-feel promotional artwork
Zines and small-run editorial
Giving flat digital illustration a printed provenance
Less suited to: Work that must reproduce a brand colour exactly; the separation deliberately reinterprets colour through four fixed inks.