What it does
Collapses smooth gradients into a few flat tonal bands for a screen-printed, cel-shaded look. Band per channel or by brightness, with a gamma bias to push the steps toward shadows or highlights.
Posterization started as an economy. Printing a poster meant cutting a separate stencil or plate for every tone, so designers reduced photographs to three or four flat areas of ink and let the shapes do the work. The look outlived the constraint: flat bands with hard edges read as deliberate and graphic in a way smooth gradients never do, which is why the technique moved from the print shop into pop art and film posters.
Digitally there are two honest ways to do it, and they look different. Banding each color channel independently is the classic version: where the red, green, and blue steps disagree, the hue lurches at every band boundary, producing the saturated, slightly-off colors of a cheap print. Banding brightness alone keeps the original hue and saturation riding along, so the image breaks into clean tonal steps of its own colors, which is the cel-shading read.
The craft is in where the bands fall. Evenly spaced steps crowd everything interesting into the midtones, so a good posterize lets you push the band distribution toward the shadows or the highlights, deciding which end of the tonal range keeps its detail. The bands can also be blended partially back against the source, banding the image without fully flattening it. On video the band edges crawl along gradients as the light moves, a live contour line that still frames cannot show.
Signature looks
Two-ink poster
A handful of brightness bands, flat and graphic. The screen-printed poster look, shapes first, shading abolished.
Cheap print
Each channel banded on its own, so the hue jumps at every step edge. The saturated wrong-but-right colors of low-budget printing.
Cel shade
Footage with its lighting collapsed into clean tonal steps, like an animator painted the frame in three tones of each color.
Try it on your own footage
This effect runs live in the Modulate editor, free with no signup — or start from the free tool page for a guided setup.
Common questions
What does posterizing an image do?
It quantizes the image’s tonal range into a small number of flat levels, so smooth gradients become abrupt steps. Fine shading disappears, shapes and edges take over, and the image reads as printed or painted rather than photographed.
Why is it called posterize?
The name comes from poster printing, where every tone required its own plate or stencil and another pass of ink. Reducing a photograph to a few flat tones made mass printing practical, and the flat-banded look became the visual language of posters themselves.
What is the difference between posterize and threshold?
Threshold is posterize taken to its extreme: a single cutoff that reduces the image to exactly two levels. Posterize keeps several bands and can preserve the image’s own colors within them, so it simplifies the image where threshold silhouettes it.
How do I posterize a photo without wrecking its colors?
Band the brightness instead of the color channels. Quantizing luminance alone lets the original hue and saturation survive inside each band, giving clean tonal steps of the photo’s own palette. Per-channel banding is the choice when you want the hue to lurch on purpose.
Can you posterize a video?
Yes, and it is one of the effect’s best modes: as light moves through the footage, the band edges crawl along gradients like animated contour lines. In Modulate the Posterize effect runs live on images and video in the editor and stacks with halftone, grain, and gradient map.
Related effects
Threshold effect
Reduces the image to two colors with a hard cutoff between light and dark, with optional outlined edges.
Gradient map
Recolors the image by mapping its dark and light areas onto a gradient you design.
Risograph effect
Recreates risograph printing: a few bold ink colors layered on paper, each slightly out of register.
Tone pixelate effect
Splits the image into shadows, midtones, and highlights, and redraws each band as flat pixel blocks on its own offset grid with custom fill and outline colors, like a layered screen-print poster.