Gradient Map

A gradient map replaces colour, it doesn’t tint it

A tint blends something over what is already there, so the original hues survive underneath and fight whatever you added. A gradient map throws them away entirely. Each pixel’s luminance is read as a position from zero to one along a ramp, and the colour sitting at that position on the ramp becomes the pixel. Nothing of the original hue remains.

That is why a gradient map is so much more decisive than an overlay, and why it unifies a mismatched set of images so effectively: every one of them comes out of the same ramp, so they cannot disagree about colour. It is also why it is unforgiving — if the luminance is wrong, the colour will be wrong, and no amount of adjusting the ramp will fix it. Get the tones right first.

Duotone is the same operation with the ramp reduced to a shadow and a highlight colour, optionally with a midtone. If you find yourself using two stops, Duotone is the more direct control.

Why the interpolation setting is not a detail

Between any two stops the ramp has to invent the colours in the middle, and how it does that decides whether the result is any good. Interpolating in RGB walks a straight line through a cube that is not perceptually uniform, and straight lines through that cube go through grey. The classic demonstration is blue to yellow: the mathematical midpoint of those two in RGB is a dead neutral, so the middle of the ramp — where most of your midtones land — is mud.

OKLCH is a perceptual space with lightness, chroma and hue on separate axes. Interpolating there keeps chroma up across the middle instead of collapsing it, and takes the hue around the shorter arc of the wheel rather than cutting across the centre. The same two stops produce a ramp whose middle is as saturated as its ends.

The practical rule: pick RGB when you want the desaturated middle, which is occasionally exactly the effect. Pick OKLCH for everything else, and particularly for any ramp whose stops are far apart in hue.

Where it goes in the stack

After the tonal work and before the texture. Everything that shapes luminance — exposure, levels, curves, and any effect that flattens or crushes tone — should happen first, because luminance is the gradient map’s only input. Everything that adds physical texture, grain especially, should happen after, so it isn’t remapped along with the picture.

When you’d reach for it

When you want a set of images to feel like one body of work, or when you want a colour scheme that has nothing to do with what was in front of the camera. It is the fastest route from a photograph to a graphic, and unlike most colour work it survives being pushed hard.

Every option, from the app

Generated from the registry the app publishes, so this list is whatever the current build actually ships — not a copy of it.

Interpolation

RGBOKLCH

Related effects

• RisographSpot-ink riso printing: luminance separated into two or three inks, each screened at its own angle with mottled grain and multiplied over tinted paper — mis-registration and all.
• DitherOrdered dithering: Bayer and blue-noise threshold masks quantised to real machine palettes — Game Boy, PICO-8, CGA, EGA, NES, C64, ZX Spectrum and more.
• Film GrainFilm grain that responds to tone the way emulsion does — peaking in the midtones, on named stocks from Tri-X and HP5 to Portra, Velvia and Cinestill 500T, plus digital sensor noise.

It’s one of the free effects — open the app and it’s there, no signup. Open V3KTR · all the FX · how it works