A duotone is a grayscale image reproduced with two inks instead of a standard CMYK build. The darker ink usually carries shadow structure while a second ink shapes highlights and midtones. The result can add depth, a strong colour character and a highly controlled look to a two-colour print job.
Photoshop uses “Duotone” as an umbrella term for one, two, three or four inks: monotone, duotone, tritone and quadtone. They are production techniques, not merely a two-colour screen effect.
Choose the number of inks deliberately
| Treatment | Inks | Typical use |
|---|---|---|
| Monotone | One | A black, sepia or single spot-colour image. |
| Duotone | Two | A dark structural ink plus a highlight or accent ink. |
| Tritone | Three | More controlled midtones and colour depth. |
| Quadtone | Four | Complex tonal work using multiple spot inks. |
The inks, paper and print sequence change the result. A named spot colour is not enough to guarantee appearance: request a drawdown or proof for colour-critical work.
Create a duotone in Photoshop
- Save an editable RGB or CMYK master before conversion.
- Convert a copy to 8-bit grayscale with Image → Mode → Grayscale.
- Choose Image → Mode → Duotone.
- Select Monotone, Duotone, Tritone or Quadtone, then choose the intended inks from the appropriate colour library.
- Edit each ink’s curve to control how it appears in shadows, midtones and highlights; keep the darkest ink first.
- Preview, proof and check overprint behaviour before final output.
Plan the handoff
Do not casually convert a duotone to CMYK: that changes its spot-ink intent into process approximations. Confirm whether the printer expects a PDF with named spot separations, a supplied image in a particular format or a finished composite file. Inspect the final separations in output preview, and make sure each ink name matches the printer’s specification.