What is a halftone?
A printing press can only lay ink down or not — there's no '40% grey' ink. Yet magazines reproduce smooth photographs. The trick is the halftone: a grid of dots that vary in size. Big dots read as dark, tiny dots as light, and from a normal distance your eye blends them into continuous tone.
Dots that fool the eye
Look closely at a printed photo — a loupe helps — and you'll see it's made of dots, not smooth shading. In the shadows the dots are large and nearly touch; in the highlights they shrink to specks. The ink itself is always 100% solid; only the dot area changes. Your eye does the averaging.
This single idea, refined in the 1880s, is what made mass photographic printing possible, and it's still how every offset and most digital colour printing works today.
LPI: how fine the screen is
Halftone fineness is measured in lines per inch (LPI) — how many rows of dots fit in an inch. Higher LPI means smaller, denser dots and finer detail, but it demands smoother paper and a better press.
LPI vs DPI
They're related but different. LPI is the halftone screen ruling; DPI/PPI is your image resolution. A good rule is to supply image resolution about 1.5–2× the LPI — so 300 PPI images for a 150 lpi screen. More on this in our DPI guide.
| LPI | Typical use | Paper |
|---|---|---|
| 85 lpi | Newspapers | Newsprint |
| 133 lpi | General commercial | Uncoated / matte |
| 150 lpi | Magazines, brochures | Coated |
| 175–200 lpi | High-end, art books | Premium coated |
Screen angles and moiré
In full-colour printing, four halftone screens (C, M, Y, K) overprint. If they all used the same angle, the dots would collide into an ugly patterned clash called moiré. To avoid it, each ink is screened at a different angle — traditionally 15°, 75°, 0° and 45° for C, M, Y and K — so the dots interleave into tidy 'rosettes' instead.
Getting those angles right is a press concern, but it's why a colour photo is really four separate dot patterns layered with care.
Halftones as a design tool
Beyond reproducing photos, halftones are a look. Coarse, visible dots give that retro comic-book or risograph feel; a two-colour duotone maps shadows and highlights to two inks for a rich, stylised image. Screen printing and riso especially rely on halftone separations.
If you want to turn a photo into a halftone screen, a CMYK process screen, or a duotone — and export it as PNG or vector SVG — the Halftone & Duotone generator does it in the browser, with control over dot size and angle.
Frequently asked questions
Why do printers use halftones instead of just printing grey?
Most presses can only print solid ink or nothing — there's no variable-opacity ink. Halftone dots of varying size simulate continuous tones using only solid ink, which the eye blends at normal distance.
What is moiré and how do I avoid it?
Moiré is an unwanted interference pattern when dot grids clash. In CMYK printing it's avoided by screening each ink at a different angle. It can also appear when you scan an already-printed halftone — descreening or reshooting fixes that.
What LPI should I use?
Match it to paper and press: ~85 lpi for newsprint, 133–150 lpi for general commercial and magazine work on coated stock, and 175 lpi or higher for premium art printing. Your printer will specify.
What's the difference between a halftone and a duotone?
A halftone is a single-channel dot screen representing tones of one ink. A duotone uses two inks — typically mapping shadows to one and midtones/highlights to another — for a richer, stylised two-colour image.
Look closer next time
Put a loupe on any printed photo and the magic gives itself away — it's all dots. Once you've really seen it, screen angles and LPI stop being abstract. Reviewed June 14, 2026.