What is a halftone in printing?

What it means for your file

Up close you see dots; at reading distance the eye blends them into continuous tone. The fineness of the screen is measured in lines per inch (lpi): about 85 lpi for newspapers, 133 to 150 lpi or more for magazines on coated paper, and much coarser for screen printing.

For offset printing, images are usually supplied at about 1.5 to 2 times the screen ruling, which is where the 300 ppi rule for a 150 lpi screen comes from. See DPI and PPI.

An example

A 50% gray is printed as dots that cover half the paper. In four-color printing, cyan, magenta, yellow and black each get their own screen at a different angle, and the dots together make every color. Screen printers usually print halftones much coarser, often around 45 to 65 lpi, because each dot has to pass through the mesh of the screen.

A common mistake

Sending a screen printer a full-color photo, or artwork with soft shadows, and expecting it to print as it looks on screen. Each ink is a separate screen that prints solid or not at all, so tones have to become a halftone at a frequency the shop’s mesh can hold. Ask what lpi they run before the separations are made.

Related terms

• Moiré pattern
• Dot gain