What is a halftone?
A printing press can’t print grey. Each plate either puts ink on the paper or leaves it bare. Halftoning fakes every tone in between with a grid of dots: large dots that almost touch read as dark, small dots surrounded by paper read as light. At normal viewing distance the eye blends them back into a continuous image.
Newspapers, magazines, screen-printed posters and risograph zines all rely on it. A digital halftone like this one measures the brightness of the photo under every cell of the grid and draws a dot whose area matches that tone.
LPI, cell size and screen angle
LPI (lines per inch) counts the rows of dots in an inch. Typical values are around 85–100 LPI for newsprint, 133–150 LPI for magazines on coated paper and 175 LPI or more for art books. The finer the screen, the less visible the dots.
This tool sets the screen by cell size, in pixels of your image. To convert: LPI = image resolution in PPI ÷ cell size. A 12 px cell printed at 300 PPI gives 25 LPI, a bold pattern you notice on purpose. A fine 150 LPI screen would need 2 px cells at 300 PPI, which is why a visible halftone is a design choice rather than a way to reproduce a photo faithfully.
Screen angle rotates the grid. 45° is the classic angle for a single ink because diagonal rows are the least noticeable: the eye picks up horizontal and vertical lines much more easily. When inks overlap, each gets its own angle, traditionally 30° apart (for example 15°, 45° and 75°, with yellow at 0°), so the grids form small rosettes instead of a coarse moiré.
Why misregistration happens
Every ink is printed from its own plate, stencil or drum, in its own pass. Paper stretches with humidity, feeds a fraction of a millimetre differently each time, and every machine has mechanical tolerances. Offset printers fight this with registration marks and press checks; on a risograph or a screen-printing table the shift becomes part of the look.
A slight offset between two inks creates the overlapping fringes people associate with riso prints. The misregistration sliders reproduce exactly that: they move the whole second plate relative to the first, dots and image together.
Tips for print and for screen
For print
- Export at the final print size. A finished halftone does not survive resampling: scaling it later blurs or breaks the dots.
- Ask your print shop about the smallest dot they can hold. Tiny highlight dots disappear and nearly solid shadows fill in first, so keep the cell size comfortably above that.
- Ink spreads on uncoated paper (dot gain), so prints come out darker than the screen. Lift Brightness a little for newsprint or uncoated stock.
- Use SVG when the halftone will be resized, recoloured, cut or engraved. In Illustrator, Inkscape or Figma each ink is its own group of shapes.
- For two-colour work, put the darker ink on the 45° screen and keep the second ink about 30° away.
For screen
- Use bigger cells than you think. Dots need to be several pixels wide to survive compression and resizing on social platforms.
- Judge the pattern in the 100% view. A scaled-down preview of fine dots can show moiré that is not in the file.
- Turn on Transparent paper to export only the ink, so the halftone can sit on any background in a layout.