Halftone for screen printing: the complete beginner's guide
Every T-shirt with photographic detail, every zine cover with a portrait, every magazine with continuous-tone imagery; they're all halftoned before printing. This guide covers what halftone is, how to pick LPI and angle for your specific substrate, and the common mistakes that make a design look muddy instead of crisp.
Why halftone matters
Screen printing applies ink in binary: a pixel is either printed or not. There's no physical way to print 50% gray. To simulate grays, the artwork is pre-processed with a halftone filter: dark regions become clusters of large dots that touch and form solid areas, light regions become small sparse dots that the eye reads as light gray. From a normal viewing distance, the dots blur into smooth gradations. Up close, you see the mechanism.
Every piece of screen-printed merchandise, newspaper photo, and magazine is halftoned. Modern inkjet and digital textile printers also halftone internally. Understanding it is a baseline skill for anyone taking design to physical print.
Six-step workflow
Understand what halftone actually is
Halftone is a dot-pattern reproduction technique that simulates continuous tone (grays or mid-tones) using dots of varying size. Where the source image is dark, the dots are large and touch; where it's light, the dots are small or absent. Your eye can't resolve individual dots at normal viewing distance, so it blends them into apparent gradients. It's the foundation of every screen-printed T-shirt, newspaper photo, and magazine print.
- Screen print can't physically produce gray; halftone is how it fakes it
- Your eye stops seeing dots around 45+ LPI at arm's length
- Halftone is invisible to the viewer, obvious to the printer
Pick the right LPI for your substrate
LPI (Lines Per Inch) is the halftone grid density. The right LPI depends on what you're printing on. Fabric absorbs and spreads ink, so finer grids merge into mud. Smooth substrates hold finer detail. Always ask your print shop for their recommended LPI before finalizing.
- Cotton T-shirt: 45-55 LPI
- Premium garment / paper: 65-85 LPI
- Poster / smooth paper: 85-100 LPI
- Magazine quality: 133-150 LPI
Set the right grid angle
Rotating the halftone grid prevents visible regularity. For a single-color print, 45° is the industry default because the human eye is less sensitive to diagonal patterns than horizontal or vertical. For CMYK process printing, each channel uses a different angle to prevent moiré (interference patterns between channels).
- Single-color: 45° always
- CMYK: C 15°, M 75°, Y 0°, K 45°
- Never stack two channels at the same angle
Choose the dot shape
Dot shape changes the aesthetic but not the density. Circle is the standard: smoothest gradations, works on every substrate. Square has a slight 80s zine / graphic-design feel. Line gives a risograph or newspaper-editorial look. Elliptical (rare in free tools) splits the difference on very-light-to-mid-tone transitions.
- Circle = default for production
- Square = retro / editorial style
- Line = zine / risograph aesthetic
- Don't mix shapes within one design
Watch out for ink coverage limits
Screen printing on dark garments uses underbase + color layers. Total ink coverage in the darkest halftone spots can exceed the garment's ability to hold ink, causing bleed. Cap your darkest black halftone at 85-90% coverage for safety, not 100%.
- Total ink coverage should stay under 260% for dark cotton
- Cap darkest black dot at 85% to avoid ink flooding
- Discuss with your print shop, because different shops have different caps
Export and verify before sending to print
Export a lossless PNG at your source resolution. At 100% zoom, verify that your lightest areas have visible-but-tiny dots (not vanished) and darkest areas are fully filled (not blocked up). Send a test file to your printer first; they'll often adjust LPI and angle further for their specific press.
- PNG, not JPG: compression kills halftone dots
- Check at 100% zoom, not fit-to-screen
- Printer may re-halftone on their side, so share the source too
Common mistakes
Related resources
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