Dithering turns a greyscale image into the on/off dots a laser can actually produce. Understanding it is most of photo engraving.
The modes and when to use them
- Jarvis — general purpose. Good default for landscapes, objects, most artwork.
- Stucki — softer transitions, holds shadow detail better. Best for faces.
- Floyd–Steinberg — sharper, can look noisy on smooth gradients.
- Ordered / Bayer — visible regular pattern. Choose it when you want a halftone look, not for realism.
- Threshold / 1-bit — no dithering at all. Line art and logos only.
The part that matters more than the mode
Your material has a usable tonal range and it is narrower than your image. Wood gives you roughly four or five distinguishable tones; anodised aluminium about three; slate a generous six.
So before you export:
- Convert to greyscale.
- Compress the tonal range to what the material can reproduce — lift the blacks, pull the highlights down. It will look flat on screen and correct on the material.
- Add a little local contrast (large radius, low amount unsharp mask).
- Then let the machine dither.
Test at final size
A face that looks superb at 80mm turns to mush at 30mm, because the dither dots stop resolving. Always test at the size you'll actually engrave.
LaserPecker publish their own documentation on this topic — worth reading alongside these community notes.
Official article