Glossary · Technology

Laser

Dithering

A process in which a laser reproduces greyscale from dots. Because it usually only knows "burn" or "don't burn", the grey tone is created by the density of the dots.

Explained in more detail

Many lasers can only render two states cleanly per dot. Dithering converts a greyscale image into a pattern of black and white dots whose density simulates brightness. Common algorithms are Floyd-Steinberg (1976), Jarvis and Stucki, which spread the error of each rounding to neighbouring dots, as well as ordered patterns and halftones. LightBurn offers the modes Threshold, Ordered, Atkinson, Dither, Stucki, Jarvis, Newsprint, Halftone and Grayscale, among others. The quality depends strongly on a suitable line interval: it should be roughly the same as the spot size of the laser.

Where does the term come from?

The English verb to dither means to tremble or hesitate. The term comes from signal processing, where noise is added deliberately to spread out rounding errors. Floyd-Steinberg is named after Robert W. Floyd and Louis Steinberg.

In practice

• For photos on wood, Jarvis and Stucki often give calmer results, while Floyd-Steinberg looks more detailed but grainier.
• Before engraving, increase the contrast and sharpness of the image; flat photos become even flatter on wood.
• On slate and anodised aluminium, the engraving is light, so you usually have to invert the image there.
• If the result is too dark, increase the line interval or reduce the power instead of just changing the brightness of the image.

Not to be confused

Not to be confused with grayscale mode, in which the laser varies its power per dot. That only works on materials that discolour to different degrees depending on energy.

Frequently asked questions

Which dithering mode is best for photos?

There is no best one for all materials. For wood, Jarvis or Stucki is a good start; with new materials, test two or three modes on small sample areas.

Why does my lasered photo look too dark?

Usually the lines are too close together or the power is too high, so the dots run into each other. Increase the line interval and lighten the bright areas of the image beforehand.