Before choosing a dithering algorithm, choose a mode. There are three ways to put an image on material: as dots of full marks (dither), as varying power (grayscale), or as paths (vector). Most disappointing engravings use the right algorithm in the wrong mode.
Dither when the material makes one tone
On most wood, slate, painted surfaces and coated metal, a laser either marks a spot or it does not. Dithering simulates shades with the density of those marks, which is why it is the default for photographs. Image Lab photo prep has 15 algorithms in four families: error diffusion, halftone screens, Bayer ordered grids and plain threshold. The dithering guide compares the ones to learn first.
Grayscale when the material follows the power
Grayscale image modes, such as LightBurn's Grayscale, change power with the tone of each pixel instead of placing dots. That only works where the material darkens gradually as power rises, which a test grid on that material will show you. For carving actual depth, as in a relief, the tone is a height: make a 16-bit depth map in Depth Studio, because an 8-bit map can leave visible steps on a deep, smooth carve.
Vector when the image is really shapes
Logos, lettering, line art and anything that will be cut or scored belong in paths, not pixels. Paths stay sharp at any size and can be given a cut, score or engrave operation. Vectorize in Image Lab, or turn a photo into line art and a traced SVG in Vector Artist, then check the paths at the finished size.
Do not convert twice
A dithered image is already final dots. If the laser software dithers it again, the pattern turns to mush. Image Lab writes its LightBurn project with the image in Threshold mode for exactly this reason; if you import the PNG yourself, set the image mode to Threshold. Then match the line interval to the DPI: 25.4 divided by the DPI gives the interval in millimetres, so 254 DPI is 0.1 mm.
A quick decision list
- Photo on pale wood: dither, as prepared, around 254 DPI.
- Photo on slate or black-painted stone: dither, inverted, because the laser marks those lighter than the surface.
- Logo, text or line art: vector, or threshold if it must stay a raster.
- Relief or carved depth: a 16-bit depth map, not a dither.
- Anything you are unsure about: a small crop of each mode on scrap, side by side.
Frequently asked questions: Photo Prep
Is grayscale better than dithering?
Neither is better everywhere. Grayscale varies power with tone, so it only works where the material darkens in step with power. Dithering works on any surface that takes a mark, because it only needs mark or no mark. Run a small test grid on the material to see whether its response is gradual or abrupt.
Can I dither a logo?
You can, but the edges turn into dots and small text breaks up. A logo is shapes, so vectorize it, or use plain threshold, which keeps edges crisp. Keep dithering for photographs and soft shading.
What DPI should I prepare a photo at?
It depends on the material and your spot size. The free photo dithering presets use 254 DPI for wood and painted stone and 300 DPI for slate and tile. More DPI than the spot can resolve merges dots into dark patches, so match the line interval to the DPI and test.