What dithering is, and why lasers need it
A photograph is made of smooth, continuous gradients - millions of subtly different gray values. A laser has no such vocabulary. At any given point the beam is either firing or it is not: a mark or bare material, black or white, on or off. There is no native "40% gray" in a burn. Dithering is the trick that bridges that gap.
Instead of a gray mark, dithering arranges thousands of tiny pure-black dots at varying densities. Pack them tight and your eye reads dark gray; space them out and it reads light gray; leave them out and it reads white. Step back from a newspaper photo and you see a face; lean in and you see only dots. That optical blending is what lets a one-bit device reproduce continuous tone.
The reason lasers need this rather than just varying power is reliability. A dithered image asks the machine to do one thing - fire at full power or skip - which every laser does consistently. Ask a beam to hold a precise 63% power for a precise mid-gray and you depend on a linear power-to-darkness relationship that most machines and materials do not have.
Grayscale vs dithering
Every photo engraving uses one of two strategies to represent tone. Understanding the trade-off is what lets you pick correctly instead of copying a setting off a forum.
Grayscale (power-scaled)
Here the image stays gray and the laser modulates its power pixel by pixel to make lighter and darker marks. In theory it is the richer method: continuous power should give continuous tone. In practice it depends on a genuinely linear power-to-darkness curve, which most diode lasers lack. The symptoms are banding (tone jumping in visible steps) and a washed-out, low-contrast look. Grayscale rewards a calibrated CO2 and forgiving materials - anodized aluminum, some coated metals, cast acrylic.
Dithering (halftone dots)
Here tone is broken into pure black-or-white dots before the file ever reaches the laser. Because every dot is full-power-on or nothing, dithering ignores the power-linearity problem completely. It is more tolerant of cheap diode optics, uneven materials and beginner calibration, which is exactly why it is the default for photo work across the hobby. The cost is a visible grain up close and a dependence on getting DPI right - both of which the rest of this guide handles.
| Grayscale / power-scaled | Dithering | |
|---|---|---|
| How tone is made | Variable laser power per pixel | Density of pure black dots |
| Depends on | Linear power-to-darkness curve | Clean, consistent single dot |
| Typical failure | Banding, washed-out | Muddy if dots merge |
| Best on | Tuned CO2, anodized metal, acrylic | Diode lasers, wood, slate, leather |
| Beginner verdict | Use only if calibrated | Safe default |
Every dithering algorithm compared
"Dithering" is not one thing - it is a family of algorithms that decide where the dots land, in two camps. Ordered dithers (Threshold, Bayer, Newsprint) use a fixed pattern - fast and predictable. Error-diffusion dithers (Floyd-Steinberg, Jarvis, Stucki, Atkinson) push each pixel's rounding error into its neighbours for a more organic, photographic grain. Here is how the ones you will meet behave.
| Algorithm | Type | Character & grain | Best use |
|---|---|---|---|
| Threshold | None (1-bit cut) | Pure black/white, no dots - hard edges only | Logos, line art, text, stencils - never photos |
| Ordered / Bayer | Ordered | Regular cross-hatch pattern, visible grid | Fast previews, stylised retro look, very fast lasers |
| Floyd-Steinberg | Error diffusion | Fine, tight, even grain | The default for photos - smooth materials, higher-res lasers |
| Jarvis-Judice-Ninke | Error diffusion | Wider, more open, softer dots | Slate, coated metal, diode lasers whose dots merge |
| Stucki | Error diffusion | Sharp, clean, high contrast - like Jarvis but crisper | Detailed portraits where you want punch without mud |
| Atkinson | Error diffusion | High contrast, blown highlights, light overall | Light-marking materials, high-key portraits, that "Mac" look |
| Newsprint / halftone | Ordered (dot grid) | Classic round halftone dots, print-shop look | Large signage, coarse materials, deliberately vintage pieces |
The two that matter most: Floyd-Steinberg and Jarvis
Ninety percent of the time you are choosing between these two. Both diffuse error to neighbouring pixels; the difference is how far. Floyd-Steinberg spreads each pixel's error across 4 nearby pixels, giving a tight, dense grain. Jarvis-Judice-Ninke spreads it across 12 pixels over a wider radius, giving larger, more separated dots. The practical upshot:
- Floyd-Steinberg keeps the most fine detail and looks best when your laser can resolve small dots cleanly. It is fast and it is the right first thing to try.
- Jarvis (and its cousin Stucki) opens the dots up so they do not touch and flood. If Floyd-Steinberg comes out as a dark smear, Jarvis usually rescues it.
- Stucki is Jarvis with a crisper, higher-contrast weighting - a good pick when you want open dots but still sharp edges.
- Atkinson deliberately throws away some error, so it lightens the image and blows out highlights. That is a feature on light-marking materials and high-key portraits, a bug on a dark wood plaque.
How DPI and line interval interact with dithering
This is where most muddy engravings are born. DPI (dots per inch) - and its metric twin, line interval in millimetres - sets how tightly the rows of dots are packed. It is the single most misunderstood number in laser photo work, because higher is not better. Dithering already decided where the dots go; DPI decides how physically close together the laser tries to put them.
Set the DPI higher than your laser's dot can resolve and adjacent dots overlap. The white gaps carrying your highlights fill in with burn, the whole image slides toward black, and the fine grain turns into a solid dark blob. This is dot merge - the number-one cause of "why does my portrait look like a shadow?"
| Laser | Sensible DPI | Line interval |
|---|---|---|
| 5-10 W diode | 254-318 DPI | 0.08-0.10 mm |
| 20 W diode | 318 DPI | 0.08 mm |
| 40-60 W CO2 | 333-500 DPI | 0.05-0.076 mm |
The rule that ties DPI to dithering: the line interval should roughly match the diameter of the smallest clean dot your machine makes. A diode with a 0.08 mm focused dot has no business running at 500 DPI (0.05 mm interval) - you are commanding dots closer than the beam can separate, so they merge no matter which algorithm you chose. Match the interval to the dot, then match your image's pixel resolution to that interval.
Wider algorithms buy you headroom here. Because Jarvis and Stucki space their dots further apart, they tolerate a slightly higher DPI before merging than Floyd-Steinberg does. But the cleaner fix is almost always to lower the DPI first. Our Laser Calculator converts between DPI, interval, physical size and engraving time so you can size the image correctly before you dither.
Choosing a dither per material
The same dithered file behaves completely differently depending on what it is burning into, because two things change with the surface: how much the dot blooms, and which direction the material marks. Here is where each algorithm tends to land - all figures are starting points to confirm with a test grid.
| Material | Marks | Suggested dither | Why |
|---|---|---|---|
| Wood (birch, maple) | Dark | Floyd-Steinberg | Fine grain reads well; grain of the wood hides dot texture |
| Slate | Light | Jarvis / Stucki | Flaky surface blooms; open dots stop merge, invert the image |
| Coated / anodized metal | Light | Jarvis or grayscale | Coating tolerates power scaling; wider dots if dithering |
| Acrylic (cast, painted back) | Frosts / light | Atkinson or grayscale | High-key look suits translucency; often better power-scaled |
| Leather | Dark | Floyd-Steinberg | Fine grain on a forgiving, self-hiding surface |
Dark-marking vs light-marking
One rule flips your whole workflow. On dark-marking surfaces (wood, leather, cardboard) the laser darkens what it touches, so the photo stays positive - you burn the shadows. On light-marking surfaces (slate, glass, anodized aluminum, coated metal) the laser removes a dark layer to reveal a pale mark, so you must invert the image first and burn the highlights. Dither the same way in both cases; you just invert before or after.
Every material also has its own starting power, speed and dot behaviour. The per-surface walk-throughs go deep on each:
- Engraving photos on wood
- Engraving photos on slate
- Engraving photos on metal
- Engraving photos on acrylic
- Engraving photos on leather
Contrast and gamma prep before dithering
Dithering is only as good as the tones you feed it. An error-diffusion algorithm can only place dots where the image tells it to - it cannot invent contrast that is not there. Prep the grayscale before you dither, never after (post-dither editing just smears the dots).
- Contrast stretches the gap between light and dark. A boost of roughly 1.2x-1.5x is typical. Push until shadows read genuinely dark and highlights genuinely bright, but stop before the darkest zones collapse into detail-free black - dithering cannot recover tone from a flat black patch.
- Gamma / brightness shifts where the midtones sit. On dark-marking wood or leather, nudge it down a touch so midtones do not fill in. On light-marking slate or anodized metal, raise it so faces stay bright after you invert. Gamma is your main lever for keeping skin tones open.
- Highlights matter most. The eye forgives crushed shadows far more than it forgives muddy highlights. Keep the brightest parts of a face genuinely white so the dots thin out there and give the portrait its life.
Aim for an image that looks slightly too contrasty on screen. Dithering spreads that punch back into believable tone, so a flat input yields a flat, lifeless burn. The Photo to Laser tool bundles grayscale, contrast, gamma and dithering into one pass.
Diagnosing muddy vs washed-out results
Almost every failed photo engraving is one of two opposite problems. Learn to tell them apart and you can fix any burn in one adjustment.
Muddy / too dark
The image reads as a dark smear with lost detail in the shadows and midtones. The dots have merged into solid black. In order of what to try:
- Lower the DPI / widen the line interval - the top fix by far. Your dots are closer than the laser can separate.
- Switch to a wider algorithm - Floyd-Steinberg to Jarvis or Stucki, so the dots start further apart.
- Raise gamma / lower contrast slightly so fewer pixels are pure black going in.
- Only then reduce power or increase speed - power is the last lever, not the first.
Washed-out / too faint
The image is pale and lifeless with no real blacks - it looks like a weak photocopy. The marks are too light or too sparse:
- Boost contrast before dithering so real shadows exist to place dots into.
- Increase power or slow down so each dot actually marks the surface.
- Check for accidental double-dithering - if you dithered in EngraveBot and LightBurn re-dithers, the pattern collides and thins out. Set LightBurn to
Pass-Through. - On light-marking materials, confirm you inverted - a faint negative means the highlights and shadows are swapped.
Machine-specific notes
The right dither depends as much on your laser as your material, because the machine sets how big and clean a single dot is. These are honest starting points - your exact numbers come from a test grid, and no setting is guaranteed safe until you have burned one.
5-10 W diode
The workhorse of the hobby, and the machine most helped by dithering. Its focused dot is relatively large and tends to bloom, so it merges easily. Favour Jarvis or Stucki over Floyd-Steinberg if you see mud, keep DPI in the 254-318 range, and lean on dithering rather than grayscale - power scaling on a bare diode is rarely linear enough for clean gray. Wood, leather and slate are its natural photo materials.
20 W diode
Higher power but a similar dot geometry to the smaller diodes, so the same cautions apply - just faster. Floyd-Steinberg becomes viable on smoother materials because you can afford to move quickly and keep marks crisp, but drop to Jarvis on slate and coated metal. Stay near 318 DPI; the extra wattage tempts people into higher DPI, which merges dots just as readily as on a 10 W.
40-60 W CO2
The finest dot and most linear power curve of the three, which unlocks Floyd-Steinberg at higher DPI (333-500) for photographic grain and credible grayscale once calibrated. CO2 excels on wood, slate, leather, acrylic and glass. Even here, dithering is the safest default for a first burn - move to grayscale only after proving power linearity on a test grid.
Compare every dither on your photo - free, in your browser
Frequently asked questions
What is the best dithering for laser engraving photos?
Floyd-Steinberg is the best all-round default - fine grain, good tonal range, fast. On materials where dots merge (slate, coated metal) or on lower-resolution diode lasers, switch to Jarvis or Stucki for wider, more separated dots. Always confirm on a test grid on your actual material.
What is the difference between Floyd-Steinberg and Jarvis dithering?
Both diffuse error to neighbouring pixels, but Floyd-Steinberg spreads it to 4 pixels while Jarvis-Judice-Ninke spreads it to 12 over a wider radius. Floyd-Steinberg gives tighter, finer grain for smooth materials and high-resolution lasers; Jarvis makes wider, more open dots that survive when your beam blooms or merges.
Should I use grayscale or dithering?
Dither, unless your machine holds a proven linear power curve. Dithering's pure on/off dots sidestep the power-linearity problem that makes grayscale band and wash out on most diode lasers. Reserve grayscale for a tuned CO2 or forgiving materials like anodized metal and acrylic.
Why does my dithered engraving look muddy?
The dots are merging - your DPI is too high for the dot your laser can make, or the input was too dark. Lower the DPI or widen the line interval first, switch to a wider algorithm like Jarvis, and boost contrast before dithering so the highlights stay open.
Keep going
Put this into a full workflow with how to convert a photo into a laser-ready file, spell out every LightBurn control in LightBurn image settings explained, then pick your surface: wood, slate, metal, acrylic or leather.