Why a photo is not laser-ready
A camera photo is millions of smoothly graded colours. A laser is a single dot that is either on or off, moving in straight lines. Between those two worlds sits the job of this guide: flattening colour into tone, tone into dots, and dots into a file your machine understands. Skip that translation and you get the classic beginner result - a dark, muddy smear that looks nothing like the picture on your screen.
The good news is that the process is the same on every laser and every material. Only the numbers change. Once you understand the five decisions below, you can reproduce a clean engraving on wood, slate, metal, acrylic or leather without guessing.
Step 1 · Pick the right photo
Ninety percent of a good engraving is decided before you touch any settings. The laser can only reproduce contrast that already exists in the image, so start with a photo that has:
- A clear subject - one face, one pet, one object. Busy group shots lose all detail at engraving sizes.
- Strong, directional light. Flat, even lighting gives you flat, lifeless tone. Side light that carves out cheekbones and fur is what the laser turns into depth.
- A plain or removable background. A cluttered background competes with the subject for the laser's limited tonal range. Cut it out first with the Background Remover.
- Enough resolution. Aim for at least the pixel count of your final engraving in dots - a 100 mm engraving at 300 DPI needs roughly 1200 px on that side.
Step 2 · Grayscale and contrast
The laser ignores colour entirely - it only sees brightness. Converting to grayscale lets you see exactly what the machine will see, which is why every serious workflow does it first. But a straight grayscale conversion almost always looks weak, because camera photos pack most of their information into the midtones.
Two adjustments fix this:
- Contrast stretches the difference between light and dark. A boost of roughly 1.2×–1.5× is typical; push until the shadows read as genuinely dark and the highlights as genuinely bright, but stop before the darkest areas turn into flat black blobs with no detail.
- Gamma / brightness shifts where the midtones sit. On dark-marking materials like wood you often lower it slightly; on light-marking materials like slate or anodized aluminum you raise it so faces stay bright.
You are aiming for a picture that looks a little too contrasty on screen. The dithering step below spreads tone back out, so a punchy input gives a lifelike output.
Step 3 · Dither vs grayscale
This is the decision beginners get wrong most often. There are two ways to represent tone with a laser:
Grayscale (power-scaled)
The laser varies its power to make lighter or darker marks. It sounds ideal, but it depends on your machine holding a perfectly linear relationship between power and mark darkness - which most diode lasers do not. The result is often banding and a washed-out look. Grayscale shines on well-tuned CO2 machines and on materials with a wide tonal range.
Dithering (halftone dots)
Instead of gray, the image is broken into thousands of pure black-or-white dots. Stand back and your eye blends them into continuous tone - exactly like a newspaper photo. Because every dot is full-power on or nothing, dithering sidesteps the power-linearity problem entirely. That reliability is why it is the default for photo engraving.
The two dithering algorithms you will actually use:
| Algorithm | Character | Best for |
|---|---|---|
| Floyd–Steinberg | Fine, tight grain | Smooth materials, higher-resolution lasers, small detailed pieces |
| Jarvis | Wider, more open dots | Slate, coated metals, diode lasers whose dots tend to merge |
If your first test looks like a dark smudge, your dots are merging - switch from Floyd–Steinberg to Jarvis or lower the DPI. The Dithering Lab lets you flip between them and preview the burn on simulated material before committing. For the full breakdown, see best dithering settings for laser engraving.
Step 4 · DPI and interval
DPI (dots per inch) - or its metric twin, line interval in millimetres - controls how tightly the dots are packed. It is the single most misunderstood number in laser engraving, because higher is not better. If you pack dots closer than your laser can physically resolve, they overlap, flood the material and destroy the very detail you were trying to keep.
| Laser | Sensible DPI | 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 |
Match the DPI to the smallest clean dot your machine makes, then match the image's pixel resolution to that. Our Laser Calculator converts between DPI, interval, physical size and engraving time so you are not doing the arithmetic by hand.
Step 5 · Match the material
The same prepared image burns completely differently on different surfaces, and one rule flips everything: which direction the material marks.
- Dark-marking (wood, leather, cardboard): the laser darkens what it touches. The photo stays positive - burn the shadows.
- Light-marking (slate, glass, anodized aluminum): the laser removes a dark surface layer to reveal a pale mark. You must invert the image - burn the highlights.
Beyond direction, each material has its own starting power, speed and dithering preference. We keep per-material walk-throughs here:
- Engraving photos on wood
- Engraving photos on metal
- Engraving photos on acrylic
- Engraving photos on leather
- Engraving photos on slate
Step 6 · Export to LightBurn
Once the image is grayscaled, contrasted and dithered, export it as a PNG - it is lossless, so no compression artefacts sneak in. In LightBurn:
- Drag the PNG onto the workspace and place it on an Image layer.
- Set the image mode. If you dithered in EngraveBot, choose
Pass-Throughso LightBurn burns your dots exactly as drawn, without re-dithering them. - Enter the power, speed and DPI/interval from your material guide.
- Set line interval to match the DPI you chose in Step 4.
If your machine does not run LightBurn, the same PNG imports into most engraving software the same way. EngraveBot can also export a ready-to-run .lbrn2 project with the settings already filled in - see LightBurn image settings explained for every option spelled out.
Step 7 · Burn a test grid
No guide can give you the exact number for your machine, your material batch and your lens. What takes the guesswork out is a test grid: a small array of squares, each burned at a different power/speed combination. You burn it once, pick the square that looks best, and use those numbers for the real piece.
It costs two minutes and one offcut, and it is the difference between hobbyists who "get lucky sometimes" and people who hit it first try every time. Generate one with the free Test Grid Generator and burn it on the back of your material.
Prep your photo now - free, in your browser
Seven common mistakes (and the fix)
- Leaving the photo in colour. Always grayscale first so you see what the laser sees.
- DPI too high. Muddy result - lower it before changing power.
- No contrast boost. Flat input, flat engraving. Push contrast until it looks slightly too strong.
- Forgetting to invert on slate/glass/anodized. You get a photographic negative.
- Busy background. Remove it so the subject keeps the tonal range.
- Re-dithering in LightBurn. If you dithered already, use Pass-Through, not Dither, or you dither twice.
- Skipping the test grid. The one shortcut that always costs more time than it saves.
Frequently asked questions
What file format does a laser need for a photo?
A raster image - PNG is best because it is lossless. Import it onto an image layer in LightBurn or your machine's software. SVG is only for cut or score outlines, not for photo tone.
Should I dither or use grayscale?
Dither, unless you know your machine holds linear power scaling. Dithering's on/off dots are far more forgiving on diode lasers and textured materials.
What DPI should I use?
254–318 DPI for a typical 10 W diode; up to ~500 DPI for a tuned CO2. Higher is not better - match it to the dot your laser can actually make.
Does my photo get uploaded anywhere?
Not with EngraveBot. Grayscale, contrast, dithering and export all run locally in your browser, so the image never leaves your computer.
Keep going
Pick your material next: wood, metal, acrylic, leather or slate - or go deeper on dithering and 3D relief engraving.