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Photo Engraving on Laser: Resolution, Dithering, and Materials

A photo engrave that looks sharp and tonal on screen and muddy or overburnt in real life is almost always a resolution, dithering, or image preparation problem: not a power setting problem. This guide covers every variable in the chain: DPI, scan gap, gamma, dithering mode, and material-specific adjustments that produce consistent, photographic-quality results.

DPI and scan gap: the fundamental relationship

A laser engraver doesn't actually "know" about DPI. It sweeps back and forth in horizontal lines, and the distance between those lines is the scan gap (also called line interval in LightBurn). The scan gap determines the effective DPI of the engrave.

Scan gap (mm) = 25.4 ÷ DPIDPI = 25.4 ÷ scan gap (mm)

25.4 is the number of millimetres in an inch: the bridge between metric scan gap and imperial DPI. These two formulas are all you need.

Example: You want to engrave at 254 DPI.
Scan gap = 25.4 ÷ 254 = 0.100 mm.
In LightBurn: Edit → Cut Settings → Line Interval = 0.100 mm.

DPI quick reference
DPIScan gapUse when
1270.200 mmFast draft / material test
2540.100 mmStandard: logos, text, simple art
5080.050 mmPhotos and portraits
6000.042 mmFine portrait detail
10000.025 mmSlate, anodized, glass

Higher DPI doesn't always mean better results

Higher DPI = tighter scan gap = more scan lines per mm = more heat deposited per area. On wood, going from 254 to 508 DPI without reducing power will over-darken the image and lose shadow detail. When you increase DPI, reduce speed or power proportionally to keep total energy density constant. Run a test grid at your new DPI before the full job.

Image preparation workflow

The source image quality determines the ceiling of your result. No setting in LightBurn recovers detail that wasn't in the original file.

1
Start with the highest-resolution original you have
At least 1:1 pixel-to-dot at your target DPI. For a 100×100 mm engrave at 508 DPI, the source image should be at minimum 2000×2000 px. Upscaling a 300 px photo to 2000 px doesn't add detail.
2
Convert to 8-bit grayscale
Colour information confuses the laser's tonal mapping. Convert to grayscale first, then adjust. In Photo Prep: upload → the tool converts automatically. In Photoshop: Image → Mode → Grayscale.
3
Adjust gamma (1.2–1.8 for most wood)
Laser engraving compresses midtones: shadows go too dark and highlights wash out. Gamma correction lifts the midtones before they're compressed by the dithering process. A gamma of 1.4–1.6 is a safe starting point for basswood. Reduce to 1.0–1.2 for veg-tan leather.
4
Apply CLAHE contrast enhancement for portraits
CLAHE (Contrast Limited Adaptive Histogram Equalisation) boosts local contrast without blowing out highlights or crushing shadows. Especially effective on portraits with uneven lighting or low-contrast backgrounds.
5
Choose and apply dithering
Dithering converts the continuous-tone grayscale image into the binary (on/off) pattern the laser can reproduce. See the dithering guide below. Apply dithering in Photo Prep, then export as PNG: never JPEG (compression artefacts engrave as noise rings).
6
Export as PNG, import to laser software
In LightBurn: File → Import → select PNG. Set the layer to Image, DPI to match your scan gap. If you pre-dithered in Photo Prep, set LightBurn's dither mode to Threshold (pass-through). In xTool CS: import as bitmap, select Engrave mode.
Open Photo Prep →DPI / Scan Gap Calculator

Dithering modes: choosing the right one

Dithering is the process of converting a grayscale image into a binary dot pattern that fools the eye into perceiving tones. The laser is binary: it either fires or it doesn't, so every shade of gray must be approximated with a pattern of dots. Different algorithms suit different subjects.

Floyd-Steinberg
Error diffusion: random-looking
Portraits, pets, people
Distributes quantisation error to neighbouring pixels. Produces organic, photographic-looking texture with no visible pattern.
Ordered / Bayer
Regular grid pattern
Products, flat art, logos
Fixed matrix creates a predictable halftone. Cleaner on artwork with defined edges. Can produce moiré if scan gap doesn't match pattern size.
Jarvis / Stucki
Error diffusion: wider kernel
High-res engraves, slate, tile
Spreads error over a larger neighbourhood for smoother tonal gradients. Slower but produces excellent results at 500+ DPI.
Atkinson
Error diffusion: high contrast
Text and line art alongside photos
Propagates only 75% of the error, pushing tones toward black or white. Punchy, high-contrast look. Loses subtle shadows.
Threshold (none)
Binary: no halftone
High-contrast logos on dark wood
Every pixel becomes pure black or pure white. No tonal information: good for logos, bad for portraits.

If you pre-dither in Photo Prep and import the result into LightBurn, set LightBurn's mode to Threshold so it passes the image through without applying a second dithering pass on top.

Material-specific settings and advice

The same image requires different preparation depending on the material. The table below covers typical starting points: always run a test grid on your specific material batch before the full job.

Basswood / birch plywood

DPI: 254–508Gap: 0.05–0.10 mmGamma: 1.2–1.6Dither: Floyd-Steinberg
Image contrast advice

Boost midtones; basswood engraves pale: push contrast higher than you think

Heat and safety notes

Thin plywood can warp at tight scan gaps. Use honeycomb or pin bed. Dry the wood first.

Maple / cherry / walnut

DPI: 254–400Gap: 0.063–0.10 mmGamma: 1.0–1.3Dither: Floyd-Steinberg or Jarvis
Image contrast advice

Dense grain absorbs more energy: reduce speed or add passes rather than increasing power

Heat and safety notes

Hardwoods accumulate heat faster than plywood. Slow, lower-power passes outperform fast-high-power on portraits.

MDF

DPI: 254–508Gap: 0.05–0.10 mmGamma: 1.4–1.8Dither: Ordered (Bayer) or Floyd-Steinberg
Image contrast advice

MDF engraves very dark: lift shadows aggressively in image prep or highlights will blow out

Heat and safety notes

MDF produces fine dust and fumes. Strong ventilation essential. Never use moisture-resistant MDF: glues release toxic fumes.

Leather (veg-tan)

DPI: 254–508Gap: 0.05–0.10 mmGamma: 1.0–1.2Dither: Floyd-Steinberg
Image contrast advice

Natural contrast: minimal image adjustments needed. Avoid over-darkening.

Heat and safety notes

Chrome-tanned leather releases hexavalent chromium: never engrave. Veg-tan only. Lower power, higher speed for cleaner results.

Slate / dark stone

DPI: 500–1000Gap: 0.025–0.05 mmGamma: 1.6–2.2Dither: Jarvis or Stucki
Image contrast advice

Slate engraves white: invert the image. Boost highlights heavily to get tonal range.

Heat and safety notes

Stone absorbs and holds heat: slow speeds help. Very high DPI (600+) produces photographic results on dark slate.

Acrylic (cast, coloured)

DPI: 254–400Gap: 0.063–0.10 mmGamma: 1.0–1.4Dither: Threshold or Floyd-Steinberg
Image contrast advice

Engraves frosted white on coloured acrylic: works like a reverse image. Light areas in photo = unengraved = coloured acrylic.

Heat and safety notes

DO NOT engrave clear acrylic: smoke redeposits and makes it foggy. Coloured/opaque acrylic only for photo work. Requires CO2 or dedicated diode IR wavelength.

Anodized aluminium

DPI: 254–600Gap: 0.042–0.10 mmGamma: 1.0–1.3Dither: Ordered (Bayer)
Image contrast advice

Engraves to bare metal (silver). High contrast photos work best. Subtle tones are difficult.

Heat and safety notes

Fiber laser only for permanent results. Diode/CO2 can engrave anodizing with coatings but marks are less durable.

Common problems and fixes

Image too dark overall
Reduce power 10–15%, or increase speed. Check gamma setting: higher gamma (1.4–1.8) lifts midtones before they crush.
Highlights washing out / flat result
Boost contrast in image prep. Apply CLAHE. On wood, try a lower gamma (closer to 1.0) to preserve the bright areas.
Dotted or stripy pattern visible
Increase DPI (reduce scan gap). At 127 DPI, individual scan lines become visible on smooth materials: move to 254 or 508.
Background engraving when it should be white
The image has near-white but not pure-white pixels. In Photo Prep, lift the gamma or apply a levels adjustment to push near-whites to pure white.
No tonal range, looks like a stencil
Wrong dither mode: Threshold gives binary results. Switch to Floyd-Steinberg or Jarvis for tonal gradation.
Fuzzy or soft edges
Source image resolution too low for the engrave size and DPI. Check that source pixel count ≥ (mm width × DPI / 25.4) at minimum 1:1.
Prep a Photo →DPI / Scan Gap CalculatorSpeed × Power Test GridLaser Settings DB

What Makers Say

★★★★★5.0· 6 reviews
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★★★★★

"Used it with a Glowforge: engraved beautifully with no changes. I will be purchasing more digital downloads from this shop."

: Anna

★★★★★

"I was struggling with lining up my NFC business cards. I was able to not only line them up much better but also do multiple cards at once: making that job so much easier."

: Camp

★★★★★

"Excellent quality and design. Cut clean and neat!"

: LYNN

★★★★★

"Great jigs. Appreciate the time saved not having to build this from scratch!"

: Bruce

★★★★★

"Excellent quality. Item as described. Expectations exceeded."

: Michael

★★★★★

"This template made my slate coasters so much easier. 4×4 coasters from Michaels drop in easily and are easy to remove. Def worth it."

: chris

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