Laser engraving photos: material, image preparation and dithering

Software & files7 min readUpdated: 10/2026

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A photo on wood or slate is one of the most popular laser projects and one of the most temperamental. At any given spot the laser can only burn or not burn. To still get shades of grey, the software has to convert the image. This guide shows what matters: material, image preparation, line interval, image mode and a test grid.

Which material works

A photo needs an even surface with good contrast. Anything that brings its own texture or colour differences competes with the image.

Material	Suitability	What to watch out for
Maple, lime (linden), alder	very good	light and calmly grained, engraving turns dark
Birch plywood with a good face veneer	good	check for glue pockets and grain
Pine, spruce	poor	hard growth rings make the image streaky
Slate	very good	engraving turns light, invert the image
Anodised aluminium, dark	very good	engraving turns light, fine line interval possible
Leather, vegetable-tanned, light	good	engraving turns dark, only use safe leather
Coated tiles	possible	separate technique, only with a test tile
Glass	rather not	only frosts, fine grey tones are lost

With wood, the grain decides. Dense latewood rings burn differently from the soft wood between them, and you see that in faces immediately. More on this in Laser cutting and engraving wood. For leather: chrome-tanned leather and many synthetic leathers do not belong in the laser, see Laser engraving leather.

Tiles are usually coated for photos. With the so-called Norton White Tile method, you spray a paint containing titanium dioxide onto a white tile, the laser melts it dark into the glaze wherever it hits, and you wash off the rest. The OMTech description refers to CO₂ lasers with a fine focus. Only a test will show whether it works with your machine.

Glass is the most difficult choice for photos. A CO₂ laser frosts the surface, and a diode laser needs a coating on clear glass. Fine gradations in skin tones are rarely preserved. Details are in Laser engraving glass, stone and slate.

Preparing the image

A photo that looks good on screen almost always turns out too dark on wood. Wood has its own base tone, and burned dots run into each other slightly. So edit the image beforehand, in an image editor or directly in the laser software.

Crop: Crop tightly around the subject. A face should fill a large part of the area; small faces in a group lose every detail at 10 cm width.
Check the resolution: xTool recommends at least 1,000 × 1,000 pixels. A blurry phone photo does not get better through the laser.
Background: Remove busy backgrounds or lighten them heavily. This draws the eye to the subject and saves laser time.
Greyscale: Convert the image to greyscale, the laser cannot do colour.
Brightness and contrast: Lighten the midtones noticeably and raise the contrast. The darkest shadows should not be pure black, otherwise all detail disappears there.
Sharpen: Sharpen slightly, for example with Unsharp Mask. This keeps edges such as eyes and hair visible after engraving.

LightBurn has the “Adjust Image” tool for this, with brightness, contrast and gamma, and xTool Studio offers similar sliders for the image. General information on file formats is in Preparing laser files.

Line interval, DPI and dot size

The laser scans the image line by line. The line interval sets how far apart the lines are. According to the LightBurn documentation, DPI = 25.4 divided by the line interval in mm.

Line interval	DPI	Lines per cm (xTool)
0.2 mm	127	50
0.1 mm	254	100
0.08 mm	318	125
0.05 mm	508	200

The right value depends on the size of your laser dot. According to LightBurn, the ideal is an interval at which the lines just touch, with no gaps and no overlap. If they overlap, the image becomes too dark. If gaps remain, it looks pale and streaky.

An example: Ortur gives a dot of 0.08 × 0.08 mm for the Laser Master 3 20W, and Sculpfun gives 0.08 × 0.10 mm for the S30 Ultra 33W. By calculation you end up with a line interval of 0.08 to 0.1 mm, so around 250 to 320 DPI. These are the manufacturer’s nominal values. How wide the burned dot really turns out on your material depends on focus, power and material. LightBurn therefore recommends the Interval Test in the range of 120 to 300 DPI.

For fine work, LightBurn also has Dot Width Correction. It shortens the burn runs because the beam makes dots longer than they should be. According to the documentation, the ideal is about half the beam width, at most the line interval.

Image modes: greyscale or dithering

Schematic of the same gradient, on wood from light to dark. On the left the laser changes the power per dot, on the right it burns every dot fully or not at all and creates the grey tone through dot density.

There are two ways to create grey tones.

Greyscale (Grayscale): The laser changes the power per pixel between minimum and maximum power. This only works if the material responds evenly to small differences in power. According to LightBurn, a diode laser can produce very good gradations this way, but it is harder to set up than dithering. With CO₂ lasers, greyscale tends to produce engraving of varying depth, so 3D effects, instead of shading. xTool, on the other hand, names greyscale as the default in xTool Studio and expressly recommends the mode for blue light, meaning diode lasers. Both are true for the respective system: try it on your machine.

Dithering: Each dot is either burned or not. The grey tone comes from the density, as in newspaper printing. There are two families.

Error diffusion (Floyd-Steinberg, Jarvis, Stucki, Sierra, Atkinson): The software distributes the rounding error of each pixel to the neighbouring pixels. Floyd-Steinberg uses few neighbours and produces fine, wavy patterns. According to xTool, Jarvis distributes to 12 neighbouring pixels and looks softer. Stucki is similar, slightly sharper and, according to LightBurn, quicker to calculate.
Ordered (Ordered, Halftone, Newsprint): A fixed grid determines where dots sit. The pattern is even but visible.

Mode	LightBurn	xTool Studio	When
Jarvis	Jarvis	Jarvis	first choice for photos with soft gradients, usually the best according to LightBurn
Stucki	Stucki	Stucki	photos, slightly sharper, weaknesses in the midtones
Floyd-Steinberg or simple error diffusion	Dither (method not named in detail)	Floyd	detailed images, LightBurn calls Dither very good for photos
Atkinson	Atkinson	Atkinson	subjects with flat areas, loses very light and very dark regions
Ordered	Ordered	Bayer	graphics with large areas, even grid
Halftone, Newsprint	yes	no	decorative halftone look, needs high DPI
Greyscale	Grayscale	Grayscale	evenly responding materials, test on diode
Threshold	Threshold	no	black and white only, for logos, not for photos

Rule of thumb for a start: Jarvis for wood and leather, and on slate and anodised aluminium also Jarvis or Stucki. If the image looks too blotchy, test Atkinson or greyscale.

Starting values as a baseline

The following ranges are rules of thumb for your first test grid, not manufacturer’s figures. They apply to dithering on light wood such as lime or maple. Your manufacturer’s material profiles take priority.

Machine	Power	Speed	Line interval
10 W diode	40 to 70 %	100 to 200 mm/s	0.08 to 0.1 mm
20 W diode	30 to 60 %	150 to 300 mm/s	0.08 to 0.1 mm
40 W diode	25 to 50 %	200 to 400 mm/s	0.08 to 0.1 mm
40 to 55 W CO₂	15 to 30 %	200 to 400 mm/s	0.1 mm

For comparison, a published example from xTool’s photo course: lime wood with power 55, speed 160, 100 lines per cm and Jarvis. xTool does not name a machine for it. For slate you will find starting values in Laser engraving glass, stone and slate, and for anodised aluminium in Laser engraving metal.

Here is how to proceed:

Set the focus cleanly, see Laser focus.
Material test with power and speed on an offcut, aim: dark, but not deeply charred.
Interval Test for the line interval.
Engrave a small section of the photo. xTool recommends the eye area for this, because details are easiest to judge there.
Only then the whole image.

Wood and slate: exactly the opposite

On wood, the burned spot turns dark. So the photo can stay as it is: dark areas of the image get many dots.

On slate, dark granite and dark anodised aluminium it is the other way round. The laser lightens the surface. Without adjustment you get a negative. So you invert the image:

LightBurn: In the layer settings of the image, enable “Negative Image”. LightBurn expressly names slate and glass for this. With the “Preview Invert” switch you can see in the preview how it will look on a dark background.
xTool Studio: Select the image and switch on “Invert color”. xTool advises: invert first, then adjust the grey values. If the material turns darker when lasered, do not invert.

After lasering slate, wipe off the dust. A few drops of oil darken the stone and raise the contrast.

Common mistakes

Mistake	Cause	Remedy
Image too dark, face becomes a blob	too much power, line interval too small, photo not lightened	Lighten midtones, increase interval, reduce power or move faster
muddy, no detail	focus blurred, dots run together, photo too soft	Check focus, sharpen slightly, test Dot Width Correction
pale, washed out	too little energy, interval too large, low contrast in the photo	Increase contrast, increase power, reduce interval
Stripes across the image	gaps between lines, grain, mechanics	Interval Test, calmer wood, see Uneven engraving
dark edges on the left and right	no overscan	Enable overscanning, see Uneven engraving
yellow-brown haze around the image	smoke and resin	Air assist, masking, see Burn marks
Negative on slate	image not inverted	Enable Negative Image or Invert color

Summary

Choose light, calm wood, slate or dark anodised aluminium.
Crop the photo, calm the background, lighten the midtones, sharpen slightly.
Line interval to suit the laser dot, usually 0.08 to 0.1 mm for diode lasers, confirmed with an Interval Test.
Jarvis as the starting mode, test greyscale on your machine.
Invert the image on slate and dark aluminium.
Always engrave a small section on an offcut first.

Next: Laser parameters, LightBurn and Engraving, cutting, marking.