LightBurn Image Mode and Dithering for Photos
Photo engraving is one of the most satisfying things a CO2 laser can do, and one of the easiest to get almost right. The image looks great on the screen, the job runs for a long time, and the piece comes off the bed a little dark, a little muddy, or a little flat.
LightBurn's image mode is doing a lot of work in that job. It has to turn a photograph into something a laser can actually burn, one scan line at a time. If you understand a few choices in that mode, you can stop guessing and start testing in a tighter range.
How LightBurn Engraves a Photo
A CO2 laser does not print gray ink. It either fires or it does not, or it varies power as it scans, depending on the mode. A photograph is full of soft tones. Image mode is the bridge between those two things.
The bitmap is opened or imported and stays in Image Mode in the Cuts / Layers Window — you do not set a photo to Fill or Line. LightBurn then scans it in Image Mode. Line Interval / DPI, speed, power, and the image mode all change how those tones show up on wood, leather, or a coated material. The material matters as much as the software. A photo that looks beautiful on maple may disappear on dark walnut, or blow out on a soft basswood ornament.
Choosing a LightBurn Image Mode
LightBurn includes several ways to render an image, including dithering options and a grayscale option. Dithering uses a pattern of dots, usually at a more consistent power, to suggest lighter and darker areas. Grayscale varies power between Min Power and Max Power as it scans.
Neither one is "the best" for every job. Dithered modes such as Jarvis, Stucki, Atkinson, and Dither (error-diffusion dithering, often described as Floyd-Steinberg) are popular for photos on wood because they can keep detail without turning the whole image into a dark smear. Different dither algorithms distribute the dots differently, so the same photo can look a little sharper, a little softer, or a little grainier depending on the choice.
On a CO2 laser, that often shows up as a change in depth more than a smooth photographic tone, which is why LightBurn describes Grayscale as a variable-depth or 3D approach. It can work on some materials, and it can look washed out or overly dark on others. For a photo-like image on wood, start with a dithered mode and only move to Grayscale if you are intentionally chasing depth. The only honest way to choose is to run a small test tile of the same image, in the same size range, on the same material.
Do not copy a dpi, interval, or mode from a forum post and expect it to be universal. Those numbers were true for that person's machine, lens, and material that day.
Dithering vs Grayscale
A simple way to think about it: dithering is a pattern of marks that your eye blends into tone. Grayscale is a power curve. If a dithered photo looks too dark, you may need a lighter image, a faster speed, lower power, or a different dither, not just "more contrast" in every direction. If a grayscale photo looks muddy, the material may not have a wide enough burn range, or the power span may be too tight or too hot.
Adjust the image before you keep turning the laser up. A slightly flattened, well-sized photo often engraves better than a high-contrast phone snapshot. Watch the highlights. Once they are gone on wood, they are gone.
Preparing Artwork for Photo Engraving
Start with a reasonably sharp image at a size close to the finished engrave. A tiny photo stretched across a large plaque will look soft no matter which dither you pick. Crop out busy backgrounds when you can. On wood, a little contrast helps, but crushing the blacks will fill in as a dark blob.
We often engrave a small test, not the full portrait, when we try a new material. A face, a patch of sky, and a dark area are enough to tell you if the mode is working. If you are running on pale wood, a mask can keep smoke stain from dulling the unburned surface around the photo, which otherwise makes the whole piece look older than it is.
Set focus carefully. Photo fills are unforgiving of an unlevel bed or a bowed board, because a soft area reads as a bad image mode. If one side of the photo is crisp and the other is fuzzy, check bed level and focus before you change the dither.
In LightBurn, also confirm Negative Image is only on if you actually want the image inverted, and that you are not stacking a second pass on a layer you forgot was enabled.
Test, Don't Guess
Our process for a new photo product looks like this:
Prepare a clean, correctly sized image.
Place a scrap of the real material, masked if the final will be masked, and set focus on that surface.
Run a small test in two or three image modes at the same interval and speed.
Pick the one that holds detail in both the lights and the darks.
Adjust speed or power in small steps, or adjust the image, not both at once.
Save the winner in the material library with the material and mode in the name.
Photo engraving rewards patience more than it rewards a magic number. The LightBurn image mode is powerful, but it cannot invent detail that is not in the file, and it cannot save a piece that was out of focus. Give it a good image, a tested mode, and a true surface, and this is one of the jobs that makes a CO2 laser feel like more than a cutter.
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