If you've engraved a photo and it came out flat, overly dark, or just "off" in a way you can't quite name, the problem almost certainly isn't your machine, your settings, or your material. It's that the photo was never converted into something a laser can actually engrave — a step called dithering, and it's the single most important concept in laser photo preparation that nobody explains clearly.
The core problem: a laser only has two states
A photo on your screen has smooth gradients — thousands of subtle shades between pure black and pure white. A laser doesn't work that way. At any given spot, it either fires or it doesn't. There's no "fire at 50% strength" setting that reliably produces a true middle gray on most materials. So the question becomes: how do you represent a photo full of soft grays using only a laser that can burn or not burn?
The answer: fool the eye with dots, not gray
Dithering solves this the same way newspaper photos have worked for over a hundred years, long before digital screens existed: instead of true gray, you use a dense pattern of tiny black dots. Look closely and it's just dots and empty space. Look at it normally — from a foot or two away — and your eye blends them into the impression of gray. Denser dots read as darker; sparser dots read as lighter. The photo was never actually gray at all; your eye is doing the work.
Skip this step and feed a laser a raw grayscale photo, and most software makes a crude guess at translating each shade into "burn" or "don't burn" using a flat threshold — which is exactly what produces that flat, muddy, posterized look, where all the subtlety in the original photo collapses into a few harsh blocks of black and white.
Not all dithering looks the same — the three common patterns
Floyd-Steinberg is the most common general-purpose choice. It works by "spreading" the rounding error from each pixel onto its neighbors as it processes the image, which produces a fine, somewhat organic-looking dot pattern that handles smooth gradients and general photos well. For most portraits and typical photos, this is a solid default.
Atkinson is a lighter-touch variant — it spreads less error to neighboring pixels, which tends to preserve more contrast and produces a slightly cleaner, higher-contrast look. It can work particularly well on images where you want the engraving to read as more graphic and less soft.
Bayer (ordered dithering) uses a fixed, repeating grid pattern instead of the more organic error-spreading approach. It produces a distinctly geometric, uniform texture, which some materials and some design styles suit better than the more random-looking patterns above — it can also be more forgiving on materials where a very fine, irregular dot pattern doesn't come out cleanly.
Which one should you use?
Genuinely, this depends on your specific material, your machine's settings, and even the photo itself — there's no single universally "best" choice, which is exactly why comparing them side by side on your actual image before committing to material is worth the extra thirty seconds. A photo with lots of smooth skin tones might favor Floyd-Steinberg; a high-contrast graphic image might look great with Atkinson or Bayer instead.
Contrast still matters, even with good dithering
Dithering handles the "how do I represent gray" problem, but it can't fix a photo that's fundamentally too flat or too dark to begin with. Boosting contrast before dithering — so the image has genuine bright highlights and dark shadows, not just a narrow band of mid-tones — gives the dithering algorithm more to work with, and usually produces a noticeably cleaner, more readable engraving.
The short version
If your engraved photos have looked muddy, the fix almost certainly isn't more power or a different speed setting — it's giving the laser a properly dithered image in the first place. Once you understand that a laser engraving a photo is really just a very precise arrangement of dots pretending to be gray, the rest of the process starts making a lot more sense.