When you engrave a photo, your software has to turn continuous tones into something a laser can fire: dots. Dithering and grayscale are the two ways to do that - and choosing wrong is the most common reason an engrave looks bad.
What dithering does
Dithering represents shades using patterns of on/off dots (like a newspaper photo). It is forgiving, works on most lasers including diode machines, and is usually the right choice for photos and organic images. Floyd-Steinberg is a common, reliable pattern.
What grayscale does
Grayscale varies laser power to create true shades of gray. It can look smoother on gradients and clean illustrations - but only on materials and machines that reproduce power variation consistently. On the wrong material it turns to mush.
Let the material decide
Even-grained light woods and coated metals handle grayscale better; busy grain and forgiving materials favor dithering. When unsure, dither - it fails more gracefully. Always test both on scrap of the exact material.
FAQ
Which is better for diode lasers? Dithering - most diode setups reproduce dithered patterns more reliably than smooth grayscale.
Can I preview before cutting? Yes - a prep tool like EngravePrep lets you compare dithering and grayscale before you burn material.
Compare both on your photo. Try EngravePrep free.
Related reading: Photo engraving prep and settings · Multilayer laser art from one image.