Laser programs use four or five names for what is really one or two numbers. This page defines each term and shows how they convert.
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Try Vextrify freeDPI means dots per inch: how many dots the laser writes along one inch. More DPI means smaller steps between lines or dots. It is a measure of spacing, not of quality. A higher number does not guarantee a better engraving, because the beam has a physical size, and steps much smaller than the beam only overlap.
Line interval is the distance between two neighbouring engraved lines, usually in mm. It is the inverse of DPI: interval in mm is 25.4 divided by DPI. So 254 DPI is 0.1 mm and 127 DPI is 0.2 mm. If the interval is smaller than the laser's spot, neighbouring lines overlap and the tones get darker. If it is larger, gaps appear between the lines.
Dot density is the loose, general term for how tightly the dots or lines are packed; it is not a single unit. Lines per mm or lines per cm count the same thing from the other side: 10 lines per mm is an interval of 0.1 mm, because the interval is 1 divided by the line count. When you see density quoted, check whether it is a count per length or a distance, since the two move in opposite directions.
LightBurn and RDWorks-style software expose this as a line interval or as DPI, depending on the setting and the layer type. Because the names differ, compare the unit rather than the label: a value in mm is an interval, a value in DPI or in lines per length is a density. Also keep one thing in mind for dithered images: LightBurn's Pass-Through sends an image that was already processed without dithering it again, and a pre-dithered image has to be engraved at the same DPI it was made for. Otherwise the dots are resampled.
Photo Studio exports a PNG at the DPI and output size you choose, with a live preview, so the density is set deliberately rather than inherited. There is no universal figure to pick: speed, power and spacing depend on the machine and the material, so they come from a material test grid on scrap. Dot duration, the time each dot is burned, is a separate setting with its own page.
Divide 25.4 by the DPI. The result is the line interval in mm, so 254 DPI is 0.1 mm and 127 DPI is 0.2 mm.
No. A line interval smaller than the laser's spot makes neighbouring lines overlap, which darkens the tones. The right spacing depends on your machine and material and comes from a test grid.
Dot density is the general term for how tightly dots or lines are packed. DPI is one way to measure it. Line interval measures it as a distance instead.
The dots are placed for one specific resolution. Engraving at a different DPI resamples them, which blurs the pattern and shifts the tones.