Laser test card generator

The test card tool in the app makes three kinds of card. Each one is a 1-bit file laid out in millimetres, so it engraves at a known physical size. Pick the material first: for materials that mark light, such as black slate, the card is inverted the same way a photo would be.

• DPI card: a row of filled patches, one per DPI. By default it tests 181, 203, 254, 318, 363, 423 and 508 DPI, and you can change the list. The card also carries fine lines and small text, so you see the narrowest stroke your beam holds and the smallest lettering that stays legible.
• Power and speed grid: a grid of cells where power changes across the columns and speed changes down the rows. You choose the minimum, maximum and number of steps for each, in mm/min or mm/s. Each cell carries its power and speed as engraved labels. An optional tone ladder adds a row of grey patches from 0 to 100 percent, dithered with the method you pick.
• Dither comparison: your own photo, engraved as a strip of tiles, one per dither you select, at the tile width you set. It is the honest way to choose a dither, because it shows how each pattern looks after your laser and your material have had their say.

Every row of the file is one laser pass. The card is drawn at a high file resolution (you choose 1016, 1270, 2032 or 2540 DPI), and each patch burns one row every so many rows, so it reproduces that patch's line interval exactly. That is why the file DPI and the tested DPI are two different settings.

Burn the whole card at one power and speed. The best DPI is the lowest one whose patch looks solid with no visible lines. Higher DPIs only overlap the lines and over-burn: the patch gets darker, but detail in a photo gets muddy and the job takes longer. Then set that DPI in the laser DPI calculator or straight in One Click.

In your laser software, import the card so its own line interval is kept: use pass-through, or set the line interval to the file's. The .lbrn2 project from the app already does this for you.

The app does not suggest power or speed values, because they depend on your machine, lens, focus and the exact blank. The grid lets you find them yourself in one burn instead of ten. Look for the cell where the mark is as dark (or as light, on inverted materials) as you want without scorching the edges or melting the surface.

You get the card as an image, a table of every cell's power and speed, and a settings CSV. A .lbrn2 project holds a single image layer, so it cannot give each cell its own power and speed. For that the app also exports an SVG with one colour layer per cell, with the labels on their own layer, when the grid is small enough: you import the SVG and enter each layer's power and speed from the table. Very large grids skip the layered SVG and say why.

Two blanks that look the same can burn differently. A new batch of slate, a different plywood sheet or a tumbler with a different coating can each shift the right settings. A test card on an offcut costs a few minutes and saves the real piece.

The dither comparison is the most useful card for photos. Our Ultra dither usually holds the most tone, but on rough or grainy surfaces such as cork a smoother error diffusion can read better. Seeing them side by side on the real material settles it.