The line interval is the spacing between horizontal lines in a bitmap engraving. (You could go further to dial it in, but since the Snapmaker’s default minimum step is 0.1 mm, and the stated dimensional accuracy is 0.2 mm, it doesn’t appear to be useful.

This allowed me to establish 7.9 mm as my optimal focal length. I found that my optimal focal length occurred between 7 and 8 mm, and I then tested between 7.0 and 8.0 mm at 0.1 mm increments (by setting the number of increments to 10). I tested my laser on cardstock paper in 1 mm increments from 5 to 10 mm at first and kept power constant at 75%. It also allows you to test at a user specified speed. It allows you to vary Z axis and power over a user defined number of increments. Lightburn has a focus test under Tools>Focus Test which allows you to find your optimal focal length. I have documented the process so that others can enjoy the full capabilities of Lightburn and the Snapmaker laser.

The greyscale algorithm is advanced and depends on a well-calibrated machine to produce a good quality image. I spent a lot of time going through a calibration process to enable me to laser engrave using Lightburn’s greyscale image function. Lightburn Calibration for Greyscale Engraving

Lightburn camera calibration locations