LPI.

The number of halftone cells per inch, which CADlink defines as the halftone frequency. It trades against shades: at 300 DPI a 60 LPI cell is 5 × 5 pixels and holds 25 shades, while 20 LPI gives a 15 × 15 cell and 225. In screen printing the frequency has to match the mesh. Chromaline multiplies LPI by 4.5 for the lowest suitable mesh count, so 45 LPI wants about 202, and warns that mesh opens by 4-8% when it is tensioned. UltraSeps outputs simulated process at 55 LPI and 26 degrees on 280-305 mesh for the top colours, and suggests 45-50 LPI on 230 mesh for manual presses. On a print-on-demand upload LPI is rarely the seller's setting; the RIP applies it. It matters when a file arrives already halftoned: dots baked in at one frequency and re-screened at another produce moiré, the rippled pattern Chromaline traces to a mesh and line count that do not agree. Pick a frequency too fine for the mesh and the small highlight dots do not hold on the screen and wash out before the first print.