An arrangement of dots used to simulate a traditional halftone on a digital printer. Because an imagesetter can only produce black dots, it must simulate shades of grey by turning some of the dots in the cell on or off. If half the dots are on, it appears to be 50% grey. Since PostScript can handle 256 shades of greay, the optimal halftone cell is 8 x 8 (8 dots wide times 8 cells high equals 256 dots total). Therefore, the optimal line screen for a given printer is its dpi divided by 8 (e.g. 600 dpi can produce a halftone pattern 75 lines per inch). Unfortunately, this simple formula is complicated by arcane matters beyond the scope of this document.