The amount of dots in an inch of a halftone is determined by the LPI, also known as line screen. The higher the LPI, the more dots there are per inch. A higher LPI means the dots are smaller and less noticeable. Letterpress printers typically use between 85-133 LPI for their halftones. We find that 100 LPI is a good choice for all plate types and is the default we apply if you don’t specify.