FM screening is a halftone process based on pseudo-random distribution of halftone dots, using frequency modulation (FM) to change the density of dots according to the gray level desired. Traditional amplitude modulation (AM) halftone screening is based on a geometric and fixed spacing of dots, which vary in size depending on the tone color. The stochastic screening or FM screening instead uses a fixed size of dots and a distribution density that varies depending on the color’s tone.
FM Screening requires the use of a “squared print resolution”. Set the Print Resolution to 720 x 720 or 1440 x 1440; some printer models offer limited squared resolutions. Use of a non squared resolution, such as 1440 x 720, will cause unexpected, un controllable results.
The use of FM takes requires a print shop to test various microns and gamma settings against a variety of mesh counts and exposure times and techniques to establish best result. Most printers do not take the proper time and efforts to discover what is best for them. In this case choose AM halftone. AM halftones can be printed using any print resolution squared or non squared.