Although FM screening has been around since the mid-1960s, it didn't really catch on until the late 1990s.
FM (Frequency Modulated, also called "Stochastic") screens consist of irregularly spaced, same-sized micro dots. Traditional AM (Amplitude Modulated) screens consist of larger, regularly spaced, variable-sized dots. With FM screening, tone densities are varied by placing different numbers of small dots within a given area rather than by changing the sizes of a fixed number of dots as in conventional AM screening. The effect is that the dots seem to disappear, resulting in unsurpassed clarity and detail, especially in images of fabrics, jewelry, automobiles and skin tones. FM screening also eliminates moire patterning, rosettes and colour shifts which can form in halftones.
The roadblock to successful FM screening was not being able to consistently hold the fine dots on press. The breakthrough came with the introduction of digital workflow and computer-to-plate (CTP) technology. CTP bypasses the capricious nature of film-based workflows and has proven to
files are RIPed directly to a device that uses a laser beam to image the plates. This results in sharper dots, improved registration and reduced dot gain. It also helps ensure quality when printing more than four colours -- for example, touch plates, knock-outs, screen tints, hexachrome -- because there are no screen angles to cause moire.
Colour innovations uses the latest generation plate-setters which can hold a 1% dot. That makes a big difference in high-end colour work such as brochures, catalogues, annual reports, POP,
and packaging.
The key to successful FM screening is having pre-press and printing under one roof. It is vital
that the correct dot gain compensation curve is developed by extensive testing for each press on coated gloss, matte coated and offset stocks. FM screening is an excellent technology but implementing it requires discipline.
