Computer-To-Plate technology has allowed more printers to utilizing a different technique for printing halftones known as Frequency Modulation (FM) screening, or stochastic printing. However, conventional screening, or Amplitude Modulation (AM), is certainly not obsolete, especially when higher line screens of 175 to 200 are used in halftone and four color process printing.

The best way to define stochastic printing is to compare it to conventional printing.

In conventional printing, images are printed using grid-like screens that separate the image into evenly space dots that are larger in size in the darker areas and smaller in size in the light areas. In four color process printing, separate screens are used to reproduce each of the four colors, black, cyan, magenta and yellow.

In stochastic printing, images are printed by dots spread randomly throughout the image area. The dots are not equally spaced and aligned in a row or grid and they vary according to the tonal value to be reproduced. The lighter areas have few dots, the darker areas have more dots.

There are significant differences, advantages and disadvantages of both stochastic and conventional screening. Printing with stochastic screening offers the advantages of more detail, less ink on the sheet, no moiré pattern, increase tonal values, crisper fine lines and small type and cleaner reverses. Conventional screens have the advantages of greater latitude of changing color density on press, more forgiving halftone reproduction, better printing of large amounts of ink on paper and better production of one and two color printing.

The charts below offer a comparative review of the advantages and disadvantages of each screening technique:

Stochastic Printing
Advantages More detail Less ink on the sheet Film of ink more evenly distributed on sheet More light reflects back to the eye from the printed image Ink dries faster on the sheet Eliminates moiré patterns Easier to print more than 4 colors in one pass Better for touch plates Eliminates sawtooth edges in screens Best for printing textiles and other patterned images Shadows are more open and details are crisper Precise plate production More consistency from start of printing to end of printing Simulates continuous tone photographs Fine lines, small type and reverses print better	Disadvantages Can reproduce too much detail; grain of image’s photographic film can become visible, imperfection in flesh tones are more visible Holding a small dot is a great challenge on press Very unforgiving on press Tighter controls have to be implemented 20% more dot gain than conventional Proofing is difficult

Conventional Printing
Advantages Greatest latitude of modifying color on press Bigger dots more forgiving on press Ability to put larger amounts of ink on paper Metallic or opaque ink halftones have larger impact When comparing 175 to 200 line screen to stochastic there is little difference Works better for one and two color printing Works better for skin tones	Disadvantages Moire patterns Sawtooth screens Fine lines, small type and reverses can be problematic More difficult to register touch plates and additional colors beyond four colors