Stochastic screening

Stochastic screening is a type of digital halftone screening which varies the pattern of dots while keeping the size of the dots constant. In contrast, conventional halftone screening varies the size of the dots while keeping their frequency per line constant.

Advantages

• Eliminates the necessity of worrying about screen angles when printing multiple colors; the irregular pattern of dots eliminates the interference of screen lines that causes moiré.
• Enables low resolution output devices to achieve 256 levels of grey and hence may reduce the time required for ripping. On the printing side, the pseudo-random dot placement eliminates screen angle and subject moiré.
• Delivers more consistent on-press color since the small dots minimize mechanical dot gain as solid ink density naturally varies through the press run.

Disadvantages

• Tiny dot size creates difficulties in proofing and platemaking, but the advantages of stochastic screening are engendering the desire to quickly solve these somewhat minute problems.

Stochastic screening is available from most prepress equipment vendors. It is particularly suitable for the color printing of complicated images involving complex textures such as that of woven fabrics such as tweeds and silks, repeating backgrounds, and other geometric shapes that tend to cause interference/moiré problems when printed using conventional screens. It is being used in day-to-day printing for projects ranging from telephone directories to fine art reproductions.

References

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