ID Tip: Offset Lithography or Digital Press?

Like offset lithography, digital press (DP) is used in production scale printing. A digital press uses electrophotographic technology, with either dry toner or liquid toner as its colorant. Unlike offset lithography, it does not require a physical master, which makes it a versatile, high-speed, print-on-demand production printer. In spite of these two technologies being so different, prints produced by them may be mistaken for one another at first glance: both technologies may use coated or uncoated, matte or glossy papers, and both frequently produce rosette dot patterns –amplitude modulated (AM) screens. In the case of offset lithography and dry toner DP, patterns of irregular appearance –frequency modulated (FM) screening are also an option. So how can we tell them apart?

Rosette dot pattern (AM screening)	Irregular dot pattern (FM screening)

Regardless of the printing dot pattern, under magnification (25-50x) the dots have distinctive characteristics due to the way the colorant is laid on the paper. In offset lithography, the dots have rough edges; liquid toner DP produces smooth-edged dots; and dry toner DP produces dots with rough edges and a dusty appearance. Another hint, an image printed with dry toner produces a relief on the paper that is usually easy to feel, while liquid toner and offset colorants lay flat enough that they are difficult to feel. Check out our Print Comparison Tool [2] for more examples and information.

Offset Lithography: dots with rough edges in a rosette pattern	Dry Toner DP: dots with dusty appearance in a rosette pattern
Liquid Toner DP: dots with smooth edges in a rosette pattern

Production Printing Summary