For high end colour printing applications, there’s a traditional divide between contone and halftone output. Contone prints on photographic paper are widely regarded as the benchmark for image quality, longevity, colour fidelity and competitive cost; whilst halftone methods have become something of the default for text, line art and convenience.
Continuous tone photographic images contain an infinite range of colours, and no dot structure. They’re produced via a wet chemical process that uses the reaction of light on substances in photo-sensitive paper to achieve incredibly smooth images. This is wonderful for pictorial graphics and photographs, but less successful for text, which becomes blurry and illegible at small point sizes.
Halftoning was developed in the nineteenth century as a way to reproduce photographs in newspapers, it reduces shades to patterns of dots of different sizes, shapes or spacing which could be printed with a single ink. At that time, the majority of printing was for words on paper – black text on a (white) background. Halftones simulate continuous tone images by optical illusion : the human eye blends the dots into smooth tones.
For a single colour ink (B&W images), halftoning is relatively straightforward. Colour printing with multiple screens is more complicated, as it’s important to keep the different coloured dots close together to fool the eye into seeing different colours. However, overlaying dots of different arrangements may cause unwanted visual effects like moire patterns. Positioning the colours at different angles reduces this problem, and groups the dots into characteristic rosettes.
Digital halftoning was introduced during the 1980s in new imagesetters with PostScript RIPs, capable of handling all page elements (photographs, type and graphics) at higher resolutions. Thirty years later, PostScript technology has become industry standard, both accessible and affordable : the problem of printing words and images on the same page still remains.
The our unique production process features new, photonic technology to print digitally on standard photographic roll paper. LumeJet's Digital Print Head achieves ultra high resolutions, pinpoint accuracy with all the benefits of photo paper – true contone images. So for the first time, it’s possible to combine photographic images, fine vector artwork and pin-sharp text (right down to one point size, in colour, reversed out of a black background) on the same page.