MultiDot – the new AM screening concept Screening technology let reproduce continuous tone images using bilevel printing method (as f.e. offset). Some properties of human eye allows the correct reception of the continuous tone image. One have to remember, that tonal value (caused by surface covered by printing elements only) existing on the printing plate is not the same as the one present on the printout. In offset printing technology the difference between tonal value on the printing plate and on the printout is provoked by two different phenomenons: one is the Dot Gain, while the other is caused by driving the ink out by dampening solution. The Dot Gain effect has 3 main reasons: · spilling out of the ink on the printed surface, · deformation of transfer medium (f.e. offset blanket) - present only when indirect printing technology is in use · “shadow” of the printing ink layer. ... and is well defined and known. The mutual (the ink and the water/dampening solution) influence is very difficult to predict using mathematic formulas. We can observe, that (because of the Dot Gain effect) there are some areas not covered by ink, but absorbing the light as they would be – so it can be a base for some ink saving – if the effect would be used properly. However the FM screening has significant DotGain effect (so ink saving should be noticeable), it demonstrates lot of disadvantages: less print stability, unevenly flat areas and many, many others. To fulfill some expectations the new AM screening was developed (and patented). It was named MultiDot and is based on multi-cluster principle, where – what’s important – single clusters have different size and shape. Optimal shape and tonal function caused, that newly developed screening concept let the user receive stable, rich in details and Moire free images with significant ink-saving capabilities. The other aspect of using MultiDot screening structure is to prevent prints against illegal copying and allowing the user to confirm (or deny) the authenticity of certain printouts or goods – this functionality is called MultiDot Security and will be a subject of another article.