Seamless screening

 This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.

Some printing situations require a single raster to be produced that will be printed many times with no gaps between the iterations in order to produce a very long continuous graphic (e.g., wall coverings, textiles, laminate flooring, etc.), or to support staggered imposition, where single labels, etc. must continue across the join. If screening is being performed in Harlequin, that screening is likely to need to be seamless to avoid visible artifacts (such as “zip-lines”) at the joins.

Enabling seamless screening ensures that the screening at the left side of the raster will connect seamlessly with the screening at the right side of the raster.

Seamless screening can be applied to any screen type that is handled by the Harlequin core; using spot functions, thresholds or tile-based screens. It cannot be applied to screening applied using modular screening.

To make the screen seamless some screen cells are distorted slightly, making them slightly wider or narrower. Seamless screening is managed using the ScreenXSeamless system parameter, which may take one of the following values:

• false: no action (default)
• true: seamless, using widening or narrowing screen cells, selected on the basis of minimal distortion.
• 1: seamless, widening screen cells
• -1: seamless, narrowing screen cells

<< /ScreenXSeamless -1 >> setsystemparams

Different screening types react better to widening cells or to narrowing. In general, a more dispersed screen will usually benefit from narrowing the cells, while other screen types are less sensitive. The most dispersed screens for example, those commonly used for inkjet presses may not suffer from visible artifacts at joins in the first place, in which case the distortion applied by enabling seamless screening may even reduce output quality. This means that seamless screening is most likely to be of value on flexo sleeves, gravure cylinders or rotary screen presses, or on digital presses that require a more clustered screen pattern for some reason.