Harlequin Precision Screening

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

Harlequin Precision Screening is adaptive; that is, it finds a combination of frequencies and angles for a set of screens suitable for color work that, in decreasing order of importance:

• is sufficiently close to the angles required for there to be no moiré, or interference effects between color separations;
• keeps the frequencies of separations close enough to each other that there are no interference effects, except for the yellow separation which is treated specially;
• keeps the frequencies close enough to the frequency requested;
• generates enough distinct levels of gray to produce smooth vignettes even when the ratio of screen ruling to resolution is small.

The parameters to control HPS are mostly concerned with what sufficiently close or close enough mean in this context.

Remember that system parameters are global: their effect is maintained throughout one invocation of the RIP. Use of system parameters is therefore discouraged in page features or other job preambles unless the same parameters are consistently present for all jobs. However, some screening parameters are exceptions to this, including the HPS parameters AccurateScreens and ScreenAngles, which, though system parameters, are automatically reverted to their defaults in the RIP server loop (that is, between jobs). This avoids problems with generating HPS versions of default screens when they are likely not used. (The other exceptions are mainly the Override parameters, and this is always noted in the parameter documentation.)