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Harlequin Dispersed Screening for the RTI RIP or Workflow

With the Harlequin Dispersed Screening Option (HDS Stochastic / FM Screening), smaller dots intelligently placed provide improved image detail, cleaner colors, and significant ink savings. HDS creates reproductions with increased sharpness over conventional screening methods and offers complete freedom from both object and cross-screen moiré. It is ideal for reproducing subjects for which object moiré is a problem (such as scenes with fabric, venetian blinds or picket fences) and where detailed reproduction is required.

The main advantages of using HDS are that it produces no moiré, it has better definition than conventional screening, and registration is less critical. HDS also has a visually pleasing screen structure and is generally more printable than other FM screens. Finally, it should be noted that HDS is intended for use with a wide range of printing processes. Instead of using a fixed shaped dot structure, HDS uses irregular clusters of pixels to form an irregular HDS dot. The distribution of these dots or clusters through the screen is what gives HDS its characteristics.

Frequency Modulated (FM) screening technology differs significantly from conventional halftone screening techniques. Conventional methods place dots in a grid pattern to reproduce a continuous tone image. Shades of tone are simulated by enlarging or reducing the dot size in a particular area of an image. With frequency modulated screening, the dots are dispersed in a less structured manner. Varying shades are created by the irregular frequency, or dispersal, of the screening dots.


While the latest RTI Harlequin RIP and HDS Stochastic Screening option include the ability to output Stochastic Screens to every color, users can also now choose to output using a newly developed Stochastic Yellow feature. This feature allows users to output Cyan, Magenta, Black and any spot colors using Harlequin's conventional AM screen sets while also applying a stochastic screen to the Yellow. For the first time ever users with the HDS option can have one page setup configured to output a stochastic screen on just the Yellow plate while outputting CMYK and Spot Color data using an AM screen set. HDS Stochastic Yellow supports HDS Super Fine, Fine, Medium, Coarse and Super Coarse dot shapes.


Stochastic Screening now includes 5 additional levels of extended coarseness. This means users can fine tune HDS to suit the reproduction process by selecting one of five dot varieties (Super Fine, Fine, Medium, Coarse, Super Coarse, 2X Super 2X Fine, 2X Fine, 2X Medium, 2X Coarse, and 2X Super Coarse). In general, the higher the quality of the entire printing process the smaller the HDS dot that can be used. Films and plates produced using HDS are reproduced easily using a wide variety of platesetting and printing processes. Exceptional results have been obtained with HDS on newsprint with web press equipment, on high-quality coated papers with commercial sheet-fed presses, and using direct output methods such as digital proofers.

5 Levels of Extended Coarseness: In addition to the standard HDS Super Coarse, HDS Coarse, HDS Medium, HDS Fine and HDS Super Fine screening (shown below), customers using HDS will now receive five additional coarseness levels (2X Super 2X Fine, 2X Fine, 2X Medium, 2X Coarse, and 2X Super Coarse). These additional dot selections can be used to adjust the coarseness of a job without having to lower the resolution. The sample image shows Magenta at the standard HDS Super Coarse and the Cyan at HDS Super Coarse Extended Range.
HDS Super Coarse: HDS Super Coarse uses a larger structure to increase printability and the capability to retain highlighted areas of an image. It is suitable for use on mid to low-range imagesetters or platesetters with resolutions between 1000 and 1600 dpi.
HDS Coarse: HDS Coarse makes use of somewhat larger structures to increase printability and is best selected on presses which cannot hold very fine detail such as in high speed web printing.
HDS Medium: HDS Medium offers a slightly larger dot structure in the midtone range. It may be used in intermediate commercial and publications printing, either sheetfed or web.
HDS Fine: HDS Fine produces extremely smooth grain-free results and has the finest structure of any HDS setting. It is intended for use with high quality output devices capable of recording single isolated laser spots on separations.
HDS Super Fine: Developed for use on low resolution output devices which deliver high quality output without compromising speed.

Below is a table with the spot sizes in microns for the different HDS models and different output resolutions using a 20% HDS screen.

HDS Super Coarse Sample
HDS Coarse Sample
HDS Medium Sample
HDS Fine Sample
HDS Super Fine Sample
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