Scitex Class Screen S/W Version 7 Overview

J. Bal
October 31, 1994

Overview
Conventional Screen
Geometric Dot
High Definition Screen
FULLTone
Getting Started
Activating Scitex Class Screen
Setting Screening Parameters

Overview

The new hardware-based CreoScitex Class Screen is available for the Dolev 200, Dolev 400 and Dolev 800 imagesetters.

The CreoScitex Class Screen is enabled by a new VLSI card with an expansion board. Once this card is installed, you can use either the regular screening functions or the CreoScitex Class Screen functions. To expose, set the required parameters in the used Plotter format (to activate the CreoScitex Class Screen function, toggle the Class Screen field to Yes).

CreoScitex Class Screen produces the following screening benefits:

Minimal or no artifacts, noise, or grain in single separations.

Reduced moire effect between separations.

Smoother dot fringe.

Ability to apply the following new screening features:

Geometric dot shape. Note: This new feature is also available in regular screening.

High definition screening in relatively low resolutions. For example: 600 LPI (lines per inch) screen ruling at resolution 140.

FULLTone screening (which is similar to random or stochastic screening).

Relatively lower resolution exposures using a standard mesh.

Conventional Screen

Scitex Class Screen still supports all the conventional dot shapes (i.e, Round, Diamond, Square, Composite and Gravure).

The conventional dot shapes have an improved, sharper, and crisper appearance, and benefit from:

Less noise.

A smoother appearance.

Higher dot edge definition.

Future Figure:Conventional Dots

Geometric Dot

Geometric Dot is a new shape supplied with this software version. It can be used either with CreoScitex Class Screen (i.e., Class Screen:Yes) or with regular screen (i.e., Class Screen:No).

The geometric dot changes based on the area that it covers:

Separate round cells in the highlight areas.

Connected ellipses in the lower midtone areas (left figure).

Lines or bars in the higher shadow areas (middle figure).

Inverted elliptical-shaped bars in the darkest shadow areas (right figure).

Future Figure: Geometric Dot

Using geometric dots produces the following benefits:

No rosette patterns on the printed media.

Elimination of yellow moiré effect in red and green areas.

Enables multi-color printing.

Enhanced details with a sharper, crisper appearance.
High quality with low mesh values. This makes this dot especially suitable for newspapers and magazines.

High Definition Screen

High Definition is a new CreoScitex Class Screen feature that enables a screen ruling of up to 600 LPI (lines per inch).

High definition screening uses the Dupli function to control the highlight and shadow areas by balancing dot frequency and size. It is ideal for fine-art reproduction and other high-fidelity work.

Future Figure:High Definition screen

FULLTone

FULLTone is similar to random (stochastic) screening.

Conventional screening places dots in fixed positions based on screen ruling.

Random screening allows dot size and placement to vary, depending upon the dot percentage of the image area that it covers.

FULLTone requires no extra computing time, since screening is performed on-the-fly. This feature and the production high-quality images in lower resolutions makes FULLTone a relatively fast screening option. Processing and exposure time is reduced and less storage space is required.

Future Figure: FULLTone screen

FULLTone provides the following benefits:

Enables the production of higher-quality results using lower resolutions.

Enables using scanning resolutions 10% - 20% lower, to achieve the same high quality. The lower-resolution image files are smaller and therefore require less processing time, less exposure time, and less storage space.

No rosette patterns on the printed media.

No moire pattern between separations.

Subject moire is eliminated (i.e., no interference between screen patterns and subject patterns).

Details are enhanced and have a sharper, crisper appearance.
Enables multi-color printing.

Getting Started

Important Note:
CreoScitex Class Screening can only be applied after you have installed a CreoScitex Class Screen VLSI plug-in card. In all other cases, do not expose using a Plotter format in which the Class Screen field is set to Yes. If you do, an appropriate message is displayed.

Perform the following to implement the new CreoScitex Class Screen feature:

Install the relevant Whisper Software version.

Make sure that the CreoScitex Class Screen VLSI card is installed in the Whisper cabinet.

Expose your image using CreoScitex defined System Plotter formats, or prepare your Class Screen settings in User Plotter formats as described below.

Activating Scitex Class Screen

Overview
Class Screen
Dot Type
Type of Fulltone [toggle field; by default Normal]
Top Quality

Overview

CreoScitex Class Screen is activated via the Plotter format used during exposure.
Plotter Format
first form   

Future Figure: Plotter Format - first form

Note: Only the changes which are relevant to the new CreoScitex Class Screen are described below.

Class Screen

[toggle field; by default No]

Toggle this field to Yes to activate CreoScitex Class Screen.
Note: The User Dot option is not available in such a case

Dot Type

[toggle field; by default Composed]

Toggle this field to Geometric or FULLTone. For an explanation of these options, see the Geometric Dot and FULLTone sections above.

Geometric is available at all times (not depending whether Class Screen is set to Yes or to No).

FULLTone is available only if Class Screen is set to Yes. The angle and mesh parameters are then inactive.

If you toggled the field to Geometric or Composed, press <F6> (Next) twice to access the third Plotter Format form (see Setting Screening Parameters Below).

If you toggled the field to FULLTone, press <F6> (Next) twice to access the FULLTone Parameters form.

Future Figure: FULLTone Parameters form

Type of Fulltone [toggle field; by default Normal]

Toggle this field to the desired type of FULLTone screening.

Very Fine
produces the minimal distance between the centers of the laser dots. In the highlight areas, this option produces the smallest laser dots.

Fine   
produces dots which are larger than the ones produced by Very Fine.

Normal
produces a screen in which only some of the dots are enlarged. These are larger than the ones produced by Fine.

Coarse
produces a screen in which only some of the dots are enlarged. Unlike in Normal, the enlarged dots are scattered randomly.

Very Coarse
produces dots which are enlarged in the highlight and shadow areas (more dots than in Normal).

The following table shows combinations of FULLTone types with imagesetter resolutions which result in various printing qualities.

Note: The areas enclosed by the dashed lines indicate the recommended combinations; the black dots indicate the default settings.

Top Quality

When using 120 l/mm or 140 l/mm, productivity is low and film linearization is less problematic.

When using 60 l/mm, 80 l/mm, or 100 l/mm, productivity is high and film linearization is more problematic.

Set of Separations
Hl/Sh Dot Control
Minimum Dot Space [default is 1]
Maximum Dot Space [default is 3]

Set of Separations

[toggle field; by default Normal 1-4]

Toggle this field to the desired group of four (4) separations: 1-4 (CMYK), or 5-8, 9-12, 13-16 for additional colors.

Hl/Sh Dot Control

[the default value updates automatically according to Type of Fulltone;
for Normal - the default value is 1]

This field defines the number of dots in a given area. This helps minimize dot loss in the highlight areas during the plate making process.

Toggle to a value in the range 0-9. The higher the value, less and larger dots appear, and the wider the tone range that is affected. For example: 9 affects the 0-30% and 70-100% ranges. A large value produces rough results in the highlight and shadow areas.

Minimum Dot Space [default is 1]

Enter the value (in the range 1-8) that indicates the minimum distance between the centers of the dots.

Maximum Dot Space [default is 3]

Enter the value (in the range 2-9) that indicates the maximum distance between the centers of the dots.

A higher value enlarges dot size and helps minimize dot loss in the highlight areas during the plate making process. It produces rough results in the highlight and shadow areas.

Setting Screening Parameters

Overview
D Ratio G Ratio Dupli P Noise
Cell Size
Display final values [toggle field; by default No]

Overview

As in the previous software versions, screening parameters are set in the third Plotter Format form.

To access this form, press <F6> (Next) in the first and second Plotter Format forms. Note: Only if dot type (in the first Plotter Format form) is not FULLTone.

This third Plotter Format form changes according to the status of the Class Screen field (Yes/No) in the first Plotter Format form.

If Class Screen is set to No, the form appears as follows:

Plotter Format
third form   

Plotter Format - third form (for regular screening - Class Screen: No)

If Class Screen is set to Yes, the form appears as follows:

Plotter Format
third form

Future Figure:Plotter Format - third form (for Class Screen: Yes)

D Ratio G Ratio Dupli P Noise

Both form (shown above) indicate the parameters used for the relevant type of screening.

The conventional dot types (i.e., Round, Diamond, Square, Composite and Gravure) and the Geometric dot use D Ratio and P Noise.

G Ratio is used only by the Gravure dot type, and is inactive for all other dot types.

Cell Size

This field is not available if Class Screen is set to Yes.

Cell Connection [toggle field; by default No]

In previous software versions, if you exposed two (2) touching pages (Gap:0), a seam appeared between the pages.
Toggle this field to Yes to coordinate the dots between the neighboring pages so that no such seam is visible.

The following figure shows the difference in dot arrangement for both options.

Display final values [toggle field; by default No]

In previous software versions, a new Plotter format showed all the system defaults.

In this software version, the form is displayed empty and the prompts: Leave fields empty for SYSTEM default values. The system defaults are used during exposure unless you type different values in this form.

Toggle this field to Yes to display the system defaults in the form. You may then modify them, if desired.