IARIGAI Dubrovnik – Cavtat 2003, Croatia – Advances in printing science and technology: proceedings of the 30 th International iarigai Research Conference; UDK 655:004.91 > (063); 004.91:655 > (063); ISBN 953-96276-6-4 (tvrdi uvez); ISBN 953-96276-7-2 (meki uvez), Acta Graphica Publishers
New screening elements in multi-colour printing for special purposes
Jana Žiljak, Vesna Vančina, Darko Agić, Ivana Žiljak, Klaudio Pap
Faculty of Graphic Arts, University of Zagreb
This investigation determines new procedures of screening applied to multi-colour reproduction. Total individualisation of the image is obtained by introducing the new different screening system for each separation. This process is extended to the microstructure of the individual screening shapes, which was not described until now. Understanding of such procedures is closely linked to security printing, and therefore details are poor and not accessible. Solving of such problems involves team-work in various fields of research: design, prepress, materials in graphic processes, mathematical definition of screen systems and shapes, as well as protection methods for valuables. Proposed methods are performed by PostScript programming of output devices, optical measurements and experimental digital printing, using special, as well as conventional inks.
The first presentation on specially designed screen patterns #1 (Iarigai 1999) with new applications of screen elements emphasized the topic of security printing and document application. Stohastic selection of screen patterns was suggested as well as stohastic attribution of lpi and angle for each pixel. The second article (#2) (Iarigai 2001) exposed four-colored application with individualized screening. It offered program-solutions as a combination of stohastic selection of screen parameters with a fixed screening element. While the first and the second report applied pixel graphic, and deconstructed image using a stohastic selection of lpi and a screen element type, this article discusses screening of vector graphics for printing with new screening patterns.
This article provides solutions for programming and application of new screening elements requested by digital printing techniques. It offers an original code for PostScript programming. Our applications fall under the area of complex integration of pixel and vector graphics: design for jumbo posters, documents and securities, as well as textile design. These applications do not involve only an image but also a structure of graphic interpretation creating the image. Portions of a graphic solution have been generated by PostScript algorithms.
Surface objects of vector graphics are usually created as 100% spot colors. Designers emphasize use of spot colors hoping that each section of such a solution will result in print as a separate color. However, majority of their spot ideas result in four-colored CMYK screens.
Screening is necessary in case of designing of gradations and in
majority of cases a standard AM or FM screening is applied. Since
dotted image interpretation is considered as boring we have to minimize
a screening element - "it is better when it is hidden".
Tonal gradations in vector graphics should be screened and not printed
with full tone. It would cause problems with color register and trapping.
If a continued tone is dealt with a screen, a screening element should
change its shape, whatever its size. It means that if a screen element
is a crucifix it should be deformed in continuity depending on planned
bolding within a defined microstructure. An example is presented of
a continued transformation of a screen element propeller r14 as a
print-out of liniature two screening elements per inch compared when
the object is interpreted with continued changes (Figure 1), and when
the object is bolded uniformly by 70% (Figure 2) and 15 % (Figure
3). Each example is associated with the original PostScript code (program
1, 2, and 3).
The next step in application is the use of two or more colors with various patterns of screening elements. Each color requests a separate procedure. Low lineatures will create a special impression. Such a three-colored solution has been applied to the Croatian currency Kuna and improved this year with a new edition. One color reacts under ultraviolet light and another is visible in the infra-red range of the spectrum. At present we are planning solutions for each specialized application with a spot vector screening but the screening will be used only once.
This article presents seven unpublished images of screening elements and the reader may modify shapes of screening elements using the original code. These screening elements may be also used in vector and pixel graphic for printing. They can also be used for graphic solutions resulting from the PostScript program itself as presented on our Web pages #3 .
Microstructure of specialized graphic solution can be also created with copying tiny vector elements of an image. Such an file is huge so the question is whether we have a computer that can follow up within a reasonable timeframe how a designer develops an idea. On the other hand, programmed shape of a screening element does not burden computer’s memory and speed. The screening is carried out through an act of display or a print-out. Shapes of these tiny elements are not stored in the memory. There are no Bezier points that overflow the vector graphics. There is only an algorithm on the manner of processing, showing how a drawing has been created for a display i.e. for printing. Preference is for programmable graphics that has not been recorded as vectors or pixels. In the same document a designer may use numerous screening elements, planned or visualized on the monitor or a printer. Programmable graphics may create both pixel and vector graphics. As noted earlier programmable graphics has been generated during display. This article contains PostScript algorithms with maximum reduction, simplified for screening vector graphics with new screening elements. Deliberately we have created a very clean algorithm without a PostScript indirect adressing in order to encourage further research by other graphic artists especially younger ones. More detailed contemplation of the algorithm structure should lead to the creation of a large library of screen patterns and enrich a tendency towards personalization in the printing industry.
Programmable graphics is generated graphics, generated design, created by algorithms, mathematical procedures and parameter tricks. Although this article does not cross into the area of fractals let us mention that programmable fractals present the most interesting area of developing personal approach to design and digital press. The application of fractal principles will enrich the microstructure of a screening cell. It will result in new proposals for development of FM screening especially in the application of printing with ten different colors.
A three-dimensional, two-dimensional pattern and an active screen may be depicted and named freely. All proposed screens have been shown as bolded continually (zero to 1, loop from 0 to 250, step 0.004). Example (b) shows an application with the same screen or in a combination with another one. Screen names are: /r2, /r3, /r4, /r5, /r12, /r14 and /r16.
/r2 Dropping Eiffel: filling a screen up
changes a shape from the imitation of a letter Y,a drop, houses and
Designers still do not realize that even internal screening structure
calls for special even perso-nalized solutions. The use of low liniatures
of good visibility could bring sophistication into design. A question
is how to create interesting screen structures that are not usually
found around us. This article encourages designers to use new ideas
in screening their graphic designs.
At present a printing product results from a team effort, specialization and quick adaptation to advanced technologies. In the imminent future, designers’ projects will become more complex, have more contents thus demanding original solutions that use new materials and colors and diverse technological procedures. Optimal approach to productivity will be embraced by printing companies and designers prone to flexibility and adaptation to possibilities available to the printing industry at a certain environment. A graphic solution may be elaborated in various manners with minor differences. It is necessary to study all new proposals resulting from digitalization and Internet, to review them and build them into procedures for creating a graphic product. Screening an image, a graphic pattern and colored surface is a special trait of the printing industry. Methodology for display and visual presentation of a screening solution varies for each technology and it is completely different for Web, print, video and other aspects of multimedia. This article discusses new screening elements for print only that refer to personalization, digital printing, original visual solutions and their special application in designing documents. For these areas we have used printing with original screening elements thus opening up new opportunities with the creation of databases of new screenining elements and novel application in printing. This development is aimed towards a stohastic definition of screening types. The article offers original PostScript solutions with a sole purpose of creating interest with graphic artists and designers and providing incentives for their application in solutions for graphic products. We have tried to study the most detailed interpretation of screening printing and clarify all doubts so that the screening methodology could be used efficiently in a novel manner in the printing industry.