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Реферат «Prepress» по Английскому языку (Солодкина Е. В.)

Type and typographic imaging

Printing is the reproduction in quantity of words and pictures on page or document. Prepress is the first category of operations to accomplish the reproductions by printing, which is followed by press and postpress. Prepress is the series of operations involved in the preparation and assembly of all copy elements ready for printing on a printing press or digital printer.

Type Fundamentals

Typefaces are usually available in 6 to 72 point, with a complete font in each size. Capital letters are called uppercase and small letters, lower case. In lower case letters, the upper stroke is called ascender, and the downward stroke is known as descender.

Type Families

Some types have many variations, and these various styles are said to be in the same family. Examples of these variations in a type style are: light face, medium, bold, extra bold, expanded and condensed, with italic versions of each in most cases.

Printers’ Measurements

The point and the pica are two units of measure universally used in printing in most English-speaking countries. Their use is primarily in typesetting. Type size is measured in points. Line length measure is in picas and points. The point measures 0,376 mm or approximately 1/72 of an inch. Points are always used to specify the size of type. The pica is used for linear measurements of type. There are 12 points to 1 pica, and approximately 6 picas to 1 inch. The em is also important in typesetting although not a part of the point system. It is the square of the type size and is used for measuring the quantity of type.

Digital typesetting

Since the early 1980’s printing and publishing technology has been evolving digital methods of production. The bit becomes the building block of digital imaging . Scanners analyze images spot by spot to record the absence or presence of data. Most digital imaging devices use a laser. In the printing world, pictures are reproduce on printing presses as patterns of halftone dots.

An important factor concerns the reproduction of photographs and the relationship between spots per inch and halftone dots, or line screen. To create a halftone dot, that is, a specific level of gray as perceived by the human eyes, a matrix of about 10x10 of the printout unit’s spots is used.

Rasterization and imagesetters

The monotype lasercomp in 1978 and the Linotype Linotronic in 1980 used lasers to output grids or raster images of type on film for printing. Because they could produce images as well as type, they were called imagesetters rather then typesetters.

Digital type

All output devices today are raster based. This means that they create type and images as patterns of spots and dots on paper, film, plate and other substrates.

Personal Computers

Usually consisting of a keyboard, a video screen and a floppy disk, personal computers, also called workstations, have become the Model Ts of the electronics word. Easy-to-change software programs allow each unit to perform word processing, accounting and other functions for business or personal use.

Telecommunications

Information stored in most electronic text systems may be communicated over telephone lines. Modems convert signals from these systems into telephone signals and then re-convert them at the other end.

Interfacing The linking of different devices is called interfacing. It may be accomplished by reading a recorder medium, accepting telecommunications, or simply connecting the units by cable.

Mnemonic Mnemonic means memory oriented. For example you can remember the colors of the spectrum with the name ROY G BIV for red, orange, yellow, green, blue, indigo, violet. Many typesetting commands are mnemonic in nature.

WYSIWYG

This acronym for What You See Is What You Get refers to the images seen on the screen of a monitor. High-resolution monitors are over 72 dpi. Measured diagonally, a 19” monitor has an image of about 11”x14”. The goal has been to make the screen image look as close to the final printed image as possible.

Most video displays are now flat panel screens using LEDs or plasma technology. CRTs are being slowly phased out.

Copy and art preparations

Just as digital imaging has changed the mechanics of typesetting, copy and art preparations have been affected similarly. At one time, manuscripts were created on typewriters which then needed to be converted to type prior to typesetting and reproduction.

Imaging for graphic art

Imaging is the most important step in the hierarchy of prepress operations. Since 1850, photography has been the principal imaging system for photomechanical platemaking.

Principles of Light and Color

Knowledge of the principles of light and color is critical to proper use of all visual processes including photography, printing and digital systems. The visible light spectrum varies in color from violet to blue, blue-green, green, yellow, orange and red. Color is the combination of the physical sensations of light and the psychological interpretation of it.

COLOR REPRODUCTION

Color reproduction is based on the theory of three-color vision. It consists of color separation, color correction and color proofing, and all the operations involved in carrying out these functions.

COLOR SEPARATION

The process of color separation is analogous to seeing by the eye. The original photo or artwork is photographed using white light and three filters, each corresponding in color and light transmission to one of the additive primaries (RGB).

COLOR CORRECTION

Color corrections to compensate for spectral errors in inks and exposure errors in photography are made manually by dot etching, photographically by masking, and electronically through scanning and image processing software.

COLOR PROOFING The main purposes of proofing are to see (1) if all the image elements are represent, if they fit and are in the right color, and (2) how the job will look when it is printed. (1) is done on computer monitors and are called soft proofs; (2) is done on proofing systems and are referred to as hard proofs. Visual analysis indicates if and where corrections are necessary.

DIGITAL PREPRESS

The conventional prepress operations of typographic imaging, copy preparation, photography and film assembly involve intricate manual operations which are very time consuming and cost intensive, and require highly skilled, expensive professionals. These manual operations have been the most serious bottlenecks to production, which is why most new developments in the industry have been targeted at these prepress areas.

DIGITAL IMAGE PROCESSING

The first graphic arts processes to be computerized were two of the most important steps in the hierarchy of prepress operations. They were typesetting and color separation by electronic scanning.

TYPESETTING Digital typesetting started as photomechanical typesetting in 1949 on a converted line casting machine. It was followed by electromechanical typesetting in 1954 using optical projection of type characters on rotating font discs.

SCANNERS The scanner is one of the most important elements in digital and color electronic publishing technology. The first commercial electronic scanner was introduced in 1950. It was a drum-type scanner that recorded images as light intensities.

COLOR ELECTRONIC PREPRESS SYSTEMS

Early developments in digital imaging were color electronic prepress systems (CEPS). These Were high-end systems introduced in 1979 and used in the decade of the 1980s that attempted to perform all the steps from the original copy to the press plate in one system of integrated units.

DESKTOP PUBLISHING

Device-independent digital imaging systems began to enter the graphic arts in the 1980s. They use personal computers and off-the-shelf hardware and software that can perform many of the prepress functions of color reproduction. These systems were popularly called desktop publishing or desktop prepress.

WORKSTATIONS

The computer hardware and operating system on which the software runs is called the platform, and the combination of the hardware/operating system, monitor, input devise and peripherals is called the workstation.

PLATEMAKING Platemaking, or, more correctly, making the image carrier (as some processes like gravure and screen printing use other imaging surfaces), used to be the culminating step in the prepress process where the results of all prepress operations combine to fit the needs of the different printing processes. Platemaking is now more logically part of the press or printing operation.

LITHOGRAPHIC PLATES

Lithography is a planographic process using thin metal plates (except for the new litho stones still used by artists) with the image and non-image areas essentially on the same plane. Lithography is based on the principle that oil and water do not mix. A lithographic plate is precoated with a light-sensitive or thermal-sensitive imageable coating and the separation between the image and non-image areas is maintained chemically.

FLEXOGRAPHIC PLATES

Flexography is a relief process and its plates are similar to letterpress plates except they are softer and resilient. The introduction of special photo-polymer plates extended the use of flexography to many other printing markets such as newspapers, flexible films, pressure sensitive and other labels, and corrugated boxes and packaging.

GRAVURE PLATE AND CYLINDERMAKING

Gravure is an intaglio process in which the image areas are cells in a thin copper shell plated on a steel cylinder, and a steel doctor blade keeps the non-printed areas clean during printing. Gravure differs from other processes in that it is capable of printing varying amounts and densities of ink to produce images that simulate continuous-tone images.

SCREEN PRINTING

Versatility is the principal advantage of screen printing. Any surface can be printed (wood, glass, metal, plastic, fabric, cork, etc.) in any shape or design, any thickness and any size. In advertising, screen printing is used for banners, posters, billboards, counter displays, menu covers, etc. The screen is a porous material and the printed image is produced by blocking holes or pores of the screen representing the non-printed areas.

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