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Welcome to Peterborough Printers

Offset Printing

Offset printing is a widely used printing technique where the inked image is transferred (or "offset") from a plate to a rubber blanket, then to the printing surface. When used in combination with the lithographic process, which is based on the repulsion of oil and water, the offset technique employs a flat (planographic) image carrier on which the image to be printed obtains ink from ink rollers, while the non-printing area attracts a film of water, keeping the non-printing areas ink-free.

Currently, most books and newspapers are printed using the technique of offset lithography. Other common techniques include:

  • flexography used for packaging, labels, newspapers.
  • hot wax dye transfer
  • inkjet used typically to print a small number of books or packaging, and also to print a variety of materials from high quality papers simulate offset printing, to floor tiles; Inkjet is also used to apply mailing addresses to direct mail pieces.
  • laser printing mainly used in offices and for transactional printing (bills, bank documents). Laser printing is commonly used by direct mail companies to create variable data letters or coupons, for example.
  • pad printing popular for its unique ability to print on complex 3-dimensional surfaces.
  • relief print, (mainly used for catalogues).
  • rotogravure mainly used for magazines and packaging.
  • screen-printing from T-shirts to floor tiles.

 




Digital printing

Digital printing accounts for approximately 9% of the 45 trillion pages printed annually (2005 figure) around the world.[7]

Printing at home or in an office or engineering environment is subdivided into:

  • small format (up to ledger size paper sheets), as used in business offices and libraries
  • wide format (up to 3' or 914mm wide rolls of paper), as used in drafting and design establishments.

Some of the more common printing technologies are:

  • blueprint—and related chemical technologies.
  • daisy wheel—where pre-formed characters are applied individually.
  • dot-matrix—which produces arbitrary patterns of dots with an array of printing studs.
  • line printing—where pre-formed characters are applied to the paper by lines.
  • heat transfer—like early fax machines or modern receipt printers that apply heat to special paper, which turns black to form the printed image.
  • inkjet—including bubble-jet—where ink is sprayed onto the paper to create the desired image.
  • electrophotography—where toner is attracted to a charged image and then developed.
  • laser—a type of xerography where the charged image is written pixel by pixel by a laser.
  • solid ink printer—where cubes of ink are melted to make ink or liquid toner.

Vendors typically stress the total cost to operate the equipment, involving complex calculations that include all cost factors involved in the operation as well as the capital equipment costs, amortization, etc. For the most part, toner systems beat inkjet in the long run, whereas inkjets are less expensive in the initial purchase price.

Professional digital printing (using toner) primarily uses an electrical charge to transfer toner or liquid ink to the substrate it is printed on. Digital print quality has steadily improved from early color and black & white copiers to sophisticated colour digital presses like the Xerox iGen3, the Kodak Nexpress, the HP Indigo Digital Press series and the InfoPrint 5000. The iGen3 and Nexpress use toner particles and the Indigo uses liquid ink. The InfoPrint 5000 is a full-color, continuous forms inkjet drop-on-demand printing system. All handle variable data and rival offset in quality. Digital offset presses are also called direct imaging presses, although these presses can receive computer files and automatically turn them into print-ready plates, they cannot insert variable data.

Small press and fanzines generally use digital printing. Prior to the introduction of cheap photocopying the use of machines such as the spirit duplicator, hectograph, and mimeograph was common.

Color printing or Colour printing is the reproduction of an image or text in color (as opposed to simpler black and white or monochrome printing). Any natural scene or color photograph can be optically and physiologically dissected into three Primary Colors, red, green and blue, roughly equal amounts of which give rise to the perception of white, and different proportions of which give rise to the visual sensations of all other colors. The additive combination of any two primary colors in roughly equal proportion gives rise to the perception of a Secondary Color. For example, red and green yields yellow, red and blue yields magenta (a purple hue), and green and blue yield cyan (a turquoise hue). Only yellow is counter-intuitive. Yellow, cyan and magenta are merely the "basic" secondary colors: unequal mixtures of the primaries give rise to perception of many other colors all of which may be considered "tertiary."


Color separation process

The process of color separation starts by separating the original artwork into red, green, and blue components (for example by a digital scanner). Before digital imaging was developed, the traditional method of doing this was to photograph the image three times, using a filter for each color. However this is achieved, the desired result is three grayscale images, which represent the red, green, and blue (RGB) components of the original image:

The next step is to invert each of these separations. When a negative image of the red component is produced, the resulting image represents the cyan component of the image. Likewise, negatives are produced of the green and blue components to produce magenta and yellow separations, respectively. This is done because cyan, magenta, and yellow are subtractive primaries which each represent two of the three additive primaries (RGB) after one additive primary has been subtracted from white light.

Cyan, magenta, and yellow are the three basic colors used for color reproduction. When these three colors are variously used in printing the result should be a reasonable reproduction of the original, but in practice this is not the case. Due to limitations in the inks, the darker colors are dirty and muddied. To resolve this, a black separation is also created, which improves the shadow and contrast of the image. Numerous techniques exist to derive this black separation from the original image; these include grey component replacement, under color removal, and under color addition. This printing technique is referred to as CMYK (the "K" being short for "key." In this case, the key color is black).

Today's digital printing methods do not have the restriction of a single color space that traditional CMYK processes do. Many presses can print from files that were ripped with images using either RGB or CMYK modes. The color reproduction abilities of a particular color space can vary; the process of obtaining accurate colors within a color model is called color matching.

 

 

 


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