The Printing process

Printing Process?

The printer is one of the most important peripherals of your GIS because it allows you to print out data on paper. The choice of printers is huge, ranging from modest black and white ink-jet printers, to heavy-duty colour laser or high resolution imagesetters capable of reproducing negatives for use in high-quality printing. We are going to study here the printers and printing technologies that exist on the market, so that you could determine at the end of this lesson the best printing method, according to your quality and quantity objectives.

PrePress

Prepress refers to the preparation of digital files for printing. It comes after the design and page layout stage and concerns the fundamentals of digital imaging, font and file management, and desktop publishing.

PrePress File Format

Before submitting a digital file for printing, confirm what file formats your printer can accept. Some printers prefer application files but may not be able to accept files from all applications or all versions. In lieu of original application files, most printers can accept (and some prefer) PostScript or PDF files.

• PDF files: PDF stands for Portable Document Format. As the name implies, it is a data format that can be used to describe documents. In prepress, PDF is used more and more as a format to exchange data between applications and to proof material before going to press. You can for example, convert your map to PDF in order to see a rough proof on screen.
• PostScript files: Postscript is the page description language that includes the instructions for an imagesetter to replicate pages on your computer to film, printing plates or even laser printers. These instructions can include fonts, printer’s marks, text, graphics and halftones.

Learn more (optionally) about PrePress on : http://desktoppub.about.com/ (accessed the 26/04/2004)

The Printer Characteristics

Resolution

The resolution of a printer is synonym of the printing quality. This resolution is measured in dots per inch (dpi). Take the example of a printer having a resolution of: 1400 X 720 dpi (dots by inch). The first value indicates the number of dots present on a horizontal line having a length of one inch. So, the horizontal line of one inch of length will consist of 1400 dots. The second value indicates the number of dots present on a vertical line having a length of one inch. So, the vertical line of one inch of length will consist of 720 dots. You will have understood that the higher the resolution of the printer is high, better the quality of printing is.

A good printing resolution will be higher than 600 X 600 dpi.

Printing Speed

The printing speed indicates the speed in which the printer prints a page. This speed is expressed in page per minute (ppm). Take the example of a ink-jet printer having the following characteristics:

• Speed of printing in monochrome mode: 6 ppm
• Speed of printing in colour mode: 2 ppm
• Speed of printing in mode photo: 1 ppm

The first value means that the printer can print text with a speed of six pages per minute. The second value means that it can print in colour, a mixture of texts and graphs or drawings with a speed of two pages per minute. The third value means that the printer can print a colour photo with a speed of one page per minute.

Ink-Jet Printers and Plotters

Ink-jet printers can be black-and-white or with colours. They allow a good sharpness and precision work (in black and white or in colour). Some models allow printing of photography quality images. The Ink-jet technology is used for standard printers size (dinA3 or dinA4 paper), but also for plotters (dinA0 paper).

Some Ink-Jet Printers advantages and inconveniences are:

• Advantages: They offer low-cost quality colour outputs and do not create a lot of noise.
• Inconveniences: The print quality of ink-jet printers is lower than that of laser printers, and they tend to be very slow. However, they provide a low-cost solution for printing colour maps.

Laser Printers

Laser printers have a very good precision, are fast, and print in black-and-white and in colour. However, laser printers are more expensive than ink-jet printers.

Some Laser Printers advantages and inconveniences are:

• Advantages: Laser printers offer a very good printing quality, are fast and can print out 25 pages per minute.
• Inconveniences: Laser printers are generally in black-and-white because colour lasers cost too much.

Laser printers are the workhorses of desktop publishing, and they are getting faster and cheaper all the time.