Printers

Printers Category

From old to modern, printer terms demystified

True Black

  • Black produced by a separate black ink rather than the “composite black” produced from a mixture of cyan, magenta and yellow. See also Composite Black.

Toner

  • A special type of ink used by copy machines and laser printers. Toner consists of a dry, powdery substance that is electrically charged so that it adheres to a drum, plate, or piece of paper charged with the opposite polarity.

Thermal Transfer

  • A printer technology that uses heat to transfer coloured dye onto paper.

Thermo Autochrome

  • A print technology which has emerged in digital camera companion printers and which is claimed to produce photographic-quality output on a par with the more well-known dye-sublimation technique.

Raster Image

  • An image defined as a set of dots/pixels in a column-and-row format. Rasterisation is the process of determining values for the dots/pixels in a rendered image. See also Bitmap.

Process Colours

  • The four primary ink colours (CMYK) used in colour printing.

Printer Dot

  • The individual pixel in a halftone image. The size of a printer dot is variable, ranging from zero (all white) to the size of the halftone screen (all black).

PostScript

  • A page description language developed by Adobe. Generally used by laser printers, PostScript is becoming increasingly common in high-end inkjets too.

Pigment Inks

  • While conventional inks are essentially oil-based dyes, pigment inks consist of tiny chunks of solid pigment suspended in a liquid solution. According to their proponents, pigment inks offer richer, deeper colours and have less tendency to run, bleed or feather.

Piezo-Electric

  • The property of certain crystals that causes them to oscillate when subjected to electrical pressure (voltage).

PDL

  • Page Description Language: a language for describing the layout and contents of a printed page used with laser printers. The best-known PDLs are Adobe PostScript and Hewlett-Packard PCL (Printer Control Language). Both PostScript and modern versions of PCL are object-oriented, describing a page in terms of geometrical objects such as lines, arcs, and circles.

PCL

  • Printer Control Language: a protocol designed by Hewlett-Packard to allow PCs to communicate with its laser printers. PCL has become a de facto standard for laser and ink jet printers and is supported by virtually all printer manufacturers. “HP compatible” or “LaserJet compatible” means that a printer supports the PCL command set.

Parallel Port

  • An I/O channel for a parallel device, like a printer, which sends and receives data eight bits at a time over 8 separate wires. Maximum throughput is around 500 Kbit/s. Increasingly, other devices such as removable storage drives, scanners etc. share the printer parallel port using a “pass through” mechanism.

LPT1

  • The first parallel or printer port on a PC.

LED Printer

  • An electrophotographic printer that uses a matrix of LEDs as its light source. The LED mechanism is much simpler than its laser printer counterpart. A stationary array of LEDs is used instead of numerous moving parts, and the LEDs are selectively beamed onto the drum.

LCD Printer

  • Similar to a laser printer. Instead of using a laser to create an image on the drum, however, it shines a light through a liquid crystal panel. Individual pixels in the panel either let the light pass or block the light, thereby creating a dot image on the drum.

Laser Printer

  • A type of printer that utilises a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work.

Inkjet

  • A printer technology where ink is splashed onto the printer paper to form an image or character.

Halftone

  • A method of expressing colour gradation in continuous-tone images. The image is resolved into dots, with dark colour being expressed by a large number of dots and diluted colour is by a smaller number of dots. The dot patterns used are called dithers. Halftone dots are not the same as printer dots.

GDI

  • Graphical Device Interface: a component of Windows that permits applications to draw on screens, printers, and other output devices. A GDI-compliant printer will print exactly what is displayed on a Windows screen without having to transpose it into a printer language. Since all the processing happens on the PC, the printer doesn’t require since image processing circuitry, reducing its price.

Feathering

  • A term used when describing printed text quality. Feathering occurs when deposited ink follows the contours of the paper. Depending on the viscosity of the ink, the rougher the grain of the paper the more pronounced the feathering will be.

Dye-Sublimation

  • A specialist print technology used for demanding graphic arts and photographic applications that require continuous tone output.

Dot Matrix

  • A type of printer, also known as serial dot matrix, that uses one or two columns of dot hammers to form images out of dots. The more dot hammers used, the higher the resolution of the printed image.

Dithering

  • The process of intentionally mixing colours of adjacent pixels. Dithering is usually needed for 8-bit colour, and sometimes for 16-bit. It allows a limited colour set to approximate a broader range, by mixing groups of varying-colour pixels in a semi-random pattern. Without dithering, colour gradients like sky or sunset tend to show “banding” artefacts.

Diffuse Dither

  • A method for printing continuous-tone images on laser printers in which the greyscale information is represented by randomly located printer dots. Diffuse dithers do not photocopy well because of the small, random, dot location in the image.

Contone

  • A technique used by colour printing technologies which is a compromise between increased halftone cell size (giving more shades per halftone cell) and increased resolution (giving less invisible halftone cells).

Composite Black

  • The creation of black from cyan, magenta and yellow inks. Mixing inks is not a perfect operation, and composite black is often muddy. This is why the CMYK model is used in professional printing. See also True Black.

CMY

  • Cheaper, single cartridge inkjets use the Cyan Magenta Yellow model. Black, referred to as composite black, is made up from the three colours. Dye-sublimation uses these three colours on the print ribbon.

Centronics Interface

  • This 36-pin connection was designed by Centronics Corp. and has become the preferred way to attach most printers to a PC parallel data port.

Bubble Jet

  • Canon’s trade name for its thermal drop on demand ink jet printer technology. The ink is heated, which produces a bubble that expands and ejects the ink out of the nozzle. As the bubble cools, the vacuum created draws fresh ink back into the nozzle.

Bleeding

  • A print distortion where adjacent colours run and merge into one another, sometimes caused by excess ink or paper which is too absorbent.

Banding

  • Bands of discrete colour or tone that appear when an inkjet can’t reproduce a smooth graduation from one colour to another. Instead there are noticeable jumps between one value and the next.

WPS

  • Windows Print System: the scheme supported by Windows 95 in which the operating system spools data from an application in Enhanced Metafile Format (EMF), instead of raw printer data. The spooler interprets the data in the background and then passes appropriate commands to the printer. Like with GDI, all the processing is done on the PC.

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