Printers

A wide range of printers are available, providing different features according to price. Before choosing a printer you should try it out, preferably with the kind of paper you intend to use.

Your preferred printer will be a matter of personal taste. However, you should check for:-

Most modern printers are laser-class or ink-jet devices, although there are numerous variations and special features. For example, duplex printing lets you print on both sides of the paper in a single ‘pass’ without having to turn the paper over. The device prints on one side of the paper, sucks the paper back in and then prints on the opposite side of the sheet.

Unlike some manufacturers, Apple usually supplies printer driver software for their older printers with the Mac OS, although they no longer make printers. Unfortunately, with third-party products there’s always a risk that a newer version of the system won’t work with your existing driver and that the printer manufacturer will fail to provide an update.

Ink Types

There are basically two kinds of ink: pigments and dyes. Laser printers employ pigment-based inks, which are dry in their original form and are then melted onto the paper by the printer. Such inks don’t permeate the surface but remain on top, resulting in a high density of colour. More recent ink-jet printers employ special resin-based inks that dry very quickly, also giving good colours. The results of printing with pigment-based inks should last between 80 and 100 years.

Low-cost ink-jet printers use dye-based inks, which are usually water-based. These take a time to dry and therefore soak into the paper, reducing the colour density, whilst the ink can also ‘bleed’ across the surface. The output of a printer that uses dye-based ink may last only 30 years.

Cartridges and Heads

Good colour printing requires at least three colours of ink. This is usually stored in one or more ink cartridges and fed to an appropriate number of print heads where it’s dispensed onto the paper.

The ideal printer has separate ink cartridge for each colour, allowing you to easily replace each colour of ink as it’s used. Unfortunately, some machines employ combination cartridges that contain some or all of the inks, forcing you to dispose of cartridges that contain perfectly good ink. Low-cost colour printers often have a single cartridge for all the colours, although you may be able to replace this by a larger black ink cartridge. Where separate cartridges are provided, the black cartridge is often the same size as the rest. And, since most text is in black, this always runs out first.

Printer Ink Colour Combinations

Ink consumption depends on the required colour density and on the amount of paper to be covered in ink. It also increases when higher-quality printing is needed. For example an Apple StyleWriter cartridge can print 500 pages in Best mode, but this increases to 2,000 pages in Faster mode.

Printing Quality

Resolution and Speed

The performance of a printer is set by its printing mechanism. In most instances a compromise is made between the printer’s resolution, usually measured in dots per inch (dpi), and the speed of printing, given in pages per minute (ppm).

Printers can operate at a resolution of 300, 360, 400, 600, 720, 800, 1000, 1200, 1440, 2400, 2880, 4800 or even 5760 dpi. In some instances the vertical and horizontal resolution is different, as in 600 × 2400 dpi. Such devices usually provide a higher vertical resolution, ensuring accurate reproduction of the ‘serifs’ on small text characters.

Colours

The maximum colour density or blackness of printing is set by a printer’s ink colours and the nature of the ink. Low-cost colour printers typically use three to six ink colours, such as:-

Inks Colours Abbreviation
3Cyan, Magenta, YellowCMY
4Cyan, Magenta, Yellow, Black/KeyCMYK
6Cyan, Magenta, Yellow, Black/Key, Light Cyan, Light Magenta CMYKcm

A 6-colour printer creates more shades, giving more accurate hues and smoother gradients, usually by means of photo cyan and photo magenta inks. Similarly, a 7-colour printer often uses these colours with the addition of light black ink, whilst an 8-colour device may add light grey and medium grey inks, all of which are very effective in photographic printing.

Half-toning

Printers sometimes employ half-toning to reproduce those shades or colours that can’t normally be created by the printer’s own ink or inks. For example, a printer that only has black ink can’t normally generate a greyscale image, but with half-toning it can give a fairly good illusion. The process works by dividing the paper into a grid of small areas, only some of which receive ink. Typically, each area is a square consisting of 25 pixels, 5 pixels high and 5 pixels wide. The density of these squares is specified in lines per inch (lpi), where each ‘line’ is actually a line of such squares.

A printer that uses half-toning has an lpi rating, which is related to the printer’s resolution by the following equation:-

Square height (pixels) = resolution (dpi) ÷ number of lines per inch (lpi)

Hence a typical 300 dpi printer operates at 60 lines per inch (lpi) with 5 pixel high squares.

Printer Families

The following types of printer are can be encountered:-

  Laser-class

This type of printer is based on photocopier technology, in which toner ink, made up of a ‘dust’ of toner particles, is attracted to chosen parts of a page of paper by an electrostatic charge. This is then sealed onto the paper by passing the sheet through heated rollers. The heavy-duty mechanism in this type of machine is ideal for use in a busy office. Despite the name, some ‘laser’ printers use light-emitting diodes (LEDs) instead of a laser, and are sometimes known as a LED printer.

The resolution of such devices is usually in the range of 600 × 600, 1200 × 1200 or 600 × 2400 dpi, although higher resolutions are possible. Most machines support PostScript, which means that the printer must have internal memory to store all of the PostScript fonts used for each printed document. Such memory is usually in the form of random access memory (RAM), with typical sizes of 4, 8, 16, 24, 64 and 128 MB. For modern requirements a printer needs at least 16 MB of RAM, although 32 MB or more is preferable if you intend to print high-resolution graphics.

Older colour printers are effectively constructed of three or four ‘cascaded’ monochrome laser mechanisms, each using a different colour of toner ink, and requiring up to four passes to reproduce every colour. This makes such devices very slow, typically giving 3 to 4 pages per minute (PPM). Fortunately, most modern machines use a four-colour toner cartridge with single-pass operation, offering an improved performance of between 12 and 24 PPM.

Ink-jet

Also known as a bubble-jet printer, this type of machine works by squirting a small amount of ink onto the paper. The earliest technique employs a thermal print head, which is usually combined with the ink cartridge, resulting in a rather expensive cartridge. The head heats up a small quantity of ink in a chamber just behind a nozzle in the ink head, causing the ink to ‘spit’ onto the paper. This incredibly simple idea provides a very cheap form of printing that’s ideal for domestic use.

Other models have a piezoelectric print head built-in or within a separate module, which makes the cartridges cheaper. High frequency (HF) sound vibrations project the ink forwards, making the head less prone to clogging than the thermal type.

The ink in these printers tends to bleed across the paper, especially when using photocopier paper, whilst colour pictures, requiring more ink, can make the paper wrinkle. Using glossy paper prevents these problems, but is expensive.

Solid ink

This technology, used in printers from Tektronix, employs ink in the form of a wax crayon that’s melted and fed onto the paper in a similar way to an ink-jet printer. Devices of this type can produce a glossy and impressive result, making them ideal for reproducing photographic material. Older devices can be slow, perhaps only giving one page per minute, although modern printers of this type are fast, since full-colour printing is often provided in a single pass.

Dye-sublimation

This kind of printer uses rolls of differently coloured dye-coated sheets, each of which are applied in turn. The paper is fed up to four times through the machine by means of grippers, requiring accurate registration on each pass. Unfortunately, a margin is normally required to accommodate the grippers, meaning that you can’t print right up to the edge of the paper.

Continuous tones are created by the dyes melting into each other. Ideally, photographic paper should be used, although text is often blurred. The process is expensive, since up to four sheets of dye roll are needed, even to print part of a page.

Thermal Wax

Similar to dye sublimation (see above) but using wax-coated rolls, again giving continuous tones.

  Dot-matrix

A very low-cost and noisy form of printing, involving a set of solenoid-operated pins that push the appropriate part of an ink-coated ribbon against the paper. Although highly reliable, the results aren’t usually aesthetically pleasing.

Printer Connections

Most printers have a modern form of wired connection, such as USB, FireWire or Ethernet.

The following information may help you when connecting various interfaces.

Universal Serial Port (USB)

This plug-and-play port is very convenient, since it’s available on all modern computers. Unless you need a very fast circuit, or need direct wiring into a network, this is the preferred form of connection.

FireWire

Another plug-and-play interface, fitted to all modern Macs and many other machines. It provides a fast connection and is only usually necessary if you have a exceptionally high-quality printer.

Ethernet

Most computers and many printers have this fast network connection, often in 10Base-T form, operating at 10 Mbit/s, or as 100Base-T, running at 100 Mbit/s. Not all devices support both speeds, although 100Base-T devices usually accept 10Base-T data. Even if your computer doesn’t have an Ethernet port you can usually fit an Ethernet card or other suitable hardware.

Wi-Fi

This wireless network system, as defined in the IEEE 802.11b and IEEE 802.11g standards and also known as AirPort in Apple terminology, can be employed to connect several computers and printers.

Bluetooth

This wireless interface lets you connect suitable printers to your computer, assuming the machine has built-in Bluetooth hardware or is fitted with a Bluetooth adaptor. The latter often consists of a small device that plugs into a spare USB port.

Apple ‘Classic’ Serial Port

This connection, provided on a mini-DIN socket, appears on ‘classic’ Mac OS computers. Most machines have separate Printer and Modem ports, although some models have a single socket, accommodating only one device at a time.

If the Printer port isn’t used for LocalTalk (see below), you can connect a compatible printer using a suitable printer cable, which has identical plugs at both ends. You can also use the Modem port for a printer, although this often causes confusion.

RS-232/RS-422 Serial Port

This interface, used in professional systems and on some PC printers, is similar to an Apple serial port, but with extra circuits. Suitable printers often contain DIP switches, sometimes hidden inside, that must be configured to suit the connection.

Apple LocalTalk

LocalTalk is Apple’s proprietary and obsolete networking system for ‘classic’ Mac OS machines, allowing printers and computers to communicate by means of AppleTalk software. Each device on a network must have an external LocalTalk box, which is plugged into a LocalTalk-compatible printer or into the Printer or Modem port on a Mac OS computer. However, if you only have one LocalTalk printer and one computer you can connect the two together via a ‘classic’ serial printer cable.

SCSI

This fast parallel interface is provided on all ‘classic’ Mac OS computers, but requires the installation of a suitable PCI card in newer machines and involves cumbersome wiring and multiway connectors. Some older types of LaserWriter have this kind of connection, which is convenient if you have a SCSI port available and don’t need to use the printer over a network.

Centronics Parallel Port

Another fast parallel interface, as found on many PCs and PC-related printers. An LPR bidirectional parallel port, as intended for a LPR printer, is similar but comes with additional features.

Infrared (IR)

A infrared printer can be used in the vicinity of older PowerBooks and other IR-equipped devices, including Palm organisers, as well as hand-held computers and mobile phones.

At the time of writing, some IR printers, notably from Hewlett-Packard, can’t be used in Mac OS X.

Dot-matrix Printers

In computer terms a dot-matrix printer is closely related to the dinosaur. However, such a device can still perform a useful function in limited applications or where nothing else is available. The following may be of use to those whose interests are moving in the direction of computer archaeology!

Using a Dot-matrix Printer

The main advantages of dot-matrix printers are low running costs, reasonable printing speed and acceptable reliability, even under adverse conditions, making them ideal for printing envelopes or churning out large numbers of address labels. They can also print invoices onto carbon-backed paper, generating several copies of each document in a single pass.

Sadly, such machines are noisy, give poor print quality, except in near letter quality (NLQ) models, and often use a ribbon cartridge that’s difficult or impossible to find (although you can load new ink into an old ribbon).

Whatever printer you use, you’ll need a suitable printer driver and, in some cases, other special software. Depending on the model, you may require an interface cable, card or adaptor box to connect your printer to the computer.

Essentially, dot-matrix printers come in two types:-

Apple-compatible Printers

An older printer, as designed for a ‘classic’ Mac OS machine, such as the ImageWriter or ImageWriter LQ, can be connected to the Printer port or Modem port of the computer. Such a printer can’t be connected to a modern USB port without using a USB to Apple serial adaptor that’s compatible with your model of printer.

Most Apple dot-matrix printers can be persuaded to work with other computers that have a standard serial port, since they can be switched to run at speeds of 300, 1200 or 9600 bit/s, although they default to 9600 bit/s with eight data bits and one stop bit. A form of handshaking known as DTR is normally used, although X-ON or X-OFF codes can also be employed. These and other options are usually set by DIP switches inside the printer.

Non-Apple Dot-matrix Printers

Only a desperate enthusiast should try to use this kind of printer with a Mac OS machine. Most non-Apple printers have a PC-compatible parallel port, also known as Centronics, usually wired via an Amphenol connector. To connect this to a modern computer you’ll need a USB to parallel adaptor or cable, whilst a ‘classic’ Mac OS machine requires a Apple serial to parallel converter box or cable. Fortunately some printers, particularly Epson models, can be fitted with an internal serial adaptor card, avoiding the need for an external adaptor.

The Apple serial to parallel adaptor or serial adaptor card may need to be configured to match the ‘classic’ serial interface, which can be a tricky task. Typically, such settings are concerned with data length, parity error selection and speed. Of the latter, 300, 600, 1200, 2400, 4800 and 9,600 bit/s are commonly used. The highest of these is usually quicker than the actual mechanism of a dot-matrix printer.

To actually use the printer you’ll need a special printer driver. Failing this, you could try Chuck’s Printer Driver, a special Classic Mac OS package that works with numerous printers.

Dot-matrix Operation

A dot-matrix printer employs a vertical column of solenoid-operated printing pins to push an inked ribbon against the paper. As printing progresses, this ribbon moves along to expose fresh ink. A standard dot-matrix printer usually has 9 pins, producing characters of 9 × 9 dots. In a typical near letter quality (NLQ) machine a total of 18 pins may be used, providing characters of 11 × 18 dots. In fact, a good NLQ printer can produce quite reasonable results.

By default, most non-Apple printers are initially in text mode with the NLQ mode of operation switched off. Most models can also be switched into graphics mode, which allows control of the pins to be directly handled by the computer. This is usually a slow process with unimpressive results.

Switching between these modes is achieved by sending special control codes and escape sequences to the printer. Many models use the Epson Standard Code for Printers (ESC/P) or IBM printer codes, whilst Apple printers use codes of their own. Although ESC/P and IBM use several common or similar codes there are also numerous differences that can cause confusion.

Most non-Apple printers store character shapes in the printer, rather than as fonts in a computer. In standard text mode, fixed-width or non-proportional characters are usually used, giving a specified number of characters per inch (cpi) of paper. Most devices normally work in pica pitch (10-pitch), giving 10 cpi, although slightly narrower characters can be produced by using elite pitch (12-pitch) at 12 cpi. And for really narrow text you can use condensed mode.

For bold characters, a printer can use one of two methods. In emphasised mode, each character is printed twice, the second impression being positioned slightly to the right of the first. However, in double-strike mode, the second impression is printed slightly lower than the first.

The following table shows typical modes used for text, indicating the maximum number of characters that can be accommodated in each line:-

StyleChars
10-pitch standard80
10-pitch double-width40
10-pitch condensed137
12-pitch standard96
12-pitch double-width48
12-pitch condensed137

The default style of 10-pitch results in a printout of 80 characters per line, corresponding to the number of characters in each line of a standard text file, as created on a PC.

Character Sets

Unfortunately, some dot-matrix printers don’t use the same codes to represent each character. In other words they use different character sets. This is a particularly thorny problem with old printers, since the characters are actually built into the device’s hardware. Ideally, the printer driver supplied with the printer should adjust the codes that it sends to the printer to correct this. But even this can’t usually persuade a printer to produce characters that aren’t contained within it, although in theory it might be possible to switch the printer briefly into graphics mode to create such characters.

In a typical non-Apple printer the codes from 32 to 127 are used for the standard character set, 128 to 159 are used for graphical symbols and 160 to 255 are employed for an alternative character set. In some printers the latter contains a further set of characters, similar to the standard characters but in a different style, commonly italic.

Reference

MacWorld magazine (UK), IDG Communications, 2004

©Ray White 2004.