Print about printers; color printers: worth the wait? (evaluation) Owen W. Linzmayer.
In Print About Printers this month we discuss three technologies used in the current generation of color printers: impact dot matrix, thermal transfer, and ink jet. We also examine two representative printers in the first two categories and one in the third.
Although color printers have been available for several years, only recently have falling prices brought them within reach of the average computer user (see Figure 1). Increased competition between printer manufacturers coupled with recent advances in technology have resulted in the introduction of a variety of low-cost printers capable of producing a rainbow of colors in addition to that old standby, black.
The demand for color printers has developed as the popularity of computers capable of generating and displaying color graphics has increased. Having grown accustomed to transferring word-processed text from screen to paper, users began to look for ways to capture their dazling color graphic displays on paper. The new breed of low-cost color printer combined with appropriate software now makes it possible for virtually anyone to join the color revolution.
Not everyone needs a color printer. For the vast majority of users, color printers represent an attractive luxury, hardly a necessity. If, however, you are a heavy user of computer art or business programs that produce charts in color, a color printer will be a welcome addition to your system.
Software is the key to taking advantage of the full spectrum of features offered by color printers. All word processors that allow you to embed control codes can print text in color. For example, "ESC r (1) Warning" is the control sequence that instructs the NEC Pinwriter P2C to print the word "Warning" in magenta (see Figure 2). Even the Macintosh, a monochrome computer, can print in color if it has the correct software driver. Software must recognize the ability of printers to produce colors before you can print in color.
Even though software packages like Broderbund's Dazzle Draw are beginning to support color printing, the relative scarcity of color photocopiers has kept color printers from catching on in the business world. A Lotus 1-2-3 pie chart can easily be reproduced in color using the Canon Ink-Jet printer, but because color printers are slow, it would take days to run off the several hundred copies of a report an executive might need to distribute to his sales force. This problem should diminish in importance as more affordable color photocopies become available.
All color printers, regardless of the printing method used, have several features in common. With the exception of the Cannon Ink-Jet printer, which accepts special ink cartridges, all of the printers mentioned here employ multi-color ribbons composed of red, yellow, blue, and in some cases, black strips. If you have ever wielded a crayon, you know that all the colors in the rainbow can be created by mixing the three primary colors (red, yellow, and blue). All of the color printers I evaluate here can create a minimum of seven colors (see Figure 3) by overstriking the primary ribbon colors in multiple passes of the printhead. With the appropriate software they can theoretically produce hundreds of different hues. In addition to the typically more expensive multi-color ribbons, most color printers accept standard black ribbons for those applications in which color is not needed.
Quite an Impression
Impact dot matrix printers are by far the most popular computer printers today. Therefore it should come as no surprise that the first color printers used this technology. Impact dot matrix printers form characters using precisely positioned dots; hence their name. The printhead is essentially a set of vertically arranged print wires (also called pins) that strike the inked ribbon and press against the paper when voltage is applied to them. This impact causes a dot to be printed on the paper. As the printhead moves across the paper, these tiny pins fire rapidly to form characters.
The Epson JX-80 is one of the most widely recognized color printers on the market, which can be attributed partially to Epson's excellent reputation and widespread influence in the printer industry. Listed at $699, the JX-80 offers a print speed of 160 draft characters per second (cps), a bevy of character modes, both tractor and friction feed mechanisms, and seven-color printing.
The JX-80 uses cloth ribbon cartridges (see Figure 4). Like the majority of impact dot matrix printers, the JX-80 produces colors by moving the multicolor ribbon up and down so that the desired color is in front of the printhead when the pins fire. That's all there is to it. When the program instructs the printer to use blue, the blue section of the ribbon moves into position. If a mixed color like green is required, the printer first prints yellow, and then overstrikes with blue. As a general rule, the light colors are printed first.
The major advantage of the Epson JX-80 is that it is one of the best supported color printers as far as commercial software is concerned. The tried and true impact dot matrix technology is well suited to printing on standard paper, which is not the case with thermal transfer printers, as we shall see. The JX-80 is also relatively fast, although it should be pointed out that the speed of all color printers is determined largely by the efficiency of the software driving them.
Drawbacks of the Epson JX-80 include inconsistent impact which results in a washed out quality that is most noticeable on graphic images with large areas of a single color (see sample). Disappointingly, the vibrant colors of a graphics screen lose a lot of their luster when put to paper simply because of the media involved. And finally, the cloth ribbons tend to smear and deteriorate in color quality after extended use.
The NEC Pinwriter P2C is a color version of NEC's immensely popular Pinwriter dot matrix printer. The claim to fame of the Pinwriter P2C is its 18-pin printhead, compared to the 9-wire head of the Epson JX-80. More pins mean superior print resolution and speed (180 draft cps). They also cost you more--the Pinwriter P2C retails for $999.
This NEC printer produces color in much the same was as the JX-80. Additional features include the color brown and a superior near-letter-quality text mode (see sample). The computer of choice for the Pinwriter P2C is the IBM PC, but it can be easily connected to any computer with a parallel interface. The Pinwriter P2C was designed primarily for correspondence, but does a superb job with graphics as well.
The Heat Is On
Thermal transfer printers arrived on the scene a little over a year ago and have yet to capture a significant market share. One problem is that the major contenders in the printer industry are slugging it out in a price war in which consumers are the real winners. Impact dot matrix printers bursting with features are selling for well under $300, and the inexpensive thermal transfer units with their special paper and ribbon requirements are having a difficult time gaining acceptance.
Thermal transfer printers are dot matrix printers, but differ considerably from impact dot matrix printers. Thermal transfer printers like the Apple Scribe and Okimate 20 do not strike the ribbon or paper to form characters. Instead, thermal transfer printheads contain discrete heating elements which gently contact the ribbon and melt its wax-base ink onto the paper. The technology provides extremely quiet operation, but the printers that use it are typically slower than comparably priced impact dot matrix machines. Not to be confused with obsolete, low quality thermal printers, which burn characters onto heat-sensitive paper, thermal transfer printers require special smooth-surface paper for best results.
The Apple Scribe and the Okimate 20 printers use similar, but incompatible, three-color wax-based ribbon cartridges. The ribbon itself is approximately 0.5" wide and consists of an 8" band of yellow, followed by an equal length of magenta and then cyna (see Figure 4). To produce the full range of colors, thermal transfer printers must pass through all three color bands for each line of printing. This accounts for reduced printing yield and speed when using color ribbons as compared to standard black. To determine what color is ready for printing, a photosensor on the printhead looks for a small marker located between the cyan and yellow bands on the ribbon.
Seven colors are available on the Scribe and the Okimate 20, yet the latter claims "over 100 sizzling colors." These colors are more accurately described as shades, produced by printing adjacent dots in different combinations of the standard colors (see below). The $299 Scribe is designed primarily for use with Apple IIc and IIe computers and employs a 24-element printhead to produce acceptable near-letter-quality text and double hi-res graphics. The Okimate 20 also uses a 24-element printhead and costs $268, but you must buy a separate Plug 'N Print interface (serial or parallel) for the IBM PC. Okidata also offers the $239 Okimate 10 for Atari and Commodore 64 owners (see sidebar).
While I am not very fond of the text quality of thermal transfer printers, they outperform everything in their price range when it comes to color graphics. Thanks to the wax-based ribbon, colors are consistent, and brilliant, and actually shine on the printed page. Screen dumps created with impact dot matrix printers can't hold a candle to the beautiful output of thermal transfer printers (see below).
Thermal transfer printers are not without their faults, however. First and foremost is the high cost of the special smooth stock paper and color ribbons which are exhausted after printing only 8-10 pages. Of equal importance is the fact that few software packages take advantage of the color capability of these printers. With its strong software developer ties, Apple is trying to encourage authors to write color-capable software for the Scribe. Okidata includes with each Plug 'N Print module a helpful utilities disk that allows you to do straight screen dumps and modify the picture by rotating it or by changing parameters such as background color and print size.
Jet Propelled Printer
Ink-jet printers are dot matrix printers of sorts, but instead of striking a ribbon against paper to produce characters, ink-jet printers spray fine droplets of ink. As shown in Figure 8, the printhead of the Canon Ink-Jet printer consists of four ink-jet nozzles (for yellow, magenta, cyan, and black). Each nozzle consists of a small glass tube with a transducer wrapped around the tip. When voltage is applied to the transducer, it squeezes the nozzle and an ink droplet is ejected from the orifice by the resulting pressure. Ink-jet printers that use this method are referred to as "drop-on-demand printers."
Instead of using cloth or wax-based ribbons, the Canon Ink-Jet printer accepts two ink cartridges, one tri-color and one black, which plug into the front of the unit. A complex series of pumps, filters, and reservoirs is used to draw the ink out of the sacks in these cartridges and prepare it for delivery to the ink nozzles (see Figure 6).
Both impact dot matrix and thermal transfer printers form text characters in one pass of their printheads. However, instead of having 9 or 24 print wires arranged vertically, the Canon Ink-Jet printer has four nozzles arranged horizontally, which means it must make seven passes of the printhead to form a 5x7 dot matrix character (see Figure 7). While this printhead arrangement is less than ideal for printing straight black text, it is well-suited to rapid printing of colors mixed on one line. The Canon Ink-Jet printer doesn't have to fuss with positioning the appropriate ribbon when it wants to print color, it simply applies voltage to the transducer around the nozzle of the desired color. This is the beauty of drop-on-demand printing.
If your primary use of a color printer is to produce lots of color charts and drawing, then the Canon Ink-Jet printer coupled with the appropriate software is a good bet. However, I was disappointed to find that the model I evaluated offers only draft quality text, and its character set does not have true descenders (see below). Obviously this printer will not do double duty for word processing.
I want to stress that there are other color printes available, and that the information in this column is not intended to cover all color printers on the market. Rather, I have discussed those printers which are most representative of the printing methods they employ. Other manufacturers that offer color printers include IDS, Axiom, Hermes, Dataproducts, Atari, Juki, and Facit.
Products: Epson JX-80 (computer printer)
NEC Pinwriter P2C (computer printer)
Apple Scribe (computer printer)
Okidata Okimate 20 (computer printer)
Canon A-1210 (computer printer)