Printer Languages
January 23, 2008
Historically, the printer industry has always adopted one or two vendors’ own printer languages for each different printer technology, and these have become the industry standards that others emulate. The reason is simple: the best way to sell printers is to make them compatible with the software used on computers, and the safest way to ensure compatibility is to fall into line with the best-selling models you’re competing against. If you were to develop your own language, you’d raise your costs and run the risk that software companies wouldn’t consider it worthwhile to “drive” your printers.
In practice, there are two main sets of industry standards that affect the mainstream printer buyer. One of them — PCL — was developed by Hewlett-Packard (HP); the other, PostScript, comes from Adobe Systems. These days, all printers that handle both PCL and PostScript are able to switch between them automatically, depending on the job they sense coming in from a PC. Rarely will users know how their print requests are being handled.
There’s also a low-end alternative — often called Windows GDI printing — that is actually not so much a printer language as a completely different approach to printing: it involves relying on the host computer to do more of the processing work that’s ordinarily carried out in the printer itself. GDI printing reduces the cost of printer hardware but can place a burden on your PC. GDI is typically found in low-end printers. There is an equivalent to GDI on a Macintosh. Together, these approaches are called host-based printing, and they are basically about treating the printer like a computer monitor, so you pretty much get on the printed page what you see on the screen. This works fine for everyday printing, but it may prove unsatisfactory for more demanding work.
PCL 5e & PCL 6
Hewlett-Packard sells more printers than anyone else and has set the leading industry standards. As a result, almost all the printers other than the least expensive offer PCL-compatible printing in one form or another. PCL comes in a number of versions — PCL 4 and 5 are history for newer printers. The lowest level you’ll encounter on new machines is generally PCL 5e.
We won’t spend time explaining the differences between PCL 4 and PCL 5, as these are pretty academic nowadays. But the difference between PCL 5 and PCL 5e is worth noting. The important thing to keep in mind is that printers whose hardware is capable of working at 600dpi will default to 300dpi in regular PCL 5 mode. To print at 600dpi with PCL, you need PCL 5e (or better). PCL 5e doesn’t stop at 600dpi — the growing number of 1,200dpi lasers on the market are able to work at their highest resolution with PCL 5e.
The current version of PCL, dating back to 1996, is called PCL 6. The advantages over PCL 5e come down to a series of important, but highly technical, points; the bottom line is that you’ll get faster and better-quality graphics printing (you won’t notice it as much on text).
PostScript
As indicated above, the main alternative to the various PCL languages comes from Adobe Systems, and it’s called PostScript. Unlike Hewlett-Packard, Adobe does not make or market printer hardware. It’s a software company that licenses its product to printer manufacturers that build it into their machines.
The main differences between PCL 6 and PostScript concern not so much the images they can create (although there is a bit of that) but the way in which they work and their compatibility with different types of output devices. PostScript is especially suitable for applications involving desktop publishing and graphics. It is also the dominant printer language for the Mac OS environment, where PCL does not work.
Not all PostScript is the genuine Adobe article, however. Many printer vendors use PostScript-compatible software from third parties. There was a time when this was viewed as a riskier proposition than selecting the original Adobe version. Today, this is no longer the case — while some PostScript emulations may be more blue chip than others, the cloned varieties are now deemed pretty respectable. Some companies trumpet that they have genuine Adobe PostScript, but we have heard of few problems with the nonstandard versions.
A few years ago, many printer vendors treated PostScript as a premium, extra-cost option. But PostScript prices have fallen considerably in response to the growth of PCL 5e and PCL 6, and fewer vendors continue to charge extra for it. In fact, you’ll find PostScript offered as standard on many low-end models that would be competitive even without it.
PostScript 3
In the past, the majority of PostScript printers used PostScript Level 2 (or a third-party emulation thereof). In 1997, however, Adobe rolled out PostScript 3 (the word “Level” has been dropped from the nomenclature), and all current models are compatible with it.
Most of the enhancements that came in PostScript 3 are detailed and complex — while they may appeal to graphics professionals, they are not likely to excite the mass of printer buyers with limited interest in the intricacies of what takes place under the hood. That said, two benefits that might catch the printer buyer’s imagination are (1) increased performance (that is, shorter job times) and (2) the enabling of various print-over-the-Internet technologies. Keep in mind that not all PostScript 3 models are compatible with all of the new features.
PCL & PostScript: the differences
With PCL, your computer software sends commands to the printer one at a time — print this, print that, print this, and so forth. With PostScript, by contrast, your computer software sends the “big picture” to the printer all in one go; the software in the printer then interprets the data and prints the page accordingly. In jargon terms, PCL is known as a “command language,” while PostScript is known as a “page-description language.”
One consequence of this is that the actual speed you get from a PostScript printer will be significantly determined not just by the mechanical speed of its engine but also by the power of its built-in processor and the extent of its memory. That’s because, with PostScript, a lot more of the computing work goes on inside the printer rather than inside the computer. That doesn’t mean that the processing power of the printer is of no importance with PCL; it’s a matter of degree.
PostScript’s most clear-cut advantage over PCL is its ability to work across different computer platforms (that is, it is not a Windows-centric printer language) and to drive all manner of output devices at any resolution. In particular, it is used to drive the ultra-high-resolution imaging equipment found in professional graphics and production printing environments. If you work with files that will ultimately be handled by an outside service provider with such equipment, you’ll want to work in PostScript and you’ll really need to have PostScript printers in-house for proofing and other purposes.
That’s why users of graphics and publishing software such as Quark XPress and Adobe InDesign and Illustrator tend to be very PostScript-oriented. It doesn’t mean that PCL machines can’t print documents produced on these programs — they can. But they simply aren’t as suitable, and there may be certain graphic images that they will have problems printing.
TIFF and PDF printing
A number of printers are specially configured to cater to those who need to print scanned images, especially TIFF images. While any TIFF — or EPS or GIFF — image can be printed by ordinary printers, this can clog performance and prevent a machine from operating at close to its rated engine speed.
An imaging printer is one that can accept, decompress, and output raw bitmapped images — such as TIFF images — without first converting them into PCL or PostScript. Cutting out the printer language enables image printing at or near rated engine speed. A few machines in this guide offer direct TIFF imaging as a standard feature.
Another type of file that is growing in importance is PDF — Portable Document Format. A PDF file can be read in its original layout by anyone, regardless of the computer operating system (either Windows or Mac), without needing the application program that was used to create it. PDF, which is the creation of Adobe, is especially handy for sharing files over the Internet because of its compact file size — even when the files contain text and complex graphic images. As with TIFF, printers that can output PDF files directly, without translation into a printer language, offer a speed advantage over those that can’t.
Of course, you can print most PDF files by opening them in Adobe Acrobat Reader, a free program, and just printing them. (The computer will then convert the file, which can be slow with large files.) Direct PDF printing means that you can simply drag a file icon onto a printer or click on the Print command icon and start printing.
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