Near letter-quality printing

Near letter-quality (NLQ) printing is a process where dot matrix printers produce high-quality text by using multiple passes to produce higher dot density.^[1] The tradeoff for the improved print quality is reduced printing speed. Software can also be used to produce this effect.^[2][3] The term was coined in the 1980s to distinguish NLQ printing from true letter-quality printing, as produced by a printer based on traditional typewriter technology such as a daisy wheel, or by a laser printer.^[4]

In 1985 The New York Times described the marketing of printers with the terms "near letter-quality, or N.L.Q." as "just a neat little bit of hype",^[2] but acknowledged that they "really show their stuff in the area of fonts, print enhancements and graphics".

Technology overview

Near letter-quality is a form of impact dot matrix printing. What The New York Times called "dot-matrix impact printing",^[2] was deemed almost good enough to be used in a business letter^[5]

Reviews in the later 1980s ranged from "good but not great"^[6] to "endowed with a simulated typewriter-like quality".

By using multiple passes of the carriage, and higher dot density, the printer could increase the effective resolution.^[4][7] For example, the Epson FX-86 could achieve a theoretical addressable dot-grid of 240 by 216 dots/inch using a print head with a vertical dot density of only 72 dots/inch, by making multiple passes of the print head for each line. For 240 by 144 dots/inch, the print head would make one pass, printing 240 by 72 dots/inch, then the printer would advance the paper by half of the vertical dot pitch (1/144 inch), then the print head would make a second pass. For 240 by 216 dots/inch, the print head would make three passes with smaller paper movement (1/3 vertical dot pitch, or 1/216 inch) between the passes. To cut hardware costs, some manufacturers merely used a double strike (doubly printing each line) to increase the printed text's boldness, resulting in bolder but still jagged text. In all cases, NLQ mode incurred a severe speed penalty.

Because of the slow speed of NLQ printing, all NLQ printers have at least one "draft mode", in which the same fonts are used, but with only one pass of the print head per line. This produces lower-resolution printing, but at higher speed.

Expensive NLQ printers had multiple fonts built-in, and some had a slot where a font cartridge could be inserted to add more fonts.^[2] Printer utility software could be used to print with multiple fonts on less-expensive printers.^[2] Not all of these utilities worked with all printers and applications, however.

References

1. "IBM Printing Draft Quality on OKI Microline Dot Matrix Printers".
2. Peter H. Lewis (December 17, 1985). "Getting the most out of a dox matrix printer". The New York Times.
3. "Printer Utilities: One need not spend a fortune to get fancy fonts, however. Many reasonably priced dot-matrix printers can be persuaded to perform like the more expensive models through the use of printer utility software."
4. Erik Sandberg-Diment (June 4, 1985). "Personal computers; Letter quality, almost". The New York Times. Letter-quality printers, which use a traditional typewriter technology such as that of a daisy wheel or some other print head having fixed characters on it for stamping characters onto paper, definitely produce the crispest and cleanest-looking copy, particularly when printing on rag bond paper.
5. Dot Matrix, InfoWorld Jul 28, 1986. 28 July 1986.
6. "reminded me that I was reading text printed by a printer rather than by a typewriter. Output from both draft and NLQ modes falls into the category of good but not great. In NLQ, the edges of the letters are slightly ragged." "Near letter quality: good but not great". PC Magazine. Ziff Davis. November 10, 1987. p. 286.
7. "... it is accomplished by shifting the print head ever so slightly after each character and then reprinting it. The double strike produced in this fashion yields a higher dot density."