In typography, letter-spacing, usually called tracking by typographers, refers to a consistent degree of increase (or sometimes decrease) of space between letters to affect density in a line or block of text.
Letter-spacing should not be confused with kerning. Letter-spacing refers to the overall spacing of a word or block of text affecting its overall density and texture. Kerning is a spacing adjustment of specific pairs of adjacent characters that, because of the relationship of their respective shapes, would appear to be too far apart if spaced normally. A classic example is a capital V next to a capital A in a seriffed typeface.
In its original meaning with metal type, a kern meant having a letter stick out beyond the metal slug it was attached to, or cutting off part of the body of the slug to allow (other similarly-trimmed) letters to overlap. So a kern in that sense could only bring letters closer together (negative spacing), though of course it was possible to add space between letters. Digital kerning can go in either direction. Tracking can similarly go in either direction, though with metal type one could only adjust groups of letters further apart (positive spacing).
Letter-spacing adjustments are frequently used in news design. The speed with which pages must be built on deadline does not usually leave time to rewrite paragraphs that end in split words or that create orphans or widows. Letter-spacing is increased or decreased by modest (usually unnoticeable) amounts to fix these unattractive situations.
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Word processing and desktop publishing programs for personal computers such as—Microsoft Word, WordPerfect, QuarkXPress, Adobe InDesign, Adobe FrameMaker, Adobe Illustrator, and Adobe Photoshop—use differing, non-standardized methods of adjusting subtracting letter-spacing. What is common to most systems is that the default letter-spacing is zero, using the character widths and kerning information built into the font itself. Although digital type sets tighter on average than metal type, this results from design decisions in the fonts and the more ready availability of kerning, rather than any design choice inherent in the technology.
In the days of machine-implemented lead typesetting, such as Linotype machines and the Monotype System, letter-spacing had to be uniform. In modern digital page-layout software, high-end applications all use relative measurements proportional to the size of the type. QuarkXPress uses units of 1/200 of an em, and the competing Adobe InDesign uses 1/1000 of an em. Thus, in QuarkXPress a tracking setting of 3 opens text noticeably, while in InDesign a tracking setting of 3 is barely noticeable.
The amount of letter-spacing in text affects legibility. Tight letter-spacing, especially in small text sizes, can diminish legibility. The addition of minimal letter-spacing can often increase the legibility and readability. Adding whitespace around the characters allows the individual characters to emerge and be recognized more quickly. Adding too much space, however, may isolate individual letters and make it harder for the reader to perceive whole words and phrases, which reduces readability.
Wide letter-spacing, beyond relaxed book composition, can look affected and earned the opprobrium of Frederic Goudy: "Men who would letterspace blackletter would shag sheep." When quoted, "shag" is often bowdlerised as "steal". Goudy's pronouncement inspired the title of Stop Stealing Sheep, an introduction to typography that Spiekermann co-authored.
In the days of hot metal typesetting, letter-spacing required adding horizontal space between letters of words set in metal type, in increments of a minimum of ½ point. Some publishers and typesetters avoided letter-spacing because it was costly in materials and labor. Letter-spacing required by-hand insertion of copper (½ pt.), brass (1 pt.), and printer's "lead" (2 pt.) spaces between individual pieces of type or between matrices. Despite the cost, letter-spacing was used in print advertising and book publishing. It was also used for very short phrases set in capital letters or small caps, to avoid the phrases appearing too black compared to the rest of the page.
Letter-spacing with fixed spaces
Letter-spacing may also refer to the insertion of fixed spaces, as was commonly done in hand-set metal type to achieve letter-spacing. This is a more mechanical method which relies less upon spacing and kerning tables resident in each typeface and accessed and used when letterspacing is applied universally. Fixed spaces include a hair space, thin space, wordspace, en-space, and em-space. An en-space is equal to half the current point size, and an em-space is the same width as the current point size.
Changing the kerning perception
Example on webpages: with CSS1, a standard of 1996, the letter-spacing property (illustrated) offer some control for lost or enhance "kerning perception" — kerning can be simulated with non-uniform spacing between letters. Only with the standard CSS3, scheduled for 2014, font-kerning property arrives with a complete control of kerning. In the meantime the web-designers used the workaround of letter-spacing, mainly to enhance spaced-texts of titles and banners.
- Kashida – analog in Arab-Persian scripts
- Sentence spacing
- Word spacing
- Emphasis in typography
- Comment by Erik Spiekermann (15 October 2005) in Wardle de Sousa, Tiffany (2 July 2005). "Famous Quotes from Type Designers". Typophile.com.
- Spiekermann, Erik; Ginger, E. M. (2002). Stop Stealing Sheep & find out how type works. Adobe Press. ISBN 0-201-70339-4.
- "Effects of intraword and interword spacing on eye movements during reading: Exploring the optimal use of space in a line of text", Timothy J. Slattery, Keith Rayner. August 2013, Volume 75, Issue 6, pp 1275-1292. DOI:10.3758/s13414-013-0463-8.
- "The Rhetoric of Typography: Effects on Reading Time, Reading Comprehension, and Perceptions of Ethos", Eva Brumberger. Technical Communication, Volume 51, Number 1, February 2004 , pp. 13-24.
- Bringhurst, Robert. The Elements of Typographic Style. Hartley & Marks: 1992. ISBN 0-88179-033-8.
- Kane, John. A type primer. Prentice Hall: 2002. ISBN 0-13-099071-X.
- Lupton, Ellen. Thinking with Type: A Critical Guide for Designers, Writers, Editors, & Students. Princeton Architectural Press: 2007. ISBN 978-1-56898-448-3).
- Spiekermann, Erik. Stop Stealing Sheep & Find out how type works. Adobe Press: 2002. ISBN 0-201-70339-4.
- Owen Williams, Testing David. Nakai Theatre Home Grown Festival 2008, Whitehorse, Yukon, Canada, (2008)
- A logo with tight tracking Notice the letters almost touch each other, especially the “r” and “a”
- A logo with loose tracking Notice the large amount of white space between letters. An entire extra letter could fit in between each letter.