Typography

Typography is the art and techniques of arranging type, type design, and modifying type glyphs (see fonts). Type glyphs are created and modified using a variety of illustration techniques.

Typesetting

The is the term used for the actual task of setting type (typeset) which controls font, text sizes, color, page breaks, and all of the other typography elements.

In contrast most eBook text formats are free-flowing as opposed to typeset, meaning the rendering program is free to choose font, base text sizes, and color. Simple formatting commands are normally supported, such as Bold, Underline, Center, Page Break, etc.

Measurements

Typesetting has its own measuring system. At one time fonts were fixed, made out of metal, and only the maker of the font need worry about most measurements but now that they are defined digitally there is an increasing need to understand how they are measured. Metal fonts included the space between the lines as well, since the printer expected the metal typefaces to just be placed on the press, but sometimes this is not in the digital measurement.

At the highest level a font is defined by its point size. A point is 1/72 of an inch and is often used to determine how many lines will fit in 1 inch. It is abbreviated as pt. Since fonts characters are different heights and widths the letter m (called em) is used as the standard character size. To measure really small items such as the distance between letters a rule was defined to allow the font maker to specify an arbitrary number to make these measurements. This is defined in the font set as the UPM, Units per em. This is often set to 1,000 but can be any value. Once this is determined everything can be measured in UPM units.

Another measure is called the "pica". A pica in typography equals 12 points or 1/6 of an inch. It is abbreviated as pc. A pica is a very old measure used to define metal type height. The term "pica" also became used as the measure for a typewriter as the number of standard lines in an inch (6). The typewriter pica is a fixed width font with 10 characters per inch horizontally. Another common size on typewriters is "elite" which was narrower with 12 characters per inch.

Typography elements

The arrangement of type involves the selection of typefaces (fonts), point size, line length, leading (line spacing), letter-spacing (tracking), justification, and kerning.

Leading

Leading can have a surprisingly dramatic effect in the legibility of a page of text. Increased leading is often used to set off paragraphs. However too much leading can actually detract from the reading experience for some users. This is one area where user preference in a software package can have a positive effect.

Fonts generally are measured from the baseline (the bottom edge of standard fonts). The Leading is divided into 3 measures from the baseline. These are the ascent (height of a capital letter), the descent (the drop of characters that go below the line), and the line gap (the remaining space in the leading). Unfortunately there are three different ways these are measured with the windows method including the gap in the other two values. Font display tools try and reconcile these different methods. For more information see Vertical-metrics tutorial.

Kerning

Kerning is the process of adjusting letter spacing in a proportional font between pairs of letters. In a well-kerned font set, the two-dimensional blank spaces between each pair of letters all have similar area. While tracking specifies the distance between the rectangular box that constrains a font character, kerning can go inside the box of an adjacent character to overlap the two characters. This permits a typographer to control the visual area between two glyphs. For example the box outline approach in this wiki causes an AV combination to visually appear farther apart than HB.

Examples of letter pairs that need kerning treatment are AV, AY, PA, and AT. These letter pairs often look awkward together, and need to either be moved closer together, or further apart manually. Professional typesetting systems and fonts allow fine-grained adjustments for such letter pairs. Popular word processors either lack support for kerning tables or disable kerning by default.

Ligatures

Some letter combinations have been determined to look better is they are especially spaced. For example fl can be shown using a ligature fl or fi can be shown as fi. These are called Stylistic ligatures. Ligatures can also be combination character such as OE shown as Œ. See special characters for more examples. This use is not typographic but rather an alternate spelling using a special letter to represent the correct phoneme. Accent marks such as umlauts were developed to avoid this use of these combination letters.

Justification

Justification refers to alignment of the edge of a block of text. Left justification (also known as ragged right) is used by most Latin based languages (left to right letter flow). Some middle-east languages need right justification due to their right to left letter flow. Often left justified is assumed and thus not specified. When a user says the text was justified they may mean that it is fully justified, meaning both left and right edges of the block of text line up.

Full justification is best implemented using a combination of tracking and word spacing. Some simple eBook software uses only word spacing with can result in a poor looking page of text with visual rivers running through the page. Even with tracking there can be a river effect. This can be minimized by adding the extra spacing from the left on one line and then from the right on the next line. Full justification can be disconcerting on short lines due to the fact that the line may have only a few words an spacing must be exaggerated to achieve full justification. Good support for hyphenation can help by adding an additional partial word to the line.

Non-justified text is often used in titles and poetry. For example a title may be centered on a page. Poetry may use centered lines or some form of specialized indenting.

Vertical justification is also important to the presentation of a page. When leading varies and paragraph spacing varies a full page of text may not exactly line up near the bottom margin. If this happens good typography would be accomplished by justifying the vertical space by adding a small bit of leading.

Tracking

Tracking adjusts the letter spacing within words. It is often misnamed Kerning which is a special subset of tracking. Fonts are generally designed with minimum tracking but in some instances the document would look better with additional space between the letters. Justification is best done using a combination of tracking and word spacing but even unjustified text or left justified text can benefit visually from tracking adjustment. Even adding a single point (or pixel) between letters can make a document easier to read. From time to time there can even be negative tracking used to squeeze the letters together.

Hyphenation

Hyphenation of a word at the end of a line can improve or detract from typography. Done properly the use of hyphenation can help to balance the line length to avoid extreme differences in the length of adjacent lines. Over use of hyphenation on multiple successive lines can really detract from the looks of the page and the reading experience.

The advent of computers has been detrimental to the use of hyphenation when it is accomplished with an algorithm. Many times it results in a division at the wrong place in the word and even when done correctly a later reformatting change can result in the hyphenation continuing on a word in the middle of a line. Correct implementation will use the concept of a soft hyphen so that it will only appear when needed. Manually placed soft hyphens can also guide the software as to the correct hyphenation points for a word. The development of hyphenation dictionaries can help combat these problems.

Text Typography

In traditional typography, text is composed to create a readable, coherent, and visually satisfying whole that works invisibly, without the awareness of the reader. Even distribution with a minimum of distractions and anomalies are aimed at producing clarity and transparency. In subtle ways this attention to detail can enhance the reading experience.

Unfortunately most eBook software or eBook Readers pay very little attention to typography. Hopefully this will improve in the future. Some electronic formats such as PostScript and PDF do permit typography techniques to be employed. The idea of ligature is supported by many electronic font sets but publishers seldom take advantage of this capability.

Display Typography

Display typography is an important element in graphic design, where there is less concern for readability and more potential for using type in an artistic manner. Type is combined with negative space, graphic elements and pictures, forming relationships and dialog between words and images.

These techniques are often used in advertising, posters, book covers, some logos, etc.

Figure Typography

Generally speaking figure fonts (numbers) are included with the letter fonts in a font set. However, there are two main typography variations in figures. These are called lined figures and non-lined figures, also known as text figures or old style numbers. Text figures differ from lined figures in that some of the figures extend below the line similar to lower case letters. The figure on the right show text figures taken from Hoefler Text. The referenced article explains the history of this form of typography. A particular font set will generally include only one choice for figures, generally lined, where all of the figures set on the lines used for capital letters. Some font sets do include both font types.

To use text figures you need a different set of font glyphs but since they are really the same unicode character there is no easy way to reference which set you want even when they are both included in the same fonts. Unicode provides for a private area that can be used to reference these glyphs. For example, Adobe's "Pro" fonts use codepoints U+F643 to U+F64C to encode text figures.

Fleurons

Fleurons are decorative glyphs that are used in books to provide separation between sections (end marks) or as decoration around text. Two Unicode fleurons are provided in the dingbats font set. These are:

• U+2766 (❦) (HTML: ❦)
• rotated floral heart bullet, U+2767 (❧) (HTML: ❧).

Another fleuron is found in the miscellaneous symbols block:

• reversed rotated floral heart bullet, U+2619 (☙) (HTML: ☙).

For more information

• http://en.wikipedia.org/wiki/Typography
• http://www.microsoft.com/typography/
• CSS provides the ability to specify typographic elements.
• LaTeX provides full control of typography.
• Typography - complete guide.
• Fleurons article in wikpedia.
• Fontspace is a source of free fonts including fleurons and other decorative glyphs.
• 18th Century Ligatures and Fonts - describes some historical typography
• http://en.wikipedia.org/wiki/Blackletter describes Gothic script