Image and Data Visualisation: Fundamentals of Digital Typography

(Reference taken from: Steane, J. 2014, The Principles & Process of Interactive Design. London, Bloomsbury)

To understand and appreciate the application of typography, it is essential to first become familiar with the basic characteristics and features of letterforms. Through their understanding, you can diagnose issues with a particular typeface and communicate what characteristics you are looking for when discussing typeface selection with fellow designers.

Two important terms to begin with are ‘typeface’ and ‘font’. These common terms are not strictly interchangeable and have different meanings. A typeface is a set of one or more fonts that share a stylistic unity and form part of a type family. A font is a single character set of a particular typeface and size. Letters, numbers and other symbols that make up a character set are individually known as ‘glyphs’.

Measuring Type

Type size is traditionally measured in points (pt), with 72 points equivalent to an inch (2.54 cm). For screen-based design, type is increasingly measured in pixels (px) and in ’ems’. Although a point is a fixed measurement, two fonts can appear to be of different proportions when they share the same point size. This is due to differences in fonts’ relative ‘x’ heights and widths.

Type size is measured from the lowest descender of a font’s letterforms to just above the highest ascender, and a font’s x-height is measured from its baseline to the height of the lower-case x. Therefore, those fonts with short ascenders and descenders, or tall x-height, will appear relatively larger than others. Similarly, fonts with less height variation between its upper-case and lower-case letters will also appear larger.

The width of letterforms will also affect a font’s relative size. A font’s point size relates to its height only and not its width, so condensed fonts will visually appear smaller than those with broader widths. The width of a font is normally expressed in character per pica and this measurement is used to estimate how much text will fit into an allotted space.

An Anatomy of Type

Type Measuring


Old Style, Transitional and Modern Stresses


Kerning, Leading and Tracking


The Stress refers to the angle of the thin stroke in rounded letterforms. Historically, ‘old style’ serif typefaces, such as Caslon, have inclined or ‘oblique’ stresses whereas ‘modern’ serifs, such as Bodoni, have vertical. Typefaces of the ‘transitional’ period have semi-oblique stresses, for example, Baskerville.


A ligature is the joining of two or more characters to create a single glyph. Ligatures have their origins in ancient manuscripts and were designed to stop letter shapes colliding. he most prominent ligature is the joining of ‘f’ and ‘i’ to make ‘fi’.

Letter Spacing – Tracking and Kerning

Letter spacing is measured in ems. An em is a relative measurement and is traditionally based on the width of the widest capital letter of an alphabet, namely the letter ‘M’. General letter spacing is known as ‘tracking’ whereas individual spacing between two letters is called ‘kerning’. Note: an em is now commonly used to describe the relative height of letterforms too, where 1 em = the point size of the font.


The spacing between lines of type is known as ‘leading’. This historical term comes from the days of movable metal type when different thickness of lead were placed between lines of type to aid readability. Leading of lead is expressed in points, too. For example, 10/12pt is 10pt type on 12pt leading.

Styles and weights

Versatile typefaces come in a series of styles known as ‘weights’. For example, the Neue Helvetica typeface family show not only the standard regular, bold and italic, but also a whole range of different stroke weights.

In the past 25 years, we have also seen the growth of ‘super families’, which include Serif, Sans Serif and Slab Officina and Thesis. These super families are designed to work harmoniously together and give a visual consistency to a design across a variety of uses.


Roman inscriptions inspired serif typefaces. The term ‘serif’ describes the angular details at the ends of letter strokes. Old-style serifs date back to the fifteenth century and serifs today are associated with traditional book and newspaper publishing.

Sans Serif

Sans Serifs are ‘Grotesks’ came into prominence at the end of the eighteenth century, partly as an aesthetic reaction to the over ornamentation of serifs and, more practically, as a need for typefaces with greater legibility. Sans Serifs are commonly used for signage and information graphics, and work well on screen.

Slab Serif

Slab Serifs are characterized by thick block-like serifs. they first came into use at the beginning of the nineteenth authoritative nature. For this reason, heavy slab serifs are used sparingly as they are uncomfortable to read for more than a few lines of continuous reading.




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