Topography/Legibility

While legibility is usually defined as the assessment of the fine details of typeface design, and in an operational context this usually means the ability to recognise individual letters or words, typography in relation to documents, is defined as the presentation/ arrangement and layout of whole bodies of text. The two terms are often used interchangeably in the literature when reviewing aspects of style to improve readability.

The aim of any document is to communicate content to the reader as unambiguously as possible. To achieve that aim the content needs to be composed to create a readable, coherent, and visually satisfying whole that works, ideally without the awareness of the reader. The reader should be assisted in navigating around the information by optimal inter-letter, inter-word and particularly inter-line spacing, coupled with appropriate line length and position on the page, careful editorial “chunking” and choice of titles and reference links etc.

According to Rousseau⁴⁵, there are four steps of interaction between the viewer and the design of a document, for the design to effectively convey its meaning:

1. noticed
2. encoded [decoded]
3. comprehended
4. complied with by the viewer

Rousseau states that all four steps must be successfully completed to achieve successful communication. In relation to medical reports, step 1 that the document is ‘noticed’ is largely assumed through the act of sending it to a specific person. Step 2, that the information is compiled or ‘encoded’ is ultimately the responsibility of the author and to achieve step 2 the author will need to consider the individual elements of text and document design and how these elements interact to ensure a document’s legibility. Steps 3 and 4 are largely to do with the reader of the report, though arguably comprehension is a matter of the author ensuring the language and content used can be understood by the reader as much as it is the reader’s responsibility to concentrate while reading and assimilate the information.

There are many published papers and books on legibility analysing the various individual aspects of text topography:

• Typeface /Font. Typeface consists of all characters, in all sizes, of a particular design. Font is all the characters (upper and lowercase, figures, fractions, reference marks, etc.) of one size of one particular typeface. There are investigations into various aspects of character design related to different fonts including x-height (the height of the lower case “x” in a typeface) Figure A; ascenders (vertical strokes which rise above the body of a character or x-height), descenders (strokes which fall below the baseline of the x-height) Figure B; counter forms (the “negative spaces” inside a character) Figure C; serifs (or lack of (sans) serifs), and stroke weight (how thick or thin the lines are).
  Figure A
  
  Figure B
  
  Figure C
  
  • The legibility of seriffed fonts is of particular debate and there are many studies on this one area alone. Serifs are the small finishing strokes on the end of a character and one school of thought is that serifs are used to guide the horizontal “flow” of the eyes, with the lack of serifs said to contribute to a vertical stress, which is supposed to compete with the horizontal flow of reading46. Advocates of this theory say that serifs help in combining separate letters into word-wholes and letters with serifs are more easily differentiated by readers than letters without serifs^47-49. However others believe that this is not supported by research into eye movements which has established that eyes do not move along a line of text in one smooth sweep but in a series of quick jerks called saccadic movements^50-51. Other studies suggest that there is no difference between the legibility of serif and sans serif typefaces⁴⁶,⁵²,^53-54,⁵⁵.
  • Poulton⁵⁶ tested several fonts for legibility and found that x height was a significant factor in legibility and that fonts with the same x height (rather than point size) had relatively the same level of legibility.
  • A study conducted at the New England College of Optometry⁵⁷ found that horizontal letter compression had a greater effect on readability than vertical letter height.
  • Bernard et al⁵⁸ identified 5 font types that were perceived as being the most legible: Courier, Comic, Verdana, Georgia, and Times. However, examining legibility of some of these commonly used fonts both serif and sans serif (Century Schoolbook Courier, Georgia, Times New Roman, Arial, Comic Sans MS , Tahoma and Verdana) by means of reading efficiency, resulted in no significant difference between the fonts⁵⁹. However, there were significant differences in reading time. Generally, Times and Arial were read faster than Courier, Schoolbook, and Georgia. Fonts at the 12-point size were read faster than fonts at the 10-point size. In this study Verdana appeared to be the best overall font choice. Besides being the most preferred, it was read fairly quickly and was perceived as being legible.
  • Bernard et al⁵⁸ also noted that different fonts were perceived in different ways eg ornate fonts like Bradley and Corsiva were perceived as having a great deal of personality and elegance; Courier and Times were perceived as being the most business-like, whereas Comic was perceived as being the most fun and youthful.
  • Letter spacing relates to the amount of space used between letters which can be both positive and negative. Negative spacing is where space is removed between certain characters eg Yo, WA so that there is overlap between the letters. According to Bix⁶⁰ letter spacing is widely recognised to impact legibility, but there is little documentation with regard to specific requirements for legible messages.
• Leading or line spacing. Leading is the space between the baseline characters line to line. Eg.
  
  A small leading means that the ascenders and descenders, line to line are closer making it less legible. According to Bix⁶⁰ the optimal amount of leading for maximum legibility is dependent on the elements of both letter and message design eg bolder typefaces need more leading.
• Colour contrast. The majority of research findings are consistent in this area: dark text on a light background provides the best legibility^61-63. Bradley et al⁶³ also suggest that these combinations avoid difficulties associated with red/green colour blindness.
• ALL CAPS are generally not recommended in the literature being regarded as less legible⁶⁴ than sentence case.
• ‘Adequate’ or ‘ample’ white space is deemed an important feature of readability in several readability assessment tools such as The Suitability Assessment of Materials (SAM)⁶⁵, and the User Friendliness Tool (UFT) ¹² since it is promotes visual breaks and as noted by Valenstein², reduces clutter.

Bix⁶⁰ in 2002, in reviewing the many different aspects of legibility concluded that the individual elements of design and layout, do not determine legibility, but that sufficient legibility is the outcome of the sum of the parts eg font, font size, leading, colour etc