1 Introduction
Most large print books in the UK are purchased from large print book producers by public libraries so these producers are dissociated from their users. Although libraries lack feedback statistics, they speculated that large print readers were generally happy with the large print books provided. Apparently readers only complained that the books were too heavy.
The majority of large print readers appear to be over retirement age (Bell, 1980). There is a strong positive correlation between visual impairment and age. Older age groups tend to have a higher incidence of visual impairment; Bruce et al. (1991) report 90% of visually impaired people are over 60 years of age. Macular degeneration and cataracts are age related and prevalent amongst large print readers (Bell, 1980) so it is not surprising that users prefer large print books because: of worsening sight; they are easier on the eyes; they can be read in bed; they are more restful; spectacles may not be needed; they are quicker to get through.
For a population with decreased visual capabilities, the design of typefaces for large print publications may determine their ability to access information and their enjoyment of the reading experience. This project focused on the design of typefaces in large print books where it appears the choice of typeface has not been based on scientific research. Generally there appears to be little scientific typographical research directly related to this user group. Legible large print requires more adjustment than merely increasing the scale of the typeface, as some typeface's characters look jagged at higher sizes. There is a tendency to use scaled up standard typefaces with fully justified text but this is unlikely to be optimal for large print book readers.
Most large print book producers in the UK (see appendix1) tried to be aware of their client's requirements but their previous user surveys were not available and most likely outdated. One company received no feedback at all from their end users. Large print producers think their readers prefer serif typefaces without hairline (thinner) character strokes. Although variants of Plantin or Times New Roman may have hairline strokes, they are used by Magna, Ulverscroft, Large Print Books, and Chivers Press. The National Association for the Visually Handicapped (NAVH) who have set standards for large print in America suggest using Helvetica. Big Print magazine uses 14 point Helvetica with 16 point leading. Matt paper is used to avoid reflections and glare.
Producers are under many constraints in large print book production e.g. the bigger the typeface, the bigger the book; to prevent 'bleeding' ink seeping though to the other side of a page, the paper needs to be thick but this also adds to the weight of the book. The book's weight is a major complaint by elderly people with arthritis. The design and layout (line lengths and margins) are constrained by the size of pages. Producers aim to maximise the amount of text per page which benefits readers due to a trade-off between the size and weight of a book will affect the legibility and readability of the books.
Variables related to the readers cannot be adjusted by the large print producers so indirectly act as constraints e.g. visual acuity, comprehension, alertness, practice, knowledge of the language, eye movement habits, attitude, purpose and environmental conditions such as level of illumination.
A few reports do not believe typeface design to be crucial because common typefaces are equally legible under normal conditions. Shaw (1969) declared the typeface is relatively unimportant compared with the effect of size and weight in terms of legibility. The 'Text matters' website (1998) reviews the choice of typeface as less important than the contrast, size, weight and spacing. Pyke (1926) found that typeface differences have to be radically different to affect legibility under normal conditions. Buultjens et al. (1999) nevertheless concluded that the font, size and style affected reading speed and accuracy.
McLean (1992) believes legibility research under the most scientific conditions has not come up with anything fundamentally different from that which typographic designers have developed with experience. But legibility research has been useful in specialised areas e.g. type for children, partially sighted people and the elderly.
One third of the large print book users tested by Bell (1980) were unable to read normal print. So two thirds were able to read ordinary print but despite this they chose to read large print. This indicates that even those who can read ordinary print may prefer to read large print. Acuity is the smallest stimulus size at which a visual task may be successfully performed. The legibility of text is unaffected by retinal size until it gets so small as to approach the acuity limit. Mansfield et al. (1996) conclude that for print sizes close to the acuity limit, the choice of typeface could make a significant difference in reading performance. Improvements to a typeface could be extremely beneficial to those with poor vision but unnoticeable to those with perfect sight.
The total retinal field of vision is 240°. The fovea is about 0.2mm in diameter or equivalent to ½°. It is connected to the greatest concentration of feature detectors and due to its high acuity, is instinctively used when reading. It was inferred that people with peripheral vision loss can still read ordinary print with their central vision. People with central vision loss e.g. if the fovea is impaired by macular degeneration, have to use their peripheral vision to read. Eccentric viewing involves using an intact (peripheral) retinal area to function in a similar way to the fovea. But with increasing retinal eccentricity, acuity decreases and stimuli are processed using less feature detectors. Peripheral vision is limited by two factors: the optical image quality and the receptor density on the retina (optics, 2001). Consequences of this are less ability to distinguish characters and a slower reading rate. Legge et al. (1996) deduced that the presence or absence of central vision predicts reading performance.
Some patterns recognition decline less in the periphery of the retina and involve different neural pathways (Latham, 1999). Due to differences in the structure of rod (foveal) and cone (peripheral) systems, information is processed differently therefore an optimum design may be dependent on the position of undamaged regions. Therefore the nature of the deficit determines the best design for an individual. From this it can be inferred that one typeface may not be suitable for all readers of large print books. Shaw (1969), Bell (1980) and Buultjens et al. (1999) believed it is not possible to design one typeface for all because there are so many eye conditions. Since optimum versions of a large print book cannot be produced for each visually impairment; the aim is to determine the most legible typeface for current and potential users of large print books. This project commences with the premise that by targeting the users, typefaces used in large print books could be improved for their readers.
A variety of visual impairments are prevalent amongst large print book readers and in many cases a reader may have more than one disorder. This investigation will regard visual impairments generally without specific reference to a particular disorder. This is based on the assumption that regardless of the individual's impairment, the print should be suitable for any reader.
Subtle differences in definitions make previous reports incomparable e.g. across reports legibility, visibility and readability can be equated. McLean (1992) elucidates 'legibility' implies distinguish ability (efficient recognition), visibility, clarity and ease of reading (disregarding the content). 'Legibility' as defined by Fabian (2000) is a measure of the recognisability of the characters, how easily they can be read, based on the visual appearance in a given environment, but this does not equate to reading speed. The reading speed is a function of many factors and there is little evidence that it equates to legibility. Even when there is no significant difference between commonly used typefaces reading speeds, can it be assumed their legibility is similar? 'Readability' defined by McNally (1913) is the extent to which a given type size or form lends itself to being read with the absence of visual effort. It can also be thought of as subjective ease and comfort to read. The subjective factor of ease is probably of great importance in reading (Zachrisson, 1965), readers opinions of accessibility are relevant measures of legibility. The context of usage will influence the legibility of a typeface so to appraise the typeface the purpose must be evident. The syntax, language and therefore comprehension were not a function of the typeface so were not relevant to this investigation.
MacKeben (2000) proposed that research aiming to optimise conditions for eccentric viewing should include optimising typographic design characteristics. He explained that, visually impaired people's reading difficulties demonstrated that compromised letter recognition impedes reading. There is a complex relationship between typographical factors, as gestalt principles dictate the whole is greater than the sum of its parts. This interaction between variables led Hill (1999) to declare "Perfect typography depends on perfect harmony between all of its elements". He also added "Comfortable legibility is the absolute benchmark for all typography". Subsequently within this investigation, typographic variables will be experimentally tested for legibility and feedback required again once a typeface has been developed from the combination of the variables.
Reynolds (1996) recommends a legible a typeface should have: a relatively large x-height in relation to the capital letter height; large open counters and a relatively generous set width; a lack of variation between thick and thin strokes; word spacing - the optimum will depend on letter and line spacing; line length - optimum is between 60 - 65 characters / line; the upper half of line delivers more clues to word form than the lower half. She also maintains that sans serif typefaces are less legible because serifs give horizontal emphasis that helps to hold the letter together as words and guide the eyes along the line (Gestalt principle of good continuation). Serifs add character thus distinction.
More specifically Page (2000) noted some findings for typefaces for partially sighted people. These requirements include: 16 - 20 point size; medium to semi-bold weight; a round body (with ample white space within); 2.5mm x-height; long ascenders and descenders; rounded small serifs are easy on the eye; 1.5/2 line spacing; 4 point leading; 1+ point kerning; 55 characters / line maximum; italics, capitals or fussy typefaces should be avoided; a typeface with clearly distinguishable characters is important; sans serif typefaces can give tramline effects i.e lll; and punctuation marks must be well formed.
After the main research had started, The American Printing House for the Blind (2001) announced they had developed APHont. Some characteristics of APHont include wider inter-character spacing, higher crossbars, sans serif characters, heavier letters and large punctuation marks. It has similarities with the typefaces in the Tiresias family.
1.1 Character Size
Due to traditional printing techniques, typefaces are measured in point sizes - one inch equals a point size of seventy-two. This represents the vertical size of the metal cast even though the character size on this face may vary, so printed typefaces with the same point size can differ in height. In this project the x-height will be used so typefaces can be compared. The x-height is the height of lower case letters such as the 'x' and 'o'. The taller the x-height of the characters, the more white space that can be incorporated into the body of the letter thereby improving the legibility (White, 1987).
Pyke (1926) stated for poor vision readers' differences in legibility diminish as the type size increases. Chung (2000) described how reading speed increased with print size up to a certain point then levelled off at a maximum reading speed. This occurs with both central and peripheral viewing. They also found that peripheral viewing requires a larger print size than central vision.
Due to size constraints of large print books, large print producers had researched the most appropriate size of print for use in their books and had found 16 point to be suitable. Although size is a crucial factor for VIPs ability to read, within this investigation all typefaces tested had an x-height equivalent to 16 point Times New Roman.
1.2 Increasing Legibility
Following is an introduction into some of the many factors that can influence a typeface's legibility specifically the character's form, degree of serif, weight and spacing. Hill (1999) states "First and foremost, the form of the letters themselves contributes much to legibility or its opposite". Differentiating parts of characters need to be simple and clear. Legibility is even more important for poor vision readers so when designing a typeface, attention will be paid to characters that are difficult to distinguish as mentioned below by previous research.
Cattell (1885) lists distinct letters as d k m q h b p w. Tinker (1928) reiterates that legibility is diminished by hair lines or long heavy serifs. He assigns high legibility to d m p q w, medium legibility to j r v x y and low legibility to c e i n l. Vernon (1931) found confusable letters include f & t, l & t, c & e, n & a, i & j, I & J. Most to least legible are k d q b p m w f h j y r t x v z c o a u g r i n s l. Ovink (1938) found the old style arched a and either form of g was acceptable. Burt (1974) maintains that distinguish ability is necessary between I l 1 ! i and h & b, C & G, Q & O, J & F, R & Q. Ighe (1988) found confusable letters include f & t, l & t, a & e, o & e and f i j l t ; and confusable capitals include B & R, C & G, O & C, O & Q, M & W. Generally verticals that are too close should be avoided e.g. U A V X Z. The middle horizontal line e.g. in E & F should be shorter than the top and not too thin.
For numerals Tinker (1928) found 3 5 8 2 to have low legibility. Ighe's (1988) confusable numerals are 3 5 8 0 6 2. Some least legible digits are 5 8 3 2 whilst the most legible are 7 4 1 6 0 9.
Letters can be are easier to read when in words than singly and out of context e.g. In Arial, lll could be roman 3, 111 or Ill (McLean, 1992). Legibility of letters and digits are possibly decreased when presented in a group, due to interference from adjacent characters. It is not valid to apply legibility results for single specific digits to continuous text reading situations.
McLean (1992) states that well designed roman type is easier to read than any fonts in the same family i.e. italics, bold, caps, expanded or condensed. Anything in italics is very difficult for partially sighted people to read. Tinker (1955) found that although italics decelerate reading by only a small amount, readers do not like them. A few oblique typefaces (sloped roman typefaces, not specially designed italics) are as easy to read as roman typefaces (McLean, 1992). Fancy typefaces are not legible, the more simple an outline is, the more legible the typeface.
In terms of print format, left justified text which is 'flush left / ragged right' is the easiest arrangement for the eye to read (White, 1987). The word spacing is constant and there is an even left edge for the 'return sweep'.
People read by patterns as well as by characters. Capitals (uppercase letters) are thought to be less legible due to the lack of variation in shape. They are appropriately used for headlines in a sans serif typeface. Lowercase serif typefaces are thought to be more legible for continuous text so might be better suited for general use, these theories are expanded upon below.
The Clovernook Center for the Blind (2001) prefer to use 18 point Tahoma which is backed by the American Printing House for the Blind and American Foundation for the Blind. Research by the American Printing House (Kitchel, 2001) asked subjects which typeface they preferred for reading continuous text, verdana emerged as the best typeface. Although this is not used in large print books, it may be an appropriate typeface for use in the questionnaire to subjects.
1.3 Serif or Sans Serif?
Fabian (2000) mentions that western culture has a serif bias possibly due to cultural preferences and educational preconditioning. In most of the world's languages, serifs don't exist. Despite this, serifs have three functions reports McLean (1992). Firstly they keep characters a certain distance apart. Secondly, they link letters to form words, which help reading by making shapes recognisable. Lastly, they help to differentiate individual letters particularly the top halves, which reveal more of the identity of the letters. Reynolds (1996) believes this makes sans serif typefaces less legible because they have less distinguishing features. Serifs also make a page look darker than they would appear in a sans serif typeface, this increases contrast and reduces glare (Hughes, 1998). Burt (1974) discloses three main types of serif:
It is thought that hairline serifs are equivalent to hair-line strokes which are not beneficial to partially sighted people. Slab serifs are full, solid serifs. Bracketed serifs accentuate the end of the stroke.
Evidence for and against the legibility of serifs is inconclusive. Fabian (2000) summarises ample research for and against both serif and sans serif typefaces. Arditi (2000), amongst others, found no significant difference in legibility between serif and sans serif typefaces. Taking environmental factors into account Yager et al. (1998) found in low illuminance levels, sans serif typefaces were read faster than equally sized serif text but Hay (1999) argues this could be due to varying stroke thickness in serif typefaces. Previous research does not clarify the type of serif being tested.
From a practical angle Love (1987) produced a booklet about how print designers don't always recognise the needs of visually impaired people. His booklet was printed in 14 point Plantin Roman because serif typefaces were thought to be more legible. Sans serif type Helvetica/Arial is widely used, especially for signs. Helvetica is appropriate for headings and short pieces but is difficult to read in extended text (Hughes, 1998). Generally, it is conceivable that as Ighe (1988) says sans serif typefaces are more readable in individual letters or words, whereas serif typefaces are more readable in sentences and longer passages. The reality is probably more complex especially where visually impaired readers are concerned.
1.4 Typeface Weight
For normally sighted readers, boldness does not speed up nor slow down the reading rate but is believed to be more illegible therefore should be used sparingly for emphasis (Paterson and Tinker, 1940). About a third as much light reaches a 60 year old retina than when the person was 20 years old (Gill, 2001). This has implications for the environmental conditions in which the literature is read and the weight of the typeface. Luckiesh and Moss (1942) report that the boldest type will reflect the least amount of light. So although high contrast is regarded as important, white space has to be maintained to balance the effects of glare (too light) and eyestrain (too bold). For each person these thresholds are likely to vary so an optimum weight may be an improbability. Another issue determined by Arditi et al. (1995) involves thickest stroked letters becoming less legible because gaps and other features are more difficult to resolve but a relatively large x-height may help negate this effect.
1.5 Spacing
Inter-line spacing, inter-word spacing and inter-character spacing are means to incorporate space into a typeface. There is a lack of previous research on spacing but it is very important because the eye is stimulated by the white of the background. Spacing must appear consistent, Hill (1999) states "Leading, letter spacing and word spacing must be faultless. Well spaced lines and words magnifies the beneficial effects of both". When spacing is too wide or too narrow it becomes arduous to read.
Leading is inter-line spacing (measured from baseline to baseline) so called due to traditional methods of inserting lead strips between lines to increase the space. Standard leading is the point size of the text plus two points e.g. 10/12 roman represents 10 point text with 12 point leading. Leading with the same point and text is called 'solid' (White, 1987) but this is not generally appreciated by readers. There should be more space between lines than between words (McLean, 1992) so words are associated horizontally not vertically and the eye is led along the sentence. Previous research such as that by Paterson and Tinker (1940) only studied leading with text size up to 12 points. It is thought that leading should be between 25% - 30% of the type size (Text matters, 1998; Arditi, 1999a). Because leading is a function of the print format not the typeface it will not be referred to in this report but can be investigated separately.
Inter-word spacing is depicted by a space character in the typeface. For fully sighted readers, close spacing benefits reading speed, it is also functional and economical. Gaps due to justification can disrupt the flow of reading, equally spaced words are easier to read (Swann, 1969) this reiterates the best format to use is left justification.
Crowding is noise from the interaction of adjacent characters which affects both letter and word recognition. Crowding effects at the acuity limit are thought to be due to neighbouring letters adding noise (Arditi, 1994) by falling within the receptive fields and thereby competing with the letter being processed (Cook and Cook, 1999). Logically, peripheral reading is easier when the spacing is also increased so crowding effects are negated. With more space, interference from adjacent letters is reduced but the visual span is smaller in the periphery. Therefore the spacing is an enigmatic parameter which makes inferences tricky.
To decipher this enigma Jacobs (1979) describes how low vision reading is sensitive to typefaces e.g. crowding effects are stronger if using peripheral vision. Arditi et al. (1995) also found crowding is worse with central vision loss so is potentially an influential factor on visually impaired people's reading capabilities.
Legge et al. (1997) state that visual span size is smaller using the periphery than when using the fovea. This is a factor that limits reading speed in peripheral vision. Chung (2000) found reading speed was highest at the fovea but decreased with eccentricity. She also maintains that crowding is an explanation for slow reading speed if using peripheral vision. Reading speed increased with letter spacing up to about the standard spacing, and then decreased slightly for larger spacing. This trend was similar across eccentricities and for small and large print sizes. Increased letter spacing beyond the standard size, which presumably decreases the adverse effect of crowding, does not lead to an increase in reading speed in either central or peripheral vision.
Inter-character spacing is determined by the pitch of the character which is the horizontal space per character. This can either be fixed/non proportional (same amount for every character) or variable/proportional (the spacing varies appropriately for each character). After the pitch has been set, when certain pairs of characters appear together they seem too close or too distant so the 'kerning' is adjusted to rectify this. Proportional spacing gives each letter the amount of space it needs to be most legible (Adobe, 2001). As with left justification, variable spacing produces equal space between letters it is also spatially economical and more aesthetically pleasing. Arditi has done the majority of research on 'pitch'. In (1990) he found that variable pitch yields better reading speed performance at medium and large character sizes because more characters are perceivable at each fixation. Hay (1999) states that overall one pitch style is not better than another: each pitch style is relevant in different situations. Arditi (1990) also mentions that fixed pitch was better for character sizes approaching the acuity limit. For those with macular degeneration, fixed pitch was more readable at the size at which they read most comfortably. This is possibly due to regular letter spacing creating positional certainty, which is reiterated by Disability Access Information (2001). Hay (1999) summarises that proportional spacing needs to be 15% larger than fixed width to share equal acuity levels. So for low vision people and reading near the acuity level i.e. central vision loss, fixed pitch may be read more easily than variable pitch due to crowding effects of the eccentric retina.
Continuous text introduces spacing issues i.e. leading, but producers have to be space conscious because of the weight and size constraints of the book. Books are read at various focal distances but cannot be comfortably held up due to their weight. This has implications for the size of the typeface so a trade-off between a large point size and the size/load of the book remains.
1.6 Punctuation
Although punctuation is often overlooked in other experiments, the shape and size will be herein investigated based on research that declared punctuation marks need to be bigger, enlarged beyond their present sizes (Ighe,1988). Prince (1968) specified full points should be at least 30% of the height of the lowercase 'o' and commas 55% of the lowercase 'o'.
1.7 Methods to Investigate Legibility
Various methods to investigate the legibility of print have been reported
by Tinker (1963)
and Zachrisson (1965).
There is little agreement between various methods used and results depend
on method chosen.
Techniques which were rejected in relation to this investigation are outlined
below, followed by those that were applicable. A tachistoscope could be
used to measure the speed of perception by timing the interval taken to
perceive a stimulus. This is useful to determine relative legibility but
it is not relevant to a normal reading situation. Eye movement methods
by direct observation or equipment are valuable but require access to
high-tech equipment. Unreliable data is produced from assumptions that
blink rate increases as legibility increases. For visual fatigue, Carmichael
and Dearborn (1947) found no significant difference even with prolonged
reading. Focal variator method uses a blurred image and the distance is
measured when the image becomes recognisable. But this differs from the
normal reading situation so is not appropriate. Luckiesh
and Moss (1935a) suggest heart rate is an unreliable measure as it
can be affected by many extraneous variables. A haloscope aids investigation
of ocular preference e.g. between sans and seriffed typefaces as used
by Zachrisson (1965).
Eye motion is not a suitable measure.
The distance measured from the book to the eye where print can be accurately perceived is useful to assess letter reading distance, but it is misleading if applied to normal prose reading. But it can provide an indication of whether readers are using character or word recognition. Although no correlation was found between preferences and legibility, people tended to read more aesthetic typefaces faster. The rate of work is the most satisfactory method by either: introducing a time limit and measuring the amount read; or imposing a work limit and measuring the time taken to read the passage. Comprehension would also have to be controlled so it does not become a confounding variable. Mackeben (2000) found his results showed no age dependence so the data generated in this investigation was combined and analysed as one group.
1.8 Critique
There is a lack of scientific typographical research standards for visually impaired readers. Measurements of different typefaces, have been made using different tools and protocols therefore results are inconsistent (Fabian, 2000).
The literature can also be misleading. Mansfield et al. (1996) found that reading acuity is better with Courier (sans serif, fixed pitch) than with Times (serif, variable pitch). There is a 10% slower reading speed with Times for visually impaired people. People may report that low vision readers have higher reading speeds with sans serif fixed pitch typefaces but this may be a generalisation if other factors such as the spacing are not controlled. Even if they are, the results may not be externally valid to other typeface combinations.
1.9 Criteria for a Large Print Book Typeface
Regarding the typographical research and constraints imposed by a large print book enables specification of design criteria of a large print book typeface to be addressed. The characters need to be very easily distinguished from each other i.e. I l 1! This can be achieved by lengthened ascenders and descenders, by ample white space within and around characters and a large x-height in relation to capital letter height. This will also prevent character's features losing their distinguish ability if the weight of the typeface is increased.
The variables outlined below were kept constant during the whole investigation so only the variable being tested was varied. Fancy typefaces were avoided because familiar recognisable characters are the most easily discernable. Hyphenation was kept to a minimum especially at line ends. Typefaces did not have thick and thin strokes (hairlines). Left justification was used. No all caps were used in the continuous text. No italics or underlining were used. The samples were printed on matt opaque white paper with black ink to provide contrast. Off white paper could also have been used to reduce glare. All the typefaces had the same x-height as 16 point Times New Roman. The optimum of 55-60 characters per line was adopted. Leading was adjusted so all the samples occupied the same amount of vertical space on the page, ideally 25% of the point size or 2 point sizes should have been added. Word spacing should be 2mm between words or equivalent to the lower case c. The kerning was adjusted for certain pairs of characters e.g. 'cl, rn and ll' so they did not look like 'd, m and U' respectively.
1.10 Experimental Hypotheses
Initially, to determine if currently used typefaces are regarded as the most legible by large print readers, they will be tested against each other. So for the first part of the investigation to find the 'most legible typeface', the null hypothesis states that there is no significant difference in legibility between the typefaces.
The second hypothesis relates to the 'degree of serif', it is thought that for visually impaired readers, a sans serif typeface is more legible than a seriffed one. It is also thought that the legibility will decrease with an increase in the degree of serif.
Based on the evidence provided, hypothesis three about the 'inter-character spacing' states that the wider the spacing the more legible the typeface for visually impaired readers.
The fourth hypothesis in relation to the 'weight' of the typeface assumes that the bolder the typeface the more legible it is to visually impaired large print readers. This is thought to be due to an increase in contrast which is especially important for older readers.
The fifth hypothesis as presented by previous research states that the more pronounced the 'punctuation marks', the more legible visually impaired large print readers will find them.
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