社会医学研究．第 34 巻 1 号．Bulletin of Social Medicine, Vol.34（1）2017

原著

How Well the Elderly Evaluate the Readability of E-paper Devices: The
Effects of Font Sizes
高齢者は電子ペーパー機器をどのくらい読みやすいと評価しているか？
---- 文字サイズの効果について
Paul Lege1), Shigusa Matsunami1), Takehito Kojima2), Masaru Miyao1)
1) Nagoya University, 2) Chubu-Gakuin University

Abstract
The purpose of this experiment was to measure and understand reading tests how the elderly evaluated theeffects of the three font sizes using the Courier typeface from two different displays. The two devices included
the E-paper device (Amazon Kindle Deluxe TM) and a backlit LCD (Apple iPad TM). These were compared toconventional paper as a reference. The study involved 99 participants of various ages, who were given a shortreading task that measured for speed and a correct answer rate from different sets of font sizes of 8 pt (2.75 mm),
12 pt (3.25 mm), and 16 pt (5.75 mm). After each task, the readers rated the readability of visual performanceof the device at each of these point sizes. Our study found that the readability of the E-paper was equal to theperformance of paper text. Therefore, E-paper designed to function similar to paper can contribute to improving
readability including magnification function, especially for the elderly. On the basis of this study, we recommend a
default setting higher than 8 pt (2.75 mm) be displayed on the screens of E-papers.

抄録
この実験の目的は、電子ペーパーに表示された文章を読む課題について、高齢者を含む多数の実験参加者によって、どのくらい電子ペーパー機器の読みやすさを評価しているかについて検証したものである。2 種の情報機器（電子ペーパーのアマゾン・キンドル・デラックスとバックライト型液晶のアップル・アイパッド）を使用し、クーリ
エ・フォントを使った 3 つのフォントサイズの効果を評価した。対照として従来の紙も比較にために用いた。実験には、幅広い年齢層を含む 99 人の実験参加者が調査された。彼らは、短い読み課題を与えられた。このテストは8pt（2.75mm）、12pt（3.25mm）、および 16pt（5.75mm）のフォントサイズの文字を読ませ、スピードと正答率を測定した。個々の機器や紙での読み課題の後に、参加者は、機器や紙のそれぞれ３段階の文字サイズごとに、読みやすさを評価した。その結果、情報機器の読みやすさは、紙と同等であることがわかった。
したがって、紙とよく似た性質を有する電子ペーパーは、文字も拡大も容易で、高齢者にとって、読みやすさを改善することに寄与できる。この研究に基づいて、私達は、電子パーパーの画面において、8pt（2.75mm）の文字
高を最低基準とする読みやすさに関する設定を推奨する。
Keywords: Readability of E-paper, Font Sizes, Aging, Standards
キーワード：電子ペーパー、フォントサイズ、高齢化、読みやすさの標準化

1 Introduction

have arisen regarding their functionality relative

Conventional books have a long history of global

to conventional paper, especially, e-paper devices.

publication, while the development and spread of

The readability of liquid crystal displays were fully

e-books has only been present over the two decades.

surveyed till now, but e-paper using e-ink has not

The use of e-book readers has spread remarkably andbeen tested on readability.

appears to be expanding for all ages, but questions－ 71 －

社会医学研究．第 34 巻 1 号．Bulletin of Social Medicine, Vol.34（1）2017

2 Methods

DeluxeTM), a backlit LCD (Apple iPadTM), and as

2.1 Participantsa reference, conventional paper text (with the text

The participants for this experiment included 99

printed on PPC paper of 69 % whiteness)1,2). Table 3

males and females between the ages of 15 and 76

below shows the shows the general specifications foryears (M 46.7, SD 14.7). Participants who usuallydetails each mode of delivery of the text.

wore glasses or contact lenses used them for theexperiments. We obtained informed consent fromall the participants and approval for the study fromthe Ethical Review Board of the Graduate School ofInformation Science at Nagoya University.
Table 1 below shows the number of participants
divided into four general age groups. The participants
were divided into four groups by age: young (29 years
and younger), middle-aged (30 to 44 years old), senior
middle-aged (45 to 64 years old), and elderly (65 years
and older).

In order to avoid reader bias from brandrecognition, the participants read from a bezel
covered with white Kent paper with only the screen
showing. The test media or test paper was mounted
on the center of a board. The text displayed on eachmedium was set at the same height. The front lightlevel of the KV and the back light level of the iPadwere set to maximum levels. The text color was
black/dark, and the background color was white/bright.
Figure 1 shows the screen luminance of each

We measured the participants’ lens cloudiness with

device. The screen luminance for the iPad was muchan Anterior Eye Segment Analysis System (NIDEK

higher than for the paper text and Kindle Delux (DX),

EAS-1000). The typical gradation in the range ofsuggesting that it would perform better outdoors

cloudiness is from 0 to 250 with the higher number

than indoors. We then calculated the contrast ratios

representing greater cloudiness Table 2 below

from the measured values of the brightness of theshows the measured values of the readers divided

background color and text color (Figure 2). The DX

into age groups. The youngest group had sufficient

showed results on the screen luminance similar toamplitude of lens accommodation. The middle-aged
group had sufficient near vision ability, although theiraccommodation was slightly weaker. The senior
middle-aged group had mild presbyopia and problems
in near vision work. The elderly group had typicalpresbyopia and generally had to wear glasses for
close vision.

2.2 Experimental design
For this experiment, we used three types ofreading terminal devices, an e-paper (Amazon Kindle－ 72 －

社会医学研究．第 34 巻 1 号．Bulletin of Social Medicine, Vol.34（1）2017

out the experiment at about the 1,000lx level ofilluminance by using a 6500 K LED light sourcewith a fluorescent lamp that had a uniform color
temperature. The International Organization ofStandards (ISO) recommends an illuminance levelof 1,000lx for doing precision work in an office4). The
headrest for the participant’s forehead was kept at avisual distance of 400 mm. The participants looked at
the devices at an angle of about 100 degrees to

2.2 Task design
The experimental task was a block reading testof a short duration (Figure 4). The display format
conformed to that used for evaluation of electronic
conventional paper. The iPad had a higher contrast
ratio compared to the other devices because it
showed a lower screen luminance of black/dark anda higher screen luminance of white/bright.
We put the reading devices into a compartmental
lighting system placed on a desk within a darkened
room (Figure 3). We created this lightning systemwith reference to a previous study 3). We carrieddisplay devices by the International Organization forStandardization (ISO)5). We used random alphanumeric
text and unified the size of the characters. The
font type was Courier for because it is a uniform
monospaced font that has a slight serif (“bearded”)
which may be of some help to the elderly in readingfrom e-papers. A monospaced font is one with a fixedwidth; that is, each letters occupies the same amountof horizontal space6).

As the width of the characters for Courier isuniform, our focus was with the height of the fontsize. For the first experiment, the font sizes were set
at 8 pt (approx. 2.75 mm height), 12 pt (3.25 mm), and16 pt (5.75 mm). Figure 4 below shows the exampleof the text blocks for the reading task. The readers
performed nine tests (three font sizes per each of thethree devices) in which they read the text silently－ 73 －

社会医学研究．第 34 巻 1 号．Bulletin of Social Medicine, Vol.34（1）2017

from the top left and then we measured the total

3 Results

time that it took to complete the procedure.

3.1 Experiment

The participants were asked to count the number

Table 4 below shows the results from the two-of capital letter“M ”s in the total text with a counterway ANOVA for participants’ evaluation (VAS),

device as they read through the characters. We

reading time index, and correct answer rate index.

calculated the correct answer rate from the number

The VAS showed significant differences among both

“M ”s that the participants found and the actual

the types of devices and the font sizes. No two-factor

number of“M ”s in the text. The correct answer

interaction was observed among these fonts. For

rate was not entirely exact because the participantsreading time index, no significant differences weresometimes misread other alpha characters as large

observed among the types of device of the font sizes.

“M ”s.

The correct answer rate index showed significant

The reading time index and correct answer rateindex were divided by the average values of each of
the participant’s actual values in order to standardize

differences among the font sizes.
Table 4. Two-way ANOVA for the VAS, reading timeindex and correct answer rate index
Source

Df

SS

MS

F

the participant’s performance. A high-scoring reading

VAS

time index meant that it took the participant a

Types of devices(D)27030.473515.23

7.94**

long time to read. The high scoring correct answer

Character sizes(C)284091.9642045.98

94.96

**

rate index meant that there was a large number of

D×C
Reading time index

4

174.48

43.62

0.10

Types of devices(D)

2

0.004

0.002

0.226

2

0.001

0.000

0.028

4

0.045

0.011

1.163

2
2

0.032
0.330

0.016
0.165

0.851
8.732

4

0.404

0.101

5.334

correct answers.

Character sizes(C)After each reading, the participants also evaluated

D×C

the readability of the texts using a Visual Analog

Correct answer rate index

Scale (VAS). We converted the values of the VAS

Types of devices(D)into a 100-point scale in the final analysis. Figure 5

Character sizes(C)D×C† **; p<0.01

provides an example of a subjective evaluation using
the VAS method. A high-score on the VAS meansa device was very readable. A score of zero (0) as**

Table 5 below shows multiple comparisons

missing values when participants could not read or

between the VAS and correct answer rate index. The
Table 5 below shows multiple comparisons between the VAS and corr
VAS scores for 8 pt (app. 2.75 mm) were significantly

when the reading time at the answer rate could notrate index.
The VASfor 8 ptfont(app.sizes.
2.75 mm)significantly lower colowercomparedto scores
the higher
ThewereVAS

be scored.

scores for the DX were significantly lower thanthe higher font sizes. The VAS scores for the DX were significantly lower ththose of the iPad and Paper. The correct answer rate

the iPad and Paper. The correct answer rate indexes for the 8 pt size were si
lower than those of more than 12 pt (3.25 mm) size.

We used a two-way analysis of variance (two-way
ANOVA) as a statistical method to evaluate the final
results. According to the age grouped analysis, we
also used a one-way analysis of variance (ANOVA)
and the Scheffé multiple comparison procedure inorder to check the differences between the agegroups.
－ 74 －

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社会医学研究．第 34 巻 1 号．Bulletin of Social Medicine, Vol.34（1）2017

indexes for the 8 pt size were significantly lower thanthere was no significant decrease in reading speed

those of more than 12 pt (3.25 mm) size.

and the correct answer rate. In addition, we wished toTable 6 below shows a comparison of the VAS

evaluate to what degree E-paper devices matched theby the font sizes for each age group using the one-functionality of paper text with respect the Courier font.

way ANOVA. The VAS scores for the DX at 12 pt

In this study, we conducted an experiment undersize were significantly lower than for the iPad. Table

1,000 lx of illuminance to eliminate the effect of

7 below shows a comparison of the correct answer

ambient illuminance on the readability of the e-paper

rate index by the font sizes for each age group using

and backlit LCD. The ISO also recommends more

the one-way ANOVA. The VAS scores for the iPadthan a level of 500 lx for indoor reading 4). In ourat 12 pt size were significantly lower than that of theprevious studies, we found no significant differences

Paper. No significant difference for the reading timeon the readability of an e-paper, LCD, and paper at

index was observed between the font sizes and types

the 1,000 lx level7.8).

of devices. Finally, no significant difference for allindexes were observed among the age groups.

We used the Courier font type because it is amonospaced font recommended for such studies
by the ISO6). In addition, in order to conform to ourprevious studies, we measured the character heights
in millimeters to ensure compatibility. Studies havereported that Courier is a viable font for the elderly
suffering with vision problems including maculardegeneration10).
In this experiment, we focused on the e-paper’s
font features as a display media and how they may
effect readability for various ages. We also compared
the e-paper and paper with the backlit LCD which
are currently available on the market. We referred
to previous studies in order to set the experimental
text font sizes10,11). We set the text font sizes at threelevels; 8 pt (character height: 2.75 mm), 12 pt (3.25mm), 16 pt (5.75 mm).
The reader evaluations showed scores above 45 (ona scale 0 to 100) for each device and font size. In ourprevious studies, we suggested establishing a baseline
score of 45 for VAS to indicate whether participants
reached a certain level of proficiency in reading atext13,14).

4 Discussion
In this study, participants of different ages took
a silent reading test to evaluate the readability of
three different font sizes used on e-paper device andliquid crystal display with the Courier font type. The

The e-paper showed no significant differencecompared with other devices for the reading timeindex and correct answer index. No significant
differences for each character size were observed

aim was to focus on what was the minimum fontamong age groups. All the devices were readable atsize that various ages of participants could maintain in

about the 8 pt size which supports previous studies

their reading performance; that is, testing to see thatthat looked at visual performance and fatigue15,16).

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社会医学研究．第 34 巻 1 号．Bulletin of Social Medicine, Vol.34（1）2017

5 Conclusion

6）R. Stroud, “Courier Fonts: Everything you

This study investigated the effects of font sizes andwanted to know about courier fonts,” (n.d)

aging on the readability of e-papers. We summarize(Retrieved October 2, 2016) http://www.

the findings as follows based on this and previous

rolandstroud.com/downloads/essays/studies and specifically focus on the use of thecourierfonts.pdf
7）T. Koizuka, S. Sano, T. Kojima, M. Miyao,

Courier font size used in each of the two devices.

5.1 Font sizes“Evaluating the Effects of Environmental(1) The screen font size (character height) that

Illuminance on the Readability of E-books,”SID

participants felt readable was more than 2.75 mm in

Symposium Digest of Technical Papers, 2013;height (8pt). We recommend a font size of more than44(1): 571-573
8）S. Matsunami, T. Koizuka, R. P. Lege, T. Kojima,

2.75 mm as a default size displayed on the screens of

M. Miyao ,“The Effects of Ambient Illuminancee-papers for all ages.
(2) All groups saw a decrease in reading speed

and Aging on the Evaluation of the Readability

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recommend this size as the minimum limit. The

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decrease was greater for those over 65 years of age.

5.2 Devices

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performed equally to paper text. However, e-books

11）D. Lee, Y. Ko, I Shen, C. Chao,“Effect of Light

are more advantageous because they allow the

Source, Ambient Illumination, Character Sizereader the opportunity to change the font sizes. Thisand Interline Spacing on Visual Performance andis particularly helpful for the elderly.

Visual Fatigue with Electronic Paper Displays,”
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works well for improving readability. Furthermore,

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