In today’s world, the LED display has been used for
presenting visual information under various circumstances. Such
information is an important intermediary in the human information
processing. Researchers have been investigated diverse factors that
influence this process effectiveness. The letter size is undoubtedly
one major factor that has been tested and recommended by many
standards and guidelines. However, viewing information on the
display from direct perpendicular position is a typical assumption
whereas many actual events are required viewing from the angles.
This current research aims to study the effect of oblique viewing
angle and viewing distance on ability to recognize alphabet, number,
and English word. The total of ten participants was volunteered to our
3 x 4 x 4 within subject study. Independent variables include three
distance levels (2, 6, and 12 m), four oblique angles (0, 45, 60, 75
degree), and four target types (alphabet, number, short word, and
long word). Following the method of constant stimuli our study
suggests that the larger oblique angle, ranging from 0 to 75 degree
from the line of sight, results in significant higher legibility threshold
or larger font size required (p-value < 0.05). Viewing distance factor
also shows to have significant effect on the threshold (p-value <
0.05). However, the effect from distance factor is expected to be
confounded by the quality of the screen used in our experiment.
Lastly, our results show that single alphabet as well as single number
are recognized at significant lower threshold (smaller font size) as
compared to both short and long words (p-value < 0.05). Therefore, it
is recommended that when designs information to be presented on
LED display, understanding of all possible ranges of oblique angle
should be taken into account in order to specify the preferred letter
size. Additionally, the recommendation of letter size for 100%
legibility in our tested conditions is provided in the paper.
[1] G. C. Jorna, and H. L. Snyder, “Image Quality Determines Differences
in Reading Performance and Perceived Image Quality with CRT and
Hard-Copy Displays,” Human Factors and Ergonomics Society, vol. 33,
no. 4, pp. 459-469, Aug. 1991.
[2] A. Dillon, “Reading from paper versus screens: a critical review of the
empirical literature,” Ergonomics, vol. 35, no. 10, pp. 1297-1326, 1992.
[3] L. K. Henning, and N. Ye, “Interaction of sceen distances, sceen letter
height and soure document distance,” Interacting with Computers, vol.
8, pp. 311–322, 1996.
[4] H. Krueger, “Ophthalmological aspects of work with display
workstations” in E. Grandjean and E. Vigliani (eds) Ergonomic Aspects
of Visual Display Terminal, Taylor and Francil, pp. 31–40, 1980.
[5] H. Schmidtke, “Ergonomic design principles of alphanumeric displays,”
in E. Grandjean and E. Vigliani (eds) Ergonomic Aspects of Visual
Display Terminal, Taylor and Francil, pp. 265–270, 1980.
[6] M. G. Helander, and B.A. Rupp, “An overview of standards and
guidelines for visual display terminals,” Applied Ergonomic, vol. 15, pp.
185-195, 1784.
[7] American National Standards Institute (ANSI) Human Factor Society
(HFS) Joint Standard ANSI/HFS 100-1988, “American National Standard for Human Factor Engineering of Visual Display Terminal
Workstations,” in L.K. Henning, and N. Ye, Interacting with Computers,
pp. 311–322, 1996.
[8] Mil-Std 1472, “VUD letter height stadrad” in L.K. Henning, and N. Ye,
Interacting with Computers, pp. 311–322, 1996.
[9] United States Department of Transportation, “Human Factors Design
Guidelines for Advanced Traveler Information Systems (ATIS) and
Commercial Vehicle Operations (CVO)”, 1998. Available from:
http://www.fhwa.dot.gov/publications/research/safety/98057/ch03b.cfm.
[10] ISO Standard, “Font size,” The ergonomic working conditions: working
with computers, pp. 12, 2013.
[11] M.S. Sanders, and E.J. McCormick, Human Factors in Engineering and
Design, 7nd ed., McGraw-Hill, 1992, pp. 102-113.
[12] H. L. Snyder, J. J. Decker, C. J. C. Lloyd, and C Dye, “Effect of Image
Polarity on VDT Task Performance,” Human Factors and Ergonomics
Society Annual Meeting, vol. 34, no. 19, pp. 1447-1451, Oct. 1990.
[13] I.H. Shena, K. K. Shiehb, C. Y. Chaoc, and D. S. Leed, “Lighting, font
style, and polarity on visual performance and visual fatigue with
electronic paper displays,” in Displays, vol. 30, Apr. 2009, pp. 53–58.
[14] A. H. Wanga , and M. T. Chenb, “Effects of polarity and luminance
contrast on visual performance and VDT display quality,” in
International Journal of Industrial Ergonomics, vol. 25, May 2000, pp.
415–421.
[15] C. C. Lin, “Effects of contrast ratio and text color on visual performance
with TFT-LCD,” in International Journal of Industrial Ergonomics, vol
31, Feb. 2003, pp. 65–72.
[16] G. E. Legge, D. H. Parish, A. Luebker, and L. H. Wurm, “Psychophysics
of reading. XI. Comparing color contrast and luminance contrast,” in
Optical Society of America, vol. 7, 1990, pp. 2002-2010.
[17] JInternational Sign Association. Conspicuity and Readability, 2007.
Available from:
http://www.signs.org/portals/0/docs/signline/signline_51.pdf.
[18] American National Standards Institute (ANSI) Human Factor Society
(HFS) Joint Standard ANSI/HFS 100-1988, “American National
Standard for Human Factor Engineering of Visual Display Terminal
Workstations,” in S.J. Morrissey, “Readability of VDU Messages with
Oblique Screen Angles,” Advances in Industrial Ergonomics and Safety
I, pp. 337-343, 1998.
[19] M. B. Weinger, M. E. Wiklund, and D. J. G. Bonneau, Handbook of
Human Factors in Medical Device Design, Ed. Boca Raton: CPS Press,
2011, pp.342.
[20] Commission Internationale de l’Éclairage (CIE) 2001/ ISO 2002 Joint
CIE/ISO standard S008/E:2001/ISO 8995-1:2002(E): Lighting of Work
Places - Part 1: Indoor. Available from: http://www.tieathai.org/know/
general/general0.htm.
[21] Illuminating Engineering Association of Thailand, The basic knowledge
of illumination,” 2005. Available from: http://www.tieathai.org/know/
general/general0.htm.
[22] A. Colenbrander, Measuring Vision and Vision Loss, 2001. Available
from:
http://www.ski.org/Colenbrander/Images/Measuring_Vis_Duane01.pdf
[23] The Announcement Ministry of Education in Royal Thai Government
Gazette, Guidelines for optimizing the utilization building in institution,
130 Special Section 43, 2013, pp.15-21. [in Thai].
[24] T. Teoratanakul, Dictionary for Primary Education in Thailand,
Bangkok: P.S. Pattana, 2013, pp. 9-306.
[25] C. Karagoslo, C. Kampangtong and P. Phuriprinya, Entrance
Vocabulary Synonyms and Antonyms, Bangkok: P.S.P, 2001, pp. 5-141.
[26] M. Tangpijaikul, Vocabulary for Admission, Bangkok: The book, 2012,
pp. 31-151.
[27] Kaiser, Peter K. "Calculation of Visual Angle", in The Joy of Visual
Perception: A Web Book, York University. Available from
http://www.yorku.ca/eye/visangle.htm.
[28] G. Beattie and A. Ellis, “Learning to read”, in The Psychology of
Language And Communication, East Sussex: Prychology Press, 2010,
pp. 307-311.
[1] G. C. Jorna, and H. L. Snyder, “Image Quality Determines Differences
in Reading Performance and Perceived Image Quality with CRT and
Hard-Copy Displays,” Human Factors and Ergonomics Society, vol. 33,
no. 4, pp. 459-469, Aug. 1991.
[2] A. Dillon, “Reading from paper versus screens: a critical review of the
empirical literature,” Ergonomics, vol. 35, no. 10, pp. 1297-1326, 1992.
[3] L. K. Henning, and N. Ye, “Interaction of sceen distances, sceen letter
height and soure document distance,” Interacting with Computers, vol.
8, pp. 311–322, 1996.
[4] H. Krueger, “Ophthalmological aspects of work with display
workstations” in E. Grandjean and E. Vigliani (eds) Ergonomic Aspects
of Visual Display Terminal, Taylor and Francil, pp. 31–40, 1980.
[5] H. Schmidtke, “Ergonomic design principles of alphanumeric displays,”
in E. Grandjean and E. Vigliani (eds) Ergonomic Aspects of Visual
Display Terminal, Taylor and Francil, pp. 265–270, 1980.
[6] M. G. Helander, and B.A. Rupp, “An overview of standards and
guidelines for visual display terminals,” Applied Ergonomic, vol. 15, pp.
185-195, 1784.
[7] American National Standards Institute (ANSI) Human Factor Society
(HFS) Joint Standard ANSI/HFS 100-1988, “American National Standard for Human Factor Engineering of Visual Display Terminal
Workstations,” in L.K. Henning, and N. Ye, Interacting with Computers,
pp. 311–322, 1996.
[8] Mil-Std 1472, “VUD letter height stadrad” in L.K. Henning, and N. Ye,
Interacting with Computers, pp. 311–322, 1996.
[9] United States Department of Transportation, “Human Factors Design
Guidelines for Advanced Traveler Information Systems (ATIS) and
Commercial Vehicle Operations (CVO)”, 1998. Available from:
http://www.fhwa.dot.gov/publications/research/safety/98057/ch03b.cfm.
[10] ISO Standard, “Font size,” The ergonomic working conditions: working
with computers, pp. 12, 2013.
[11] M.S. Sanders, and E.J. McCormick, Human Factors in Engineering and
Design, 7nd ed., McGraw-Hill, 1992, pp. 102-113.
[12] H. L. Snyder, J. J. Decker, C. J. C. Lloyd, and C Dye, “Effect of Image
Polarity on VDT Task Performance,” Human Factors and Ergonomics
Society Annual Meeting, vol. 34, no. 19, pp. 1447-1451, Oct. 1990.
[13] I.H. Shena, K. K. Shiehb, C. Y. Chaoc, and D. S. Leed, “Lighting, font
style, and polarity on visual performance and visual fatigue with
electronic paper displays,” in Displays, vol. 30, Apr. 2009, pp. 53–58.
[14] A. H. Wanga , and M. T. Chenb, “Effects of polarity and luminance
contrast on visual performance and VDT display quality,” in
International Journal of Industrial Ergonomics, vol. 25, May 2000, pp.
415–421.
[15] C. C. Lin, “Effects of contrast ratio and text color on visual performance
with TFT-LCD,” in International Journal of Industrial Ergonomics, vol
31, Feb. 2003, pp. 65–72.
[16] G. E. Legge, D. H. Parish, A. Luebker, and L. H. Wurm, “Psychophysics
of reading. XI. Comparing color contrast and luminance contrast,” in
Optical Society of America, vol. 7, 1990, pp. 2002-2010.
[17] JInternational Sign Association. Conspicuity and Readability, 2007.
Available from:
http://www.signs.org/portals/0/docs/signline/signline_51.pdf.
[18] American National Standards Institute (ANSI) Human Factor Society
(HFS) Joint Standard ANSI/HFS 100-1988, “American National
Standard for Human Factor Engineering of Visual Display Terminal
Workstations,” in S.J. Morrissey, “Readability of VDU Messages with
Oblique Screen Angles,” Advances in Industrial Ergonomics and Safety
I, pp. 337-343, 1998.
[19] M. B. Weinger, M. E. Wiklund, and D. J. G. Bonneau, Handbook of
Human Factors in Medical Device Design, Ed. Boca Raton: CPS Press,
2011, pp.342.
[20] Commission Internationale de l’Éclairage (CIE) 2001/ ISO 2002 Joint
CIE/ISO standard S008/E:2001/ISO 8995-1:2002(E): Lighting of Work
Places - Part 1: Indoor. Available from: http://www.tieathai.org/know/
general/general0.htm.
[21] Illuminating Engineering Association of Thailand, The basic knowledge
of illumination,” 2005. Available from: http://www.tieathai.org/know/
general/general0.htm.
[22] A. Colenbrander, Measuring Vision and Vision Loss, 2001. Available
from:
http://www.ski.org/Colenbrander/Images/Measuring_Vis_Duane01.pdf
[23] The Announcement Ministry of Education in Royal Thai Government
Gazette, Guidelines for optimizing the utilization building in institution,
130 Special Section 43, 2013, pp.15-21. [in Thai].
[24] T. Teoratanakul, Dictionary for Primary Education in Thailand,
Bangkok: P.S. Pattana, 2013, pp. 9-306.
[25] C. Karagoslo, C. Kampangtong and P. Phuriprinya, Entrance
Vocabulary Synonyms and Antonyms, Bangkok: P.S.P, 2001, pp. 5-141.
[26] M. Tangpijaikul, Vocabulary for Admission, Bangkok: The book, 2012,
pp. 31-151.
[27] Kaiser, Peter K. "Calculation of Visual Angle", in The Joy of Visual
Perception: A Web Book, York University. Available from
http://www.yorku.ca/eye/visangle.htm.
[28] G. Beattie and A. Ellis, “Learning to read”, in The Psychology of
Language And Communication, East Sussex: Prychology Press, 2010,
pp. 307-311.
@article{"International Journal of Mechanical, Industrial and Aerospace Sciences:68450", author = "Photjanat Phimnom and Haruetai Lohasiriwat", title = "Preferred Character Size for Oblique Angles", abstract = "In today’s world, the LED display has been used for
presenting visual information under various circumstances. Such
information is an important intermediary in the human information
processing. Researchers have been investigated diverse factors that
influence this process effectiveness. The letter size is undoubtedly
one major factor that has been tested and recommended by many
standards and guidelines. However, viewing information on the
display from direct perpendicular position is a typical assumption
whereas many actual events are required viewing from the angles.
This current research aims to study the effect of oblique viewing
angle and viewing distance on ability to recognize alphabet, number,
and English word. The total of ten participants was volunteered to our
3 x 4 x 4 within subject study. Independent variables include three
distance levels (2, 6, and 12 m), four oblique angles (0, 45, 60, 75
degree), and four target types (alphabet, number, short word, and
long word). Following the method of constant stimuli our study
suggests that the larger oblique angle, ranging from 0 to 75 degree
from the line of sight, results in significant higher legibility threshold
or larger font size required (p-value < 0.05). Viewing distance factor
also shows to have significant effect on the threshold (p-value ", keywords = "Letter Size, Oblique Angle, Viewing Distance,
Legibility Threshold.", volume = "8", number = "12", pages = "2001-6", }
