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Print quality and visual performance
results are evidence against the widespread ergonomics concept that viewing distances to both screen and document should generally be about 500 ram. It is suggested that VDU users may select viewing distances that they find comfortable in the range of more than about 500 ram. 22.5.37 (121320)
Colombo, E.M., and Kirsehbaum, C.F. Print quality and visual performance. Lighting Res and Technol, 1990, 22.2, 8 5 - 9 3 , 25 refs. The print quality of reading and writing tasks affects the visual performance of observers. A set of 4760 results obtained with two kinds of task, word search and comparison of numerals, shows that the border definition of the marks is an important contributory parameter to high visual performance indices, while the influence of luminance is relatively weaker. At the same time assessment tests indicate that luminance is significant in defining the preferences of the observers. The tests were carried out with four levels of adaptation luminance: 15, 50, 1 l0 and 250 cd/m 2 .
22.5.38 (121323)
Kimura, K., Osumi, Y., and Nagai, Y. CRT display visibility in automobiles.
Ergonomics, 1990, 3 3 . 6 , 7 0 7 - 7 1 8 , 12 refs. Three experiments were carried out into aspects o f CRT display in the context of driving automobiles. The first focused on the combination of colours which renders information 'easy-to-read', and determined the relationship between luminance contrast and chromaticity difference. In the second, a background luminance which was not dazzling at night was expressed in a chromaticity diagram. In the third, the amount of information which can be read 'at-a-glance' was investigated. 22.5.39 (121324) Zhu, Z., and Wu, J. On the standardization of VDT's proper and optimal contrast range. Ergonomics, 1990, 3 3 . 7 , 9 2 5 - 9 3 2 , 10 refs. There are interactions in the effects of VDT luminance contrast and screen luminance on the operator's visual performance. The range of both optimal and proper contrast is the function of the level of background luminance on the screen. Increasing screen luminance results in a shift from optimal and proper contrast towards low contrast. The subjective
evaluation m e t h o d has the same validity as the performance index in assessing VDT display quality. 22.5.40(121325)
Fukuzumi, S., and Hayashi, Y. Luminance and stimulus purity of VDT display color in terms of readability. In t J Human-Compu ter Interaction, 1989, 1.2, 115-135, 19 refs. A study was undertaken to investigate the relations among luminance, stimulus purity, and Visual Display Terminal (VDT) display colour readability, and to clarify the relation between readability and eolour impression. F o u r levels of stimulus purity for orange, five levels for green, and five for purple, blue and white and black were examined by a paired comparison method and a questionnaire regarding impression observed for the colours under two levels of illuminance and three levels of luminance. Questionnaire replies indicated that each colour had an optimal stimulus purity, in terms of readability, which was from 0.2 to 0.5, independently from illuminance and luminance. Men's readability scores for higher stimulus purities than the optimal value, did not notably decrease, while women's scores were severely lower than the optimal value. In case o f short dominant wavelength, readability was higher under low luminance than under other luminances. By applying the Semantic Differential m e t h o d to answers to the questionnaire, 'Conspicuous factor' and 'Uncomfortable factor' were extracted, which were closely related to colour readability.
22.5.41 (121327)
Pastoor, S. Legibility and subjective preference for color combinations in a text. Human Factors, 1990, 32.2, 1 5 7 - 1 7 1 , 27 refs. This study examined legibility performance and subjective preference for text/background colour combinations displayed on a video monitor. Luminance contrast was fixed at two pre-optimised levels, either with text brighter than the background ( 10: I) or vice versa (1:6.5). In Experiment 1,32 subjects rated about 800 colour combinations. No evidence suggested differential effects of luminance polarity or hue, with the only exception that cool background colours (blue and bluish cyan) tended to be preferred for the light-on-dark polarity. Saturation had the most i m p o r t a n t influence on ratings. Any desaturated colour combination
appears to be satisfactory for text presentation. In Experiment 2 a reduced set o f 18 colour combinations was investigated with a new sample of 18 subjects. Reading and search times as well as multidimensional ratings were evaluated. There was no evidence for an influence of luminance polarity or chromaticity on performance. Subjective ratings corresponded well with the results of Experiment 1.
Workplace and equipment design 22.5.42 (121338)
Manning, D~., Jones, C., and Bruce, M. Proof of shoe slip-resistanceby a walking traction test. J Occupat Accidents, 1990, 1 2 . 4 , 2 5 5 - 2 7 0 , 9 refs. There is no universally acceptable or reliable method of measuring shoe and floor friction, and few of the many published methods are capable of measuring coefficient of friction (CoF) of shoes worn on the feet. A new walking traction test is described, in which a test subject walks on slippery floor surfaces, pulling against a set of springs and the maximum CoF, attained before the feet slip, is measured. Three soling materials were selected from a large number previously tested by a different method o f measuring CoF. One had registered higher than average CoF and the other two lower than average CoF. The three materials were moulded on to bowling shoes with flat soles and no separate heel or tread pattern. One set of three pairs was reserved for water-lubricated surfaces and the other sets for oily surfaces. Coefficient of friction o f the shoes was measured by the new walking test on three separate floor surfaces lubricated in turn with water and oil. The shoe soles were then abraded or polished in ten stages with an orbital sander. Surface roughness and CoF were measured after each abrasion treatment. With successive abrasion treatments, the soling selected for above average CoF gradually became rougher than the other two materials and it nearly always recorded higher CoF readings when tested by the walking traction method. Its superior grip was demonstrated at roughness readings above 15 microns on water lubricated floors; CoF of 0.43 was achieved on all three floors. The other two solings could n o t be roughened more than 15 microns. On oily surfaces, soling roughness of 21"5 microns only produced a CoF of 0-2. Permanent roughness of solings is one of the properties needed for safer walking in slippery conditions. This
Applied Ergonomics October 1991
353
Colombo, E.M., and Kirsehbaum, C.F. Print quality and visual performance. Lighting Res and Technol, 1990, 22.2, 8 5 - 9 3 , 25 refs. The print quality of reading and writing tasks affects the visual performance of observers. A set of 4760 results obtained with two kinds of task, word search and comparison of numerals, shows that the border definition of the marks is an important contributory parameter to high visual performance indices, while the influence of luminance is relatively weaker. At the same time assessment tests indicate that luminance is significant in defining the preferences of the observers. The tests were carried out with four levels of adaptation luminance: 15, 50, 1 l0 and 250 cd/m 2 .
22.5.38 (121323)
Kimura, K., Osumi, Y., and Nagai, Y. CRT display visibility in automobiles.
Ergonomics, 1990, 3 3 . 6 , 7 0 7 - 7 1 8 , 12 refs. Three experiments were carried out into aspects o f CRT display in the context of driving automobiles. The first focused on the combination of colours which renders information 'easy-to-read', and determined the relationship between luminance contrast and chromaticity difference. In the second, a background luminance which was not dazzling at night was expressed in a chromaticity diagram. In the third, the amount of information which can be read 'at-a-glance' was investigated. 22.5.39 (121324) Zhu, Z., and Wu, J. On the standardization of VDT's proper and optimal contrast range. Ergonomics, 1990, 3 3 . 7 , 9 2 5 - 9 3 2 , 10 refs. There are interactions in the effects of VDT luminance contrast and screen luminance on the operator's visual performance. The range of both optimal and proper contrast is the function of the level of background luminance on the screen. Increasing screen luminance results in a shift from optimal and proper contrast towards low contrast. The subjective
evaluation m e t h o d has the same validity as the performance index in assessing VDT display quality. 22.5.40(121325)
Fukuzumi, S., and Hayashi, Y. Luminance and stimulus purity of VDT display color in terms of readability. In t J Human-Compu ter Interaction, 1989, 1.2, 115-135, 19 refs. A study was undertaken to investigate the relations among luminance, stimulus purity, and Visual Display Terminal (VDT) display colour readability, and to clarify the relation between readability and eolour impression. F o u r levels of stimulus purity for orange, five levels for green, and five for purple, blue and white and black were examined by a paired comparison method and a questionnaire regarding impression observed for the colours under two levels of illuminance and three levels of luminance. Questionnaire replies indicated that each colour had an optimal stimulus purity, in terms of readability, which was from 0.2 to 0.5, independently from illuminance and luminance. Men's readability scores for higher stimulus purities than the optimal value, did not notably decrease, while women's scores were severely lower than the optimal value. In case o f short dominant wavelength, readability was higher under low luminance than under other luminances. By applying the Semantic Differential m e t h o d to answers to the questionnaire, 'Conspicuous factor' and 'Uncomfortable factor' were extracted, which were closely related to colour readability.
22.5.41 (121327)
Pastoor, S. Legibility and subjective preference for color combinations in a text. Human Factors, 1990, 32.2, 1 5 7 - 1 7 1 , 27 refs. This study examined legibility performance and subjective preference for text/background colour combinations displayed on a video monitor. Luminance contrast was fixed at two pre-optimised levels, either with text brighter than the background ( 10: I) or vice versa (1:6.5). In Experiment 1,32 subjects rated about 800 colour combinations. No evidence suggested differential effects of luminance polarity or hue, with the only exception that cool background colours (blue and bluish cyan) tended to be preferred for the light-on-dark polarity. Saturation had the most i m p o r t a n t influence on ratings. Any desaturated colour combination
appears to be satisfactory for text presentation. In Experiment 2 a reduced set o f 18 colour combinations was investigated with a new sample of 18 subjects. Reading and search times as well as multidimensional ratings were evaluated. There was no evidence for an influence of luminance polarity or chromaticity on performance. Subjective ratings corresponded well with the results of Experiment 1.
Workplace and equipment design 22.5.42 (121338)
Manning, D~., Jones, C., and Bruce, M. Proof of shoe slip-resistanceby a walking traction test. J Occupat Accidents, 1990, 1 2 . 4 , 2 5 5 - 2 7 0 , 9 refs. There is no universally acceptable or reliable method of measuring shoe and floor friction, and few of the many published methods are capable of measuring coefficient of friction (CoF) of shoes worn on the feet. A new walking traction test is described, in which a test subject walks on slippery floor surfaces, pulling against a set of springs and the maximum CoF, attained before the feet slip, is measured. Three soling materials were selected from a large number previously tested by a different method o f measuring CoF. One had registered higher than average CoF and the other two lower than average CoF. The three materials were moulded on to bowling shoes with flat soles and no separate heel or tread pattern. One set of three pairs was reserved for water-lubricated surfaces and the other sets for oily surfaces. Coefficient of friction o f the shoes was measured by the new walking test on three separate floor surfaces lubricated in turn with water and oil. The shoe soles were then abraded or polished in ten stages with an orbital sander. Surface roughness and CoF were measured after each abrasion treatment. With successive abrasion treatments, the soling selected for above average CoF gradually became rougher than the other two materials and it nearly always recorded higher CoF readings when tested by the walking traction method. Its superior grip was demonstrated at roughness readings above 15 microns on water lubricated floors; CoF of 0.43 was achieved on all three floors. The other two solings could n o t be roughened more than 15 microns. On oily surfaces, soling roughness of 21"5 microns only produced a CoF of 0-2. Permanent roughness of solings is one of the properties needed for safer walking in slippery conditions. This
Applied Ergonomics October 1991
353