Measured and perceived colour on cathode ray tubes

A study is outlined which indicates that the application of traditional colorimetry to CRT displays is not totally adequate. The findings may be interpreted as indicating that the measured colours of CRT displays are always more saturated than the colours perceived by the human eye.     

The effect of brightness on colour recognition under water

Abstract

Water distorts the colours of objects compared to the situation in air, and it is relevant to enquire how this affects divers' colour recognition. Twelve divers (eight in the laboratory and four in a field experiment) were required to determine the distances at which colours could be correctly identified in different types of water. Changing a target's brightness (keeping hue and saturation constant) significantly changed its recognition distance. In addition, reducing the reflectance of a target having a similar hue to that of the background reduced its recognition distance relatively more than targets with hues offset from that of the background. Consequently, classification by hue name alone was insufficient to allow an unambiguous rank ordering of the relative recognition distances of the different colours. In situ light measurements in the field study permitted the specification of the spectral characteristics of the targets and their visual background. Such data are important if a colour recognition model is to be established for situations involving gross spectral distortion.     

Automatic design support and image evaluation of two-coloured products using colour association and colour harmony scales and genetic algorithm

Colour plays a key role in determining a consumer’s response to a product’s appearance. Accordingly, this study proposes an automatic design support system which enables a designer either to emulate the colour scheme of a two-coloured product and then to determine its corresponding image perception, or to search for the two-colour combination which most closely meets the required image perception. The proposed system combines a gray theory-based colour-association evaluation method and a colour-harmony-based aesthetic evaluation method to design and evaluate different product-colour schemes. Since colour-harmony theories cannot be implemented directly using the additive primaries (i.e. R (Red), G (Green) and B (Blue)) used in most computer-based colour emulations, this study develops a RGB-based colour-association and colour-harmony measurement scheme to evaluate the image perception of a particular product-colour scheme. In an inverse process, a genetic algorithm is applied to search for the near-optimal colour combination which satisfies the specified product colour-association goal and achieves a high degree of colour harmony. Various case studies involving the design and evaluation of a two-coloured thermos flask are provided for illustration purposes to demonstrate the effectiveness of the proposed method.     

The effects of ambient illumination and target luminance on colour coding in a CRT display

In this paper, the effects of absolute colour-identification on a CRT display are compared under different experimental conditions, i.e., ambient illuminant intensity, colour temperature and target luminance. The results indicate that performance of colour identification deteriorated as ambient illuminant intensity was increased. Colour identification under the 2800 K colour temperature was better than that under the 1800 K and 5800K. Performance at high luminance was superior to that at low luminance. Colours were chosen to make up the colour coding system on the CRT display under various ambient illuminant conditions. The number and range of the colours selected for the colour coding could be expanded by increasing the target luminance on the CRT display.     

Perceptual correction for colour grading of random textures

We present a method of colour shade grading for industrial inspection of random textures, the differences of which are at the threshold of human perception. This method uses image restoration techniques to recover an unblurred version of the image, and then blurs it the same way as the human visual system does, to emulate the process of the image being captured by the human sensor. Subsequently, the colour image is transformed into a perceptually uniform colour space, where colour gra ding takes place. Received: 10 October 1998 / Accepted: 21 March 2000     

The colours are not on the display: a survey of non-veridical perceptions that may turn up on a colour display

Designers and users of colour-coded visual displays may be confronted by puzzling artefacts that are produced by the physiological mechanisms of visual perception. In this review I shall describe a variety of such visual oddities, discuss their nature, and provide suggestions for dealing with them. The phenomena to be discussed are small-field tritanopia, peripheral colour vision, the Bezold-Brücke effect, the Helmholtz-Kohlrausch effect, the Abney effect, chromatic induction, assimilation, the McCullough effect, the ‘fluttering hearts’ phenomenon, chromatic aberration, and colour stereoscopy.     

Quantifying and predicting the effects of basic text display variables on the perceived urgency of warning labels: tradeoffs involving font size,border weight and colour

Design variables surrounding the presentation of signal words in warnings have been previously shown to affect performance, or variables likely to be related to performance. The present study emphasized the signal word WARNING by presenting it in red, surrounded by a red border. It was at the head of an otherwise black pesticide label that used 8-point type. A study using 24 undergraduates investigated the effect of signal-word font size (8 to 32 points), white space around the signal word (2 to 32 points), and border width (1 to 8 points) on the rated urgency of the label. A measure of the aesthetic merit of each label was also obtained from nine design students and professionals. Seven levels of each variable were used, covering the practically-useful range of each variable in the circumstances. Results showed a linear relationship between each variable and perceived urgency, with text size having the greatest effect, followed by border width. It was shown that, within the variable ranges used, the perceived urgency of the emphasized signal word resulted from the sum of the urgencies associated with the separate dimensions used in the emphasis. Tradeoffs are discussed—for example an increase of 4 points in text size produced the same increase in urgency rating as produced by an increase in border width of 2-3 points. A second study, using a further 24 students, compared the red labels with labels in black only. It was found that the signal word had to be approximately twice as big in black as in red to give the same perceived urgency. Design implications of the finding that the most urgent labels are not necessarily the most aesthetically pleasing are discussed.     

The psychological effects on man of air movement and the colour of his surroundings

The psychological microclimate is a term which is used to describe the specific psychological effects of some environmental agents as well as the psychological effects of other factors of the physical environment (e g, colour of surroundings, etc). This paper considers air motion and colour schemes of space, defines their stress and strain factors, describes the psychological effects - post-strain, and the methodology of their investigation. It further suggests the criteria and limiting and optimum values of the dynamic effect of air (permissible air velocities in interior and exterior environments) and the colour scheme of space (in accordance with the Tektronix standard). In conclusion the paper sums up the possibilities of optimisation of the 'psychological microclimate'.     

The effect of text and background colour on visual search of Web pages

Usability and visual impact in Web pages are not necessarily compatible ideals. This paper investigates the effect of colour on the presentation of information in a navigation bar, and aims to contribute towards design guidelines for the use of colour on the Web. We studied the effect of the combination of text and background colour on visual search performance and subjective preference. Twenty-nine participants carried out a visual search task using mock Web pages. Analysis showed that higher contrasts between text and background colour led to faster searching and were rated more favourably. The results are discussed in terms of visual search processes and design recommendations are given.     

The influence of colour on CRT reading performance and subjective comfort under operational conditions

Performance and reports of comfort when proof-reading text displayed on a CRT were investigated as a function of the text/background colour. Luminances were those typically produced by commercially available hardware and software, and task conditions were designed to simulate those experienced by typical users. Colours from the extremes of the spectrum (red, blue) were shown to produce poorer reading performance, higher ratings of discomfort and a higher incidence of reported symptoms of discomfort than those from mid-spectrum and white stimulus conditions.     

Effects of cricket ball colour and illuminance levels on catching behaviour in professional cricketers

In recent years there have been many alterations to equipment and technology in professional cricket, including the introduction of white balls during day — night matches. In the present study simulated slip-catching performance and movement initiation time were examined in professional cricketers when ball colour and illuminance levels differed. Five male professional cricketers (mean age: 27.3 ± 1.4 years) volunteered to catch a total of 60 cricket balls, 20 (10 red and 10 white) under each of three illuminance levels (571, 1143 and 1714 lux). Balls were projected from a ball machine at 20 m s^?1 (45 mph) over a distance of 8.4 m, to the subject's dominant side. Catching performance was measured using an established catching scale. Movement initiation times for each hand were also calculated for each trial using a motion-analysis system. Data were submitted to separate two-way (ball colour [2] × illuminance level [3]) repeated measures analysis of variance. No significant effects were obtained for ball colour or illuminance levels for either catching performance or movement initiation time. Neither ball colour nor light level (within the range tested) affected slip-catching performance and movement initiation times in professional cricketers. Therefore it was concluded that the changes made to ball colour and light conditions in professional cricket were not detrimental to catching performance.     

Research on visual representation of icon colour in eye-controlled systems

Given the wide application of eye-controlled systems, the target population is not only people with a physical disability. The importance of design is increasing; no matter where the eye-controlled system is to be applied, research on the interface needs to keep up with system development. Based on the analysis of the characteristics of eye movement, and the interaction of eye-controlled systems and visual design principles, the aim of this study was to explore whether a change in the colour of the interactive elements in an eye-controlled system will affect the efficiency of a user's visual search. Based on the actual needs of the eye-movement interaction process in the eye-controlled system, we developed an eye-controlled interaction system using Unity software. Based on this system, we investigated whether a change in the colour of the interactive elements in the eye-controlled system interface was related to search duration. The experimental data verified that changes in colour saturation and brightness affected users’ search efficiency. When the saturation value of the icon colour was in the three ranges of 33% to 44%, 62% to 70, or 85% to 98%, reaction time was longest; the brightness value of the icon colour should be higher than 16%, and it is not recommended to be less than 5% under any circumstances. The experiment was combined with a questionnaire to quantitatively analyse participants' evaluation of the three types of feedback colours: reducing brightness, converting to the contrasting colour and converting to white. It was found that participants generally believed that the feedback form of reducing brightness was very natural, and the feedback form of converting to the contrasting colour was very clear. Moreover, it was found that participants of different ages had significant differences in the evaluation of feedback colour types. This study adds substantial evidence to the field of colour research in the visual representation of eye-controlled system interfaces.     

Effects of luminance and colour contrast on the search of information on display devices

For black-and-white alphanumeric information, the speed of visual perception decreases with decreasing contrast. We investigated the effect of luminance contrast on the speed of visual search and reading when characters and background differed also with respect to colour. The luminance contrast between background and characters was varied, while colour contrast was held nearly constant. Stimuli with moderate (green/grey) or high colour contrast (green/red or yellow/blue), and three character sizes (0.17, 0.37, and 1.26 deg) were used. Eye movements were recorded during the visual search task. We found that the visual search times, number of eye fixations, and mean fixation durations increased strongly with decreasing luminance contrast despite the presence of colour contrast. The effects were largest for small characters (0.17 deg), but occurred also for medium (0.37 deg), and in some cases for large (1.26 deg) characters. Similarly, reading rates decreased with decreasing luminance contrast. Thus, moderate or even high colour contrast does not guarantee quick visual perception, if the luminance contrast between characters and background is small. This is probably due to the fact that visual acuity (the ability to see small details) is considerably lower for pure colour information than for luminance information. Therefore, in user interfaces, good visibility of alphanumeric information requires clear luminance (brightness) difference between foreground and background.     

Application and experience of colour CRT flight deck displays

Colour CRT displays have the potential both to enhance the presentation of primary flight information and also to improve the interface between complex avionic systems and the flight deck crew. This paper describes research to explore this potential, and reports the opinions of a wide range of pilots who experienced such displays in the working environment.     

After-effects of TFT-LCD display polarity and display colour on the detection of low-contrast objects

Participants performed a word–non-word discrimination task within a car control display emulated on a thin film transistor liquid-crystal display (TFT-LCD). The task simulated an information read-out from a TFT-LCD-based instrument panel. Subsequently, participants performed a low-contrast object detection task that simulated the detection of objects during night-time driving. In experiment 1, words/non-words were presented black-on-white (positive polarity) or white-on-black (negative polarity). In experiments 2 and 3, display colour was additionally manipulated. A positive polarity advantage in the discrimination task was consistently observed. In contrast, positive displays interfered more than negative displays with subsequent detection. The detrimental after-effect of positive polarity displays was strong with white and blue, reduced with amber and absent with red displays. Subjective measures showed a preference for blue over red, but a slight advantage for amber over blue. Implications for TFT-LCD design are derived from the results.

Statement of Relevance: When using TFT-LCDs as car instrument panels, positive polarity red TFT-LCDs are very likely to lead to good instrument readability while at the same time minimising – relative to other colours – the negative effects of an illuminated display on low-contrast object detection during night-time driving.     

Selection of character/background colour combinations for onscreen searching tasks: An eye movement,subjective and performance approach

The aim of the study was to investigate the effect of various character and background colour combinations on cognitive performance during onscreen searching tasks and to identify the best combinations with a multimodal approach of physiological (eye movement recording), subjective and performance data collection. In the absence of proper character and background colour combination the optimum performance for a cognitive task is greatly affected which in turn affects the productivity of the individual worker or communications among the operators working under the same network through information sharing. This study was designed by selecting six colours, i.e., white, black, yellow, red, blue, and green and subsequently combining them to 16 character and background colour combinations for a searching task. Right and left headed arrows were used as the character for the searching maneuver. Forty-four (N = 44) volunteers participated in the experiments. Various eye movement variables, legibility rating scale, NASA-TLX questionnaire, searching time and percentage of error were recorded. Subjects performed better wherever a good contrast was there because of a high legibility. A poorly contrasted display affected the physiological variables as well as subjective responses to negative directions. Among the combinations of dark character/light background, blue and red character on white background is highly recommended; and while that for light character/dark background, white is found to be the best character on blue and green backgrounds.     

Effects of environmental colour on males and females: a red or white or green office

This experiment assessed the effects of a red versus a green versus a white office environment on worker productivity and mood. An equal number of males and females completed a mood questionnaire before and after proofreading in one of the three offices. It was predicted that the subjects in the red office would report more tension and possibly make more errors. However, the subjects in the red office made the fewest errors, while the subjects in the white office made the most errors. Females scored significantly better on the proofreading task, and reporte mored tension and less vigour than males in the experiment. Subjects who worked in the red office found the colour of their office more distracting than subjects who worked in and rated the white office. The subjects in the white office reported that they would like to work in this environment and considered this colour most appropriate for an office. The authors speculate that a sterile, white environment may not be as conducive to work as is believed.     

New methods for analysing colour texture based on the Karhunen-Loeve transform and quantification

In this article, we offer an original study on the analysis of the texture of colour images based on Local Linear Transforms (LLT). Our colour approach is based on the separability of the data which reduces the number of texture parameters. We also propose the extension of Run Lengths (RL) and Co-occurrence Matrixes (CM) to colour images. In this respect, two different ways were explored (data merging and quantification). We finally present a comparative study showing the efficiency of the first method (LLT) as well as the complementary nature of the other methods (RL, CM).