Lighting and display screens: Models for predicting luminance limits and disturbance

An investigation of the level of disturbance caused by reflections from a variety of display screens, including interactive whiteboards, has been carried out using three test methods: Luminance adjustment, category rating and reading. The results from the luminance adjustment test and the category rating test were consistent, both showing similar significant effects of lighting-display parameters on the disturbance caused by screen reflections. In contrast, the objective measure of task performance in the reading test was barely responsive to reflections on the screens. Two models have been developed, one to predict the luminaire luminance at which 95% of observers were not disturbed by the reflections and the other to predict the rating of disturbance caused by reflections from the screens. Both models are based on lighting-display parameters including the size and luminance of the reflected light source and the specular reflectance, the effect of haze reflection and the background luminance of the display screen. These models can be used generally, to guide lighting recommendations and, specifically, to identify suitable luminaires to be used with given set of display screens or suitable display screens to be used with a given lighting installation

The effect of lighting on crime counts

The influence of lighting on crime was investigated by considering the effect of ambient light level on crimes recorded in three US cities for the ten-year period 2010 to 2019. Crime counts were compared for similar times of day, before and after the biannual clock change, therefore employing an abrupt change of light level but without an obvious intervention such as improving road lighting in an area. The results suggest a significant increase in robbery during darkness, confirming previous studies. The results also suggest darkness leads to an increase in arson and curfew loitering offenses, and to a decrease in disorderly conduct, family offences (non-violent) and prostitution. Future research investigating the effectiveness of improved street lighting should consider that this may not be beneficial for all types of crime

Judging the scientific quality of applied lighting research

Applied lighting research is inherently interdisciplinary. Any one study in which investigators seek to understand the effects of light may involve expertise drawn from fields as varied as psychology, physiology, photobiology, vision science, engineering, physics, horticulture, and architecture. Despite differences in the specifics of research methods, data management, data analysis, and presentation, the logic of scientific thinking is a common thread. This is the basis on which the peer review system operates. This article leads readers through the criteria used by journal reviewers and editors to determine the acceptability of papers for publication in a peer-reviewed journal. This is done by review of the 1941 paper by Kruithof in which he described the now-famous “Kruithof curve” relating preferred light source color temperatures and illuminances: How would one review the original Kruithof paper today, and what would we expect to be told about this work in order to judge the validity of the conclusions

Two-particle correlations in azimuthal angle and pseudorapidity in inelastic p + p interactions at the CERN Super Proton Synchrotron

Results on two-particle ΔηΔϕ correlations in inelastic p + p interactions at 20, 31, 40, 80, and 158 GeV/c are presented. The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The data show structures which can be attributed mainly to effects of resonance decays, momentum conservation, and quantum statistics. The results are compared with the Epos and UrQMD models.ISSN:1434-6044ISSN:1434-605

Brightness matching with visual fields of different types

Previous studies of spatial brightness have been carried out using a variety of visual fields, these ranging from a flat, uniform, neutral surface to interior spaces containing coloured surfaces and objects. It may be expected that this would affect judgements of spatial brightness under lamps of different spectral power distribution. This article presents the results of side-by-side brightness matching tests carried out using four different visual fields. It is concluded from interpretation of these data and results from previous studies that the presence of coloured objects or surfaces in the target field does not significantly affect the outcome of brightness matching trials

A comparison of simultaneous and sequential brightness judgements

This paper presents the results of brightness matching and brightness discrimination tests carried out using sequential evaluation (temporal juxtaposition) to compare brightness under lamps of different spectral power distribution at mesopic levels of illumination. These data are compared with the results of previous tests, which used simultaneous evaluations (spatial juxtaposition) to enable comparison of these different modes of evaluation. It is concluded that sequential and simultaneous evaluations yield similar estimates of illuminances required for equal spatial brightness and similar levels of precision in this task

Research methods to avoid Bias in categorical ratings of brightness

This article presents evidence of potential contraction bias in the category rating task associated with the stimulus presentation sequence, response range and response range anchors, and a grouping bias associated with the number of stimuli and response categories. These biases tend to reduce the difference between ratings given to stimuli. It is demonstrated that such bias is sufficient to hide differences in brightness under lighting from lamps of different spectral power distribution but that precautions can be taken to successfully counter the bias. Research methods that can be employed to avoid bias in categorical ratings of brightness are summarized

Predicting lamp spectrum effects at mesopic levels. Part 1: Spatial brightness

This paper reports on experimental work carried out to test metrics for predicting spatial brightness at mesopic levels under lamps of different spectral power distribution. The side-by-side matching technique was used following an extensive review of experimental design. Five different types of lamps were presented in all 10 possible pairs, these being selected to compare brightness predictions based on established characteristics of lamp spectrum such as colour rendering index, correlated colour temperature and the scotopic/photopic ratio. The results were also used to test proposed systems for predicting brightness and visual performance at mesopic levels. Of the lamp characteristics examined the scotopic/photopic ratio exhibited the highest correlation with the test results. The new CIE recommended system for visual performance based mesopic photometry was found to give an acceptable prediction of the brightness results

Evidence for response contraction bias in side-by-side matching tasks

A recent study of lamp spectrum effects at mesopic levels employed side-by-side matching to investigate brightness. The results revealed an unexpected effect, identified here as a response contraction bias, normally only expected when judging individual stimuli. Response contraction bias causes subjective responses to be biased toward the middle of a response range. Although the bias is small its effect on brightness matching can be significant if the test procedure does not employ appropriate counterbalancing

Count balancing needed to avoid bias in side-by-side brightness matching tasks

Spectral power distribution (SPD) is one of the variables that can be manipulated in lighting design. This article examines twenty previous studies which have investigated the effect of SPD on brightness using the side-by-side matching technique. Three sources of experimental bias are identified and are shown to be present in the majority of these studies, and hence must be considered to provide an unreliable estimate of the magnitude of the SPD effect on brightness. The first bias is associated with test participants' use of dimming control and two forms are apparent – a response contraction bias when the test is repeated at multiple reference illuminances and a conservative bias when the test is carried out at a single reference illuminance. The second bias is associated with the primary direction in which dimming must take place and the third bias is associated with the relative position of the stimuli within the apparatus