Marjukka Eloholma

Mesopic visual efficiency IV: A model with relevance to nighttime driving and other applications

The authors represent a research consortium1 which has adopted a task performance based approach for nighttime driving to establish a system for photometry in the mesopic region. This article analyses the experimental investigations described in earlier articles on visual performance in the mesopic domain using reaction time, detection threshold, and discrimination threshold techniques. These results are used to develop a system for mesopic photometry, which balances the quality of the fit to the experimental data with the ease of practical implementation by the lighting industry. A more complex model is also described, which takes account of the chromatic visual response channels and thus provides a better fit to some of the experimental results (particularly those involving monochromatic stimuli), but describes the totality of the data less well and is furthermore less suitable for practical photometric measurements.

Mesopic models : from brightness matching to visual performance in night-time driving: a review

At present, suitable methods to evaluate the visual effectiveness of lighting products in the mesopic region are not available. The majority of spectral luminous efficiency functions obtained to date in the mesopic range have been acquired by heterochromatic brightness matching. However, the most recent studies in the mesopic field have adopted a task performance-based approach. This paper summarizes the major mesopic models proposed so far, presenting in detail the experimental conditions of these studies. The authors represent a research consortium which has adopted the task performance-based approach for night-time driving in which mesopic visual performance has been divided into three subtasks. Data for each sub-task will be generated by using a set of common parameter values and 120 observers. The approach and methods used by the consortium are presented.

Visual Performance in Night-time Driving Conditions

This paper introduces an experimental multitechnique method which was developed to establish a basis for a task performance‐based mesopic photometry. This approach considers night‐time driving by dividing visual performance into three visual tasks, of which achromatic threshold and reaction time are presented. The performance of both visual tasks decreased with decreasing luminance level from 1 to 0.01 cd m−2, showing the strong effect of light level on visual performance in driving. The behaviour of the achromatic contrast threshold and reaction time for low‐contrast targets was similar in terms of spectral effects, the strongest effects occurring at the lower mesopic levels. Both measures showed the Purkinje shift with decreasing luminance levels. The experimental data were used to calculate mesopic performance measures with the new mesopic model. The results imply that compared with V(λ), spectral sensitivity in night‐time driving can be better described with a mesopic model based on visual performance measures.

Modeling spectral sensitivity at low light levels based on mesopic visual performance.

The spectral sensitivity of the eye at low light levels, ie, mesopic conditions, is determined by the rod and cone photoreceptors of the retina operating together in varying degree as adaptation luminance shifts between the scotopic and photopic. Thus mesopic spectral sensitivity is different from photopic, where only cones contribute to vision. There are definite needs for a practical system of mesopic photometry to be used in assessing light at low light levels, especially in road and other outdoor lighting applications. However, neither of the recently proposed systems of mesopic photometry, the MOVE-model or the X-model, is found satisfactory by common consent of the lighting community. The most active debate has considered the upper luminance limit of the mesopic region, which is regarded to be too high for the MOVE-model and too low for the X-model. The present paper proposes a new modified MOVE-model whose upper luminance limit is adjusted to meet the actual road and street lighting luminance values measured in different weather conditions. The paper compares the MOVE-model, X-model, and the proposed modified MOVE-model with three independent visual performance data sets provided by different European universities. Based on the comparison, recommendations are given for future actions towards internationally accepted practice for mesopic photometry.

Analysis of Road Lighting Quantity and Quality in Varying Weather Conditions

Abstract This article focuses on road lighting measurements and calculations. Road lighting measurements are made to study the definition of appropriate road surface luminance levels during different weather conditions. Measurements took place in five pilot locations where the effects of snow, rain and fog on road luminances were examined. Through the measurement results, the effects of weather on road luminances are introduced and analyzed. The characterization and investigation of different weather conditions and their effects on visual conditions in driving offer new ways to optimize intelligent road lighting control and to make it more efficient. With an effective road lighting control system and real-time luminance measurements, electricity can be saved without adversely affecting either the safety of driving or the quality of road lighting.

Authors’ response to SA Fotios

three sub-tasks: can it be seen, how quickly, and what is it. This provides a useful framework for devising the experimental work. Would the authors please confirm whether the proposed reaction time tests will be onaxis, off-axis, or both. Also, it is noted several times that their work will use 120 observers: is this particular quantity significant, and if so, why? I look forward to reading the results of the experimental work described in this paper.

Whiteness perception in Japanese and Finnish under cool and warm fluorescent lamps

In this study, we conducted the experiment to compare the whiteness perception of Finnish and Japanese observers. The rank order of perceived whiteness among seven nearly white Munsell chips (Value is 9.25 or 9.5, Chroma is 0, 0.5 or 1.0) under the fluorescent lamps of correlated color temperatures of 3000K, 5000K, and 6700K was determined. Observing condition employed in the two laboratories was exactly the same as well as the experimental procedure. In 3000K condition, the results of Japanese and Finnish observers agreed with each other quite well, while as the correlated color temperature becomes higher, the results from the two laboratories showed different tendencies. Negative correlation was found between the whiteness rank order and the metric chroma for all of the results.