A shadow has two different attributes, harshness-softness and lightnessdarkness. A three-phase study designed to quantify these shadow characteristics has been carried out. In the first phase, numerous computer-generated examples of shadows were produced and their harshness-softness attribute was evaluated. The harshness-softness of shadows was graded based on the visual evaluation performed in this phase. In the second phase, the lightness-darkness attribute was graded depending on a calculation-based approach. In the third phase, a mock-up room office was constructed and various lighting scenarios created. The shadows produced under the different lighting scenarios were quantified using the results of the first and second phases. These quantities were then compared with people's judgements of the shadows on the work table. The general impressions of the subjects concerning the shadows on the work table as well as the appearance of faces were also collected. The grading of the shadows in the room based on the results of the first and second phases was found to be consistent with the subjects' evaluations.

Highlights:Graphical/Tabular Abstract  Investigation of modelling indicators  Comparison of the modelling indicators with each other  Comparison of the findings with the visual assessments of facial impressionThe appearance of objects' features like form, texture and human faces are examined under the heading 'modelling' in the literature and various modelling indicators have been proposed to define the appropriate conditions regarding modelling. Figure A. Calculation results for some lighting scenarios according to the proposed modelling indicators in literature Purpose:The aim of this study is to compare and evaluate different modelling indicators in two phases. Firstly, the comparison is based on different lighting scenarios that are created in a lighting software. Subsequently, calculated modelling indicators are compared with the visual assessments of a previous study. Theory and Methods:Modelling is a lighting design criterion and is described as the balance between directional and diffused light. The proposed modelling indicators were defined under certain lighting conditions. The calculation of the mentioned indicators for different lighting scenarios was therefore considered important. Thus, it may be possible to determine the indicator that may be considered most appropriate to be applied for any lighting arrangement. For this purpose, different lighting scenarios are generated in a model room created in the DIALux lighting program. The proposed indicators are calculated for each lighting scenario and the results are compared. The calculations are conducted for the eye height of a sitting person. The calculation results obtained in this phase are then compared with the visual assessments of facial impressions performed in a previous study. The model room created in the lighting program was the simulation of the mock-up room in which the visual assessments were performed. Results:The comparison of the calculated modelling indicators with each other showed that they are not coherent with each other. The calculation results were also not consistent with the visual assessments for each scenario. Conclusion:The results of this study showed that more research on modelling is needed. Identification of a modelling indicator is required to be used to determine the modelling condition for all possible lighting arrangements.

Çevremizde yer alan yüzeyler birer ikincil ışık kaynağıdır. Kendileri ışık üretmez, üzerlerine gelen ışığı yansıtır ve/ya da geçirirler. Saydam, yarı saydam ve saydamsız olan bu yüzeyler; parlak, ipeğimsi ya da donuk (mat) ve renkli ya da renksiz olabilirler. Yüzeylerin görünürlüğü, nesnel ve öznel olmak üzere iki şekilde değerlendirilebilir. Nesnel değerlendirmede, hesap ve ölçme yoluyla bulunabilen ve görünen tek ışıkölçümsel büyüklük olan ışıklılık rol oynar. Öznel değerlendirmede ise araç insan gözü olduğu için, insan gözünün fizyolojik yapısına bağlı olarak, görünürlük ışıksal uyartının logaritması olan parıltı ile belirlenir. Diğer bir deyişle, görünürlüğün öznel değerlendirmesinde, ışıklılığın ruhduyumsal karşılığı olan parıltı etkilidir. Işıklılığın/parıltının çok olması, yüzey görünürlüğünün daha fazla olmasına, kimi zaman kamaşma yaratmasına, az olması ise yüzeylerin etkisiz görünmesine neden olur. Bu çalışmada, görünürlük kavramı ve bu kavramı etkileyen büyüklüklerle ilgili bilgi verilerek, renksiz ve renkli donuk (mat) yüzeylerin nesnel ve öznel yönden görünürlüklerinin değerlendirilmesine yer verilmiştir.Anahtar sözcükler: Görünürlük, görünürlük çarpanı; ışıklılık; parıltı. Surfaces in our environment are secondary light sources. They do not produce light, but reflect or transmit the light that comes upon them. These surfaces which are transparent, translucent and opaque can be bright, silky or dull and coloured or colourless. The visibility of the surfaces can be assessed by two ways as objective and subjective. In the objective evaluation, luminance is affective which can be found by calculation and measurement and is the only photometric magnitude that can be seen. In the subjective evaluation, visibility changes as the logarithm of the visual stimulus depending on the physiological structure of the human eye. In other words, brightness that is the sensation of luminance (visual stimulus) is affective in subjective evaluation. The more luminance/brightness quantity, the more visibility of surfaces. But, it should be noted that high luminances create glare, low luminances provide ineffective surface visibility. In this study, visibility phenomenon and magnitudes that affect this phenomenon are explained, objective and subjective visibility of dull surfaces are examined.

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