Pub Date : 2021-07-07DOI: 10.1080/15502724.2021.1921594
M. Rea, John D. Bullough, A. Bierman
ABSTRACT It is important in understanding the potential benefits of ultraviolet (UV-C) field applications for control of powdery mildew to know how long the lamps will last before replacement. We conducted a laboratory evaluation of a sample of low-pressure discharge germicidal UV-C lamps that have been used in field trials to control strawberry powdery mildew. None of the lamps tested failed to start after more than a year of operation. The degradation of UV-C output followed trends similar to those described by the manufacturer. Based on these measurement data and on the long history of this lamp technology, we predict that these lamps can continue to perform in the field after the manufacturer’s rated life of approximately 10,000 hours of continuous operation, by reducing the speed of application to deliver the prescribed UV-C dose. With protective sleeves, these low pressure discharge UV-C lamps can be expected to last for many years of service.
{"title":"Output Reduction over Time of Germicidal UV-C Lamps Used for Treating Agricultural Crops","authors":"M. Rea, John D. Bullough, A. Bierman","doi":"10.1080/15502724.2021.1921594","DOIUrl":"https://doi.org/10.1080/15502724.2021.1921594","url":null,"abstract":"ABSTRACT It is important in understanding the potential benefits of ultraviolet (UV-C) field applications for control of powdery mildew to know how long the lamps will last before replacement. We conducted a laboratory evaluation of a sample of low-pressure discharge germicidal UV-C lamps that have been used in field trials to control strawberry powdery mildew. None of the lamps tested failed to start after more than a year of operation. The degradation of UV-C output followed trends similar to those described by the manufacturer. Based on these measurement data and on the long history of this lamp technology, we predict that these lamps can continue to perform in the field after the manufacturer’s rated life of approximately 10,000 hours of continuous operation, by reducing the speed of application to deliver the prescribed UV-C dose. With protective sleeves, these low pressure discharge UV-C lamps can be expected to last for many years of service.","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"5 1","pages":"438 - 446"},"PeriodicalIF":3.6,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75971356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-03DOI: 10.1080/15502724.2019.1708204
R. Brémond
ABSTRACT The use of visual performance models in road lighting is an old idea: it was first proposed in the 1930s by Waldram with the Revealing Power, and by Roper and Howard who used the notion of visibility distance. The Visibility Level (VL) concept was then proposed by Blackwell, and the Relative Visual Performance by Rea and Ouelette. At the turn of the 21th century, some standards have considered using the VL in order to rate lighting installations through the Small Target Visibility concept. However, the use of visual performance indexes in lighting standards was recently withdrawed, which raises a question: what happened?
{"title":"Visual Performance Models in Road Lighting: A Historical Perspective","authors":"R. Brémond","doi":"10.1080/15502724.2019.1708204","DOIUrl":"https://doi.org/10.1080/15502724.2019.1708204","url":null,"abstract":"ABSTRACT The use of visual performance models in road lighting is an old idea: it was first proposed in the 1930s by Waldram with the Revealing Power, and by Roper and Howard who used the notion of visibility distance. The Visibility Level (VL) concept was then proposed by Blackwell, and the Relative Visual Performance by Rea and Ouelette. At the turn of the 21th century, some standards have considered using the VL in order to rate lighting installations through the Small Target Visibility concept. However, the use of visual performance indexes in lighting standards was recently withdrawed, which raises a question: what happened?","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"69 1","pages":"212 - 241"},"PeriodicalIF":3.6,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80277289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-03DOI: 10.1080/15502724.2020.1726183
C. Moscoso, K. Chamilothori, J. Wienold, M. Andersen, B. Matusiak
ABSTRACT Daylight provision to the indoor space is affected by different building elements that cannot be fully controlled by the users, such as the window size of a space. The dimensions of the fenestration not only affect the lighting levels, but they also affect how the space is perceived by its users. The present study examines three different window sizes via virtual reality, to study how they affect the perception of both a small and a large space at high latitudes. Additionally, two context scenarios (socializing and working), as well as three different sky types (overcast sky and clear skies with either high or low sun angle) were evaluated. The experimental study applied a mixed design with within-subjects and between-subjects factors. A total of 150 participants evaluated the scenes using a Likert-type scale to rate eight different subjective attributes. The statistical results showed that both window size and space type significantly affect the participants’ spatial perception, as well as their satisfaction with the amount of outside view. Larger windows led to more positively evaluated spaces for all studied attributes. Moreover, a significant interaction was found between window size and type of space for the satisfaction with the amount of view in the space, indicating that the window size was dependent on the type of space in which the windows are located. Specifically, the window sizes were rated higher in the small space than in the large space for the evaluation of amount of view. The findings show that window size affects how people perceive a space, and additionally, that other spatial features, such as space type, affect window size preferences.
{"title":"Window Size Effects on Subjective Impressions of Daylit Spaces: Indoor Studies at High Latitudes Using Virtual Reality","authors":"C. Moscoso, K. Chamilothori, J. Wienold, M. Andersen, B. Matusiak","doi":"10.1080/15502724.2020.1726183","DOIUrl":"https://doi.org/10.1080/15502724.2020.1726183","url":null,"abstract":"ABSTRACT Daylight provision to the indoor space is affected by different building elements that cannot be fully controlled by the users, such as the window size of a space. The dimensions of the fenestration not only affect the lighting levels, but they also affect how the space is perceived by its users. The present study examines three different window sizes via virtual reality, to study how they affect the perception of both a small and a large space at high latitudes. Additionally, two context scenarios (socializing and working), as well as three different sky types (overcast sky and clear skies with either high or low sun angle) were evaluated. The experimental study applied a mixed design with within-subjects and between-subjects factors. A total of 150 participants evaluated the scenes using a Likert-type scale to rate eight different subjective attributes. The statistical results showed that both window size and space type significantly affect the participants’ spatial perception, as well as their satisfaction with the amount of outside view. Larger windows led to more positively evaluated spaces for all studied attributes. Moreover, a significant interaction was found between window size and type of space for the satisfaction with the amount of view in the space, indicating that the window size was dependent on the type of space in which the windows are located. Specifically, the window sizes were rated higher in the small space than in the large space for the evaluation of amount of view. The findings show that window size affects how people perceive a space, and additionally, that other spatial features, such as space type, affect window size preferences.","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"94 1","pages":"242 - 264"},"PeriodicalIF":3.6,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89300367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-03DOI: 10.1080/15502724.2021.1933857
K. Houser
Quite a bit is known about group preference for how light sources render object colors, as distilled into Annexes E and F of TM-30-20 (ANSI/IES 2020). One area that is weakly substantiated, however, is group and subgroup preferences for how light sources render skin. This is a conspicuous shortcoming because people are intended to be the primary beneficiaries of lighting. Preference for the color rendition of skin is a challenging scientific problem with cultural implications. Skin spectral reflectance functions (SRFs) are generally reported as averages over a small area of skin, usually measured on some part of the arm or hand. While people with darker or lighter skin have variation in mean reflectance, the spectral features do not vary as much as one might expect (e.g., Angelopoulou 2001; Cooksey et al. 2019). The presumed implication is that it may be possible to predict reasonably well the color shift of a range of skin SRFs with a small number of samples. With skin, however, average shifts should not be expected to tell the whole story. If the color of a toy or piece of clothing is altered by a light source, it is not personal. But if a light source distorts a person’s skin in a way that is undesirable, then that is intrinsically personal. Evaluating skin rendition is further complicated because skin is not homogenous and cannot be represented in a single SRF, skin tone is dynamic based on blood flow and other factors, and preference varies with ethnicity, may vary with race, may be informed by culture, and may vary with individual characteristics. For example, some people may prefer the ruddier skin appearance associated with red-chroma-enhancing light sources, while others may not (e.g., those with neutral or cool undertones, mottled skin, or a skin condition). There is some evidence for cultural differences—e.g., some evidence suggests that, on average, Caucasians prefer a color-shift that causes a ruddier complexion more so than Asians (Wei et al. 2014). TM-30-20 does not include a specific design intent or design guidance related to skin appearance. This not because there is lack of interest, but because there is not enough knowledge to produce defensible recommendations. “More research is needed” is a common cry among researchers, but in this case the cry is true. It will be inspiring if future work includes an ethnically, racially, and culturally diverse research team that contributes to the conceptualization and design of new experiments, and a diverse set of participants that permits analyses based on ethnicity, race, and culture. This sort of granular information would provide deeper understanding of how different groups of people experience light and may open opportunities for spectrally tailored lighting solutions.
关于光源如何渲染物体颜色的群体偏好，如TM-30-20 (ANSI/IES 2020)的附录E和F中所提炼的，我们已经知道了很多。然而，群体和亚群体对光源如何渲染皮肤的偏好是一个缺乏证据的领域。这是一个明显的缺点，因为人是照明的主要受益者。肤色偏好是一个具有文化内涵的挑战性科学问题。皮肤光谱反射函数(srf)通常报告为小面积皮肤的平均值，通常在手臂或手的某些部位测量。虽然肤色较深或较浅的人在平均反射率上有变化，但光谱特征的变化并不像人们可能期望的那样大(例如，Angelopoulou 2001;Cooksey et al. 2019)。假定的含义是，它可能是有可能合理地预测一个范围的皮肤srf与少量样品的色移。然而，就肤色而言，平均班次不能说明全部情况。如果一个玩具或一件衣服的颜色被光源改变了，那就不是个人的。但如果光源以一种不受欢迎的方式扭曲了一个人的皮肤，那么这本质上是个人问题。评估皮肤状况更加复杂，因为皮肤不是同质的，不能用单一的SRF来代表，肤色是动态的，基于血流量和其他因素，偏好因种族而异，可能因种族而异，可能因文化而异，也可能因个体特征而异。例如，有些人可能更喜欢与红色色度增强光源相关的更红润的皮肤外观，而其他人可能不喜欢(例如，那些中性或冷色调，斑驳的皮肤或皮肤状况)。有一些证据可以证明文化差异。一些证据表明，平均而言，白种人比亚洲人更喜欢颜色的变化，从而使肤色更红润(Wei et al. 2014)。TM-30-20不包括与皮肤外观相关的特定设计意图或设计指南。这并不是因为缺乏兴趣，而是因为没有足够的知识来提出站得住脚的建议。“需要更多的研究”是研究人员的共同呼声，但在这种情况下，这种呼声是真实的。如果未来的工作包括一个民族、种族和文化多样化的研究团队，有助于新实验的概念化和设计，以及一个多样化的参与者群体，允许基于民族、种族和文化的分析，这将是令人鼓舞的。这种细粒度的信息可以让我们更深入地了解不同人群对光线的感受，并可能为光谱定制照明解决方案提供机会。
{"title":"Preference for the Color Rendition of Skin","authors":"K. Houser","doi":"10.1080/15502724.2021.1933857","DOIUrl":"https://doi.org/10.1080/15502724.2021.1933857","url":null,"abstract":"Quite a bit is known about group preference for how light sources render object colors, as distilled into Annexes E and F of TM-30-20 (ANSI/IES 2020). One area that is weakly substantiated, however, is group and subgroup preferences for how light sources render skin. This is a conspicuous shortcoming because people are intended to be the primary beneficiaries of lighting. Preference for the color rendition of skin is a challenging scientific problem with cultural implications. Skin spectral reflectance functions (SRFs) are generally reported as averages over a small area of skin, usually measured on some part of the arm or hand. While people with darker or lighter skin have variation in mean reflectance, the spectral features do not vary as much as one might expect (e.g., Angelopoulou 2001; Cooksey et al. 2019). The presumed implication is that it may be possible to predict reasonably well the color shift of a range of skin SRFs with a small number of samples. With skin, however, average shifts should not be expected to tell the whole story. If the color of a toy or piece of clothing is altered by a light source, it is not personal. But if a light source distorts a person’s skin in a way that is undesirable, then that is intrinsically personal. Evaluating skin rendition is further complicated because skin is not homogenous and cannot be represented in a single SRF, skin tone is dynamic based on blood flow and other factors, and preference varies with ethnicity, may vary with race, may be informed by culture, and may vary with individual characteristics. For example, some people may prefer the ruddier skin appearance associated with red-chroma-enhancing light sources, while others may not (e.g., those with neutral or cool undertones, mottled skin, or a skin condition). There is some evidence for cultural differences—e.g., some evidence suggests that, on average, Caucasians prefer a color-shift that causes a ruddier complexion more so than Asians (Wei et al. 2014). TM-30-20 does not include a specific design intent or design guidance related to skin appearance. This not because there is lack of interest, but because there is not enough knowledge to produce defensible recommendations. “More research is needed” is a common cry among researchers, but in this case the cry is true. It will be inspiring if future work includes an ethnically, racially, and culturally diverse research team that contributes to the conceptualization and design of new experiments, and a diverse set of participants that permits analyses based on ethnicity, race, and culture. This sort of granular information would provide deeper understanding of how different groups of people experience light and may open opportunities for spectrally tailored lighting solutions.","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"55 1","pages":"211 - 211"},"PeriodicalIF":3.6,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85238188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ABSTRACT It has been proved that lighting has nonvisual effects on the human body, including changes in heart rate and blood pressure. Heart rate and blood pressure are associated with the autonomic nervous system and can indicate stress level. The present study investigates whether heart rate and blood pressure are influenced by the frequency or duty cycle of pulsed light, together with the duration of lighting. Twelve healthy young subjects were recruited for the investigation. Subjects were exposed to pulsed light of varying frequencies (40 Hz, 100 Hz, 300 Hz) and duty cycles (10%, 50%, 90%). Exposure time was divided into two groups: short-time (20 min) and long-time (3 hours). Heart rate and blood pressure were measured during the experiments. Results showed that after a short lighting period (20 min), heart rate and blood pressure were significantly higher under 40 Hz pulsed than that under stable light, while 100 Hz and 300 Hz had no significant difference. After 3 hours of exposure time, the two indices became higher under 100 Hz (no flicker perceived with eyes) with 10% duty cycle, while 50% and 90% duty cycle showed no significant difference. These findings indicate that pulsed light will cause a deviation of heart rate and blood pressure from that under stable light.
{"title":"Study of Heart Rate and Blood Pressure Subject to Pulsed LED Lighting","authors":"Luyao Tang, Xiaolin Zhang, Xiaoli Zhou, Xinyuan Gu, Shenglong Fan, Muqing Liu","doi":"10.1080/15502724.2021.1920974","DOIUrl":"https://doi.org/10.1080/15502724.2021.1920974","url":null,"abstract":"ABSTRACT It has been proved that lighting has nonvisual effects on the human body, including changes in heart rate and blood pressure. Heart rate and blood pressure are associated with the autonomic nervous system and can indicate stress level. The present study investigates whether heart rate and blood pressure are influenced by the frequency or duty cycle of pulsed light, together with the duration of lighting. Twelve healthy young subjects were recruited for the investigation. Subjects were exposed to pulsed light of varying frequencies (40 Hz, 100 Hz, 300 Hz) and duty cycles (10%, 50%, 90%). Exposure time was divided into two groups: short-time (20 min) and long-time (3 hours). Heart rate and blood pressure were measured during the experiments. Results showed that after a short lighting period (20 min), heart rate and blood pressure were significantly higher under 40 Hz pulsed than that under stable light, while 100 Hz and 300 Hz had no significant difference. After 3 hours of exposure time, the two indices became higher under 100 Hz (no flicker perceived with eyes) with 10% duty cycle, while 50% and 90% duty cycle showed no significant difference. These findings indicate that pulsed light will cause a deviation of heart rate and blood pressure from that under stable light.","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"7 1","pages":"145 - 153"},"PeriodicalIF":3.6,"publicationDate":"2021-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89987504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-25DOI: 10.1080/15502724.2021.1921593
I. Fryc, S. Bará, M. Aubé, J. Barentine, J. Zamorano
ABSTRACT Due to the typical ambient light levels in inhabited places and light pollution of the night sky, most naked-eye astronomical observations are performed nowadays under mesopic conditions. The luminance (cd/m2) associated with the brightness of the night sky specified in the astronomical logarithmic scale of magnitudes per square arcsecond (mag/arcsec2) is strongly dependent on the spectrum of the sky, because the spectral sensitivity of the human visual system is not coincident with the standard photometric bands used in astronomy. The conversion between these two families of photometric systems was previously analyzed for observers presumed to be either fully photopically or scotopically adapted. In this work, we deduce the transformation equations between the astronomical and visual photometric systems for specifying and reporting the sky brightness in the mesopic range, within the framework of the MES-2 system for visual performance-based mesopic photometry. It is shown that the dependence of the conversion factors on the correlated color temperature of the night sky reaches a minimum spread for adaptation luminances of 0.5–1.0 cd/m2. The sky luminances corresponding to 22.0 mag/arcsec2 in the Johnson-Cousins V band (the assumed brightness of a natural night sky devoid of light pollution) span, for 1.0 cd/m2 adaptation, a relatively small range of ~195–215 μcd/m2 in the absolute (AB) magnitude system and ~210–225 μcd/m2 in the Vega-referenced one.
{"title":"On the Relation between the Astronomical and Visual Photometric Systems in Specifying the Brightness of the Night Sky for Mesopically Adapted Observers","authors":"I. Fryc, S. Bará, M. Aubé, J. Barentine, J. Zamorano","doi":"10.1080/15502724.2021.1921593","DOIUrl":"https://doi.org/10.1080/15502724.2021.1921593","url":null,"abstract":"ABSTRACT Due to the typical ambient light levels in inhabited places and light pollution of the night sky, most naked-eye astronomical observations are performed nowadays under mesopic conditions. The luminance (cd/m2) associated with the brightness of the night sky specified in the astronomical logarithmic scale of magnitudes per square arcsecond (mag/arcsec2) is strongly dependent on the spectrum of the sky, because the spectral sensitivity of the human visual system is not coincident with the standard photometric bands used in astronomy. The conversion between these two families of photometric systems was previously analyzed for observers presumed to be either fully photopically or scotopically adapted. In this work, we deduce the transformation equations between the astronomical and visual photometric systems for specifying and reporting the sky brightness in the mesopic range, within the framework of the MES-2 system for visual performance-based mesopic photometry. It is shown that the dependence of the conversion factors on the correlated color temperature of the night sky reaches a minimum spread for adaptation luminances of 0.5–1.0 cd/m2. The sky luminances corresponding to 22.0 mag/arcsec2 in the Johnson-Cousins V band (the assumed brightness of a natural night sky devoid of light pollution) span, for 1.0 cd/m2 adaptation, a relatively small range of ~195–215 μcd/m2 in the absolute (AB) magnitude system and ~210–225 μcd/m2 in the Vega-referenced one.","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"47 1","pages":"447 - 458"},"PeriodicalIF":3.6,"publicationDate":"2021-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84631573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-19DOI: 10.1080/15502724.2021.1896366
Selcen Akbay Çelikmez, L. Öztürk
ABSTRACT Shadows, modelling, and directional lighting are lighting criteria which are closely related with each other. Shadows have two attributes, namely harshness-softness and lightness-darkness. Both attributes can be examined in two respects that is self-shadow and cast-shadow. A shadow with sharp edges is harsh shadow, while a shadow with blurred edges is soft shadow. The size of the luminaire determines whether the edges of a shadow are sharp or blur. The contrast between the illuminated and the shaded areas determines the lightness-darkness of shadows. If this contrast is weak the shadow is perceived as light, while a strong contrast causes the shadow to be perceived as dark. The observer is often unable to distinguish the effects of two different shadow attributes from each other and judges the appearance of objects or faces as a whole as pleasant or not. However, the two properties of shadows can be defined independently from each other and considered separately as lighting design criteria. Directional lighting is used when the texture and shape of objects or people are to be revealed or emphasized. Finally, it can be said that modelling describes the general appearance of objects and people and involves both the shadow properties and the effects of directional lighting. The aim of this study is to define an index with regard to the lightness-darkness attribute of shadows. The approach developed in this respect is applied for both cast- and self-shadows. The acceptable limits for both indexes are determined based on the main types of luminaires that are often installed in a room. The introduced lightness-darkness indexes with their limit values can be considered as lighting design criteria.
{"title":"An Approach for Determining an Index for Lightness-Darkness Attribute of Shadows in Artificial Lit Spaces","authors":"Selcen Akbay Çelikmez, L. Öztürk","doi":"10.1080/15502724.2021.1896366","DOIUrl":"https://doi.org/10.1080/15502724.2021.1896366","url":null,"abstract":"ABSTRACT Shadows, modelling, and directional lighting are lighting criteria which are closely related with each other. Shadows have two attributes, namely harshness-softness and lightness-darkness. Both attributes can be examined in two respects that is self-shadow and cast-shadow. A shadow with sharp edges is harsh shadow, while a shadow with blurred edges is soft shadow. The size of the luminaire determines whether the edges of a shadow are sharp or blur. The contrast between the illuminated and the shaded areas determines the lightness-darkness of shadows. If this contrast is weak the shadow is perceived as light, while a strong contrast causes the shadow to be perceived as dark. The observer is often unable to distinguish the effects of two different shadow attributes from each other and judges the appearance of objects or faces as a whole as pleasant or not. However, the two properties of shadows can be defined independently from each other and considered separately as lighting design criteria. Directional lighting is used when the texture and shape of objects or people are to be revealed or emphasized. Finally, it can be said that modelling describes the general appearance of objects and people and involves both the shadow properties and the effects of directional lighting. The aim of this study is to define an index with regard to the lightness-darkness attribute of shadows. The approach developed in this respect is applied for both cast- and self-shadows. The acceptable limits for both indexes are determined based on the main types of luminaires that are often installed in a room. The introduced lightness-darkness indexes with their limit values can be considered as lighting design criteria.","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"18 1","pages":"357 - 373"},"PeriodicalIF":3.6,"publicationDate":"2021-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81292745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-08DOI: 10.1080/15502724.2021.1887744
Kaveh Ahmadian Tazehmahaleh, Kevin A. G. Smet, P. Hanselaer
ABSTRACT The availability of quasi-monochromatic Light Emitting Diodes (LEDs) with peak wavelengths distributed over the visible spectrum has opened the way to the development of multichannel LED light sources generating tunable illumination spectra. As the color appearance of an object is strongly influenced by the spectral power distribution of the light source, these multichannel light sources are also commonly used as a research tool in color quality studies. In a number of studies, spectrum optimization algorithms are applied in order to generate a target spectrum directly. Other papers report on the calculation of an illumination spectrum with the aim to optimize one or a set of general quality metrics such as the luminous efficacy of radiation and the color rendering index Ra or Rf. The approach followed in this paper is to explore and visualize, for a given multichannel LED light source, the lighting quality parameters which can be reached within the chromaticity gamut for a selected object. For any predefined target white point chromaticity, the illumination metamers are calculated analytically within the constraints defined by the multichannel LED light source under consideration. The solution space is sampled with a brute force method and the values of any general or specific color quality index can be evaluated. For a predefined object spectral reflectance (or one typical spectral reflectance representative for a set of objects), the object chromaticity gamut is derived. Several object chromaticity targets within the gamut, such as the memory color of familiar objects, can be selected and the impact of “local” variations of the hue and chroma within this gamut on the general and special lighting quality indices and on the user preference can be checked. This can simplify the selection of an object-based optimum illumination spectrum. The approach is illustrated in practice using a five-channel LED light source which was developed in-house.
{"title":"Visualization of Lighting Quality and Object Appearance When Using Multichannel Light Sources","authors":"Kaveh Ahmadian Tazehmahaleh, Kevin A. G. Smet, P. Hanselaer","doi":"10.1080/15502724.2021.1887744","DOIUrl":"https://doi.org/10.1080/15502724.2021.1887744","url":null,"abstract":"ABSTRACT The availability of quasi-monochromatic Light Emitting Diodes (LEDs) with peak wavelengths distributed over the visible spectrum has opened the way to the development of multichannel LED light sources generating tunable illumination spectra. As the color appearance of an object is strongly influenced by the spectral power distribution of the light source, these multichannel light sources are also commonly used as a research tool in color quality studies. In a number of studies, spectrum optimization algorithms are applied in order to generate a target spectrum directly. Other papers report on the calculation of an illumination spectrum with the aim to optimize one or a set of general quality metrics such as the luminous efficacy of radiation and the color rendering index Ra or Rf. The approach followed in this paper is to explore and visualize, for a given multichannel LED light source, the lighting quality parameters which can be reached within the chromaticity gamut for a selected object. For any predefined target white point chromaticity, the illumination metamers are calculated analytically within the constraints defined by the multichannel LED light source under consideration. The solution space is sampled with a brute force method and the values of any general or specific color quality index can be evaluated. For a predefined object spectral reflectance (or one typical spectral reflectance representative for a set of objects), the object chromaticity gamut is derived. Several object chromaticity targets within the gamut, such as the memory color of familiar objects, can be selected and the impact of “local” variations of the hue and chroma within this gamut on the general and special lighting quality indices and on the user preference can be checked. This can simplify the selection of an object-based optimum illumination spectrum. The approach is illustrated in practice using a five-channel LED light source which was developed in-house.","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"12 1","pages":"232 - 245"},"PeriodicalIF":3.6,"publicationDate":"2021-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77321205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-03DOI: 10.1080/15502724.2021.1885271
K. Houser
{"title":"It’s Official, Light is Not Just for Vision","authors":"K. Houser","doi":"10.1080/15502724.2021.1885271","DOIUrl":"https://doi.org/10.1080/15502724.2021.1885271","url":null,"abstract":"","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"30 1","pages":"107 - 107"},"PeriodicalIF":3.6,"publicationDate":"2021-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91275355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-26DOI: 10.1080/15502724.2021.1872383
C. Vetter, P. Pattison, K. Houser, M. Herf, A. Phillips, K. Wright, D. Skene, G. Brainard, D. Boivin, G. Glickman
ABSTRACT Architectural lighting has potent biological effects but applied lighting practices that capitalize on this potential have been limited. In this review, we endeavor to consolidate and synthesize key references that will be useful for lighting professionals, with the goal of supporting knowledge translation into pragmatic lighting strategies. Specifically, we explain relevant terminology, outline basic concepts, identify key references, provide a balanced overview of the current state of knowledge, and highlight important remaining questions. We summarize the physiological effects of light on human health and well-being, including a description of the processes underlying the photic regulation of circadian, neuroendocrine, and neurobehavioral functions. We review seminal work elucidating the elements mediating the potency of light for these physiological responses, with specific attention to factors critical for interpreting those findings. In parallel, we explain and endorse melanopic Equivalent Daylight Illuminance ( ) as the preferred measure to quantify the biological potency of light. Ultimately, while future studies are necessary to further facilitate the translation of laboratory knowledge to domestic and workplace settings, the immediate potential for applied lighting to better support human health is clear. Aiming for integrative lighting solutions that have biologically high potency light during the day and low potency during the night is perhaps the most immediate improvement to be made in order to better support applications for humans.
{"title":"A Review of Human Physiological Responses to Light: Implications for the Development of Integrative Lighting Solutions","authors":"C. Vetter, P. Pattison, K. Houser, M. Herf, A. Phillips, K. Wright, D. Skene, G. Brainard, D. Boivin, G. Glickman","doi":"10.1080/15502724.2021.1872383","DOIUrl":"https://doi.org/10.1080/15502724.2021.1872383","url":null,"abstract":"ABSTRACT Architectural lighting has potent biological effects but applied lighting practices that capitalize on this potential have been limited. In this review, we endeavor to consolidate and synthesize key references that will be useful for lighting professionals, with the goal of supporting knowledge translation into pragmatic lighting strategies. Specifically, we explain relevant terminology, outline basic concepts, identify key references, provide a balanced overview of the current state of knowledge, and highlight important remaining questions. We summarize the physiological effects of light on human health and well-being, including a description of the processes underlying the photic regulation of circadian, neuroendocrine, and neurobehavioral functions. We review seminal work elucidating the elements mediating the potency of light for these physiological responses, with specific attention to factors critical for interpreting those findings. In parallel, we explain and endorse melanopic Equivalent Daylight Illuminance ( ) as the preferred measure to quantify the biological potency of light. Ultimately, while future studies are necessary to further facilitate the translation of laboratory knowledge to domestic and workplace settings, the immediate potential for applied lighting to better support human health is clear. Aiming for integrative lighting solutions that have biologically high potency light during the day and low potency during the night is perhaps the most immediate improvement to be made in order to better support applications for humans.","PeriodicalId":49911,"journal":{"name":"Leukos","volume":"78 2 1","pages":"387 - 414"},"PeriodicalIF":3.6,"publicationDate":"2021-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76967698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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