Total Daylight Research Articles

Longer days, larger grays: carryover effects of photoperiod and temperature in gray treefrogs, Hyla versicolor.

Environmental conditions like temperature and photoperiod can strongly shape organisms' growth and development. For many ectotherms with complex life cycles, global change will cause their offspring to experience warmer conditions and earlier-season photoperiods, two variables that can induce conflicting responses. We experimentally manipulated photoperiod and temperature during gray treefrog (Hyla versicolor) larval development to examine effects at metamorphosis and during short (10-day) and long (56-day) periods post-metamorphosis. Both early- and late-season photoperiods (April and August) decreased age and size at metamorphosis relative to the average-season (June) photoperiod, while warmer temperatures decreased age but increased size at metamorphosis. Warmer larval temperatures reduced short-term juvenile growth but had no long-term effect. Conversely, photoperiod had no short-term carryover effect, but juveniles from early- and late-season larval photoperiods had lower long-term growth rates than juveniles from the average-season photoperiod. Similar responses to early- and late-season photoperiods may be due to reduced total daylight compared with average-season photoperiods. However, juveniles from late-season photoperiods selected cooler temperatures than early-season juveniles, suggesting that not all effects of photoperiod were due to total light exposure. Our results indicate that despite both temperature and photoperiod affecting metamorphosis, the long-term effects of photoperiod may be much stronger than those of temperature.

Improved Land Use Efficiency Through Spectral Beam Splitting in Agrivoltaic Farms

Installing photovoltaic (PV) collectors above arable land (Agrivoltaics) can aid with the shortage of available land area for solar power generation and food production. Most open field agrivoltaics are based on opaque PV devices which absorb photosynthetically active radiation (PAR, 400-700 nm), reducing crop yield and increasing variability in light distribution across the field. This research evaluates the performance of spectral beam splitter integrated photovoltaic (BSIPV) modules using a PV performance model. A high percentage (66 %) of PAR incident on the spectral beam splitter is transmitted effectively to the plants, while the near infrared radiation (NIR, > 700 nm) is reflected to the adjacent bifacial opaque photovoltaic module to generate power. In the model, seven rows of modules were placed uniformly across the field at a height of four meters from the ground. Considering a cool season (November – March) in Yuma, Arizona, in a conventional opaque PV agrivoltaic farm received 43 % lower total daylight integral (TDLI) across the season in comparison to open field with a coefficient of variation (ratio of standard deviation to mean expressed in percentage) of 56 % in TDLI across the field. On the other hand, the BSIPV agrivoltaic farm limited the drop in TDLI to 7 % in comparison to open field and the coefficient of variation to 14 % across the field. Thus, BSIPV showed a 36 % improvement in TDLI relative to the conventional opaque PV agrivoltaic farm. The results of the current study justify further research on the proposed collector concept.

0243 SLEEP REGULARITY AND MENTAL HEALTH DURING EXTENDED ANTARCTIC RESIDENCE

Abstract Introduction As humans’ advance towards a Mars mission, ensuring astronaut safety, well-being, and performance becomes increasingly critical. Long-duration space exploration presents several challenges for human sleep, including altered photoperiods, prolonged confinement, and monotony. Antarctica provides an ideal analog for understanding how these and other stressors impact sleep over time. Prior studies among Antarctic cohorts have found reduced total sleep, increased sleep onset, and circadian phase delay. However, day-to-day regularity of sleep-wake patterns in the Antarctic over prolonged periods has not been studied. Methods Crew members (N= 110) at a coastal (McMurdo: MM, n = 88) and an inland Antarctic station (South Pole: SP, n = 22) were studied longitudinally for up to 9-months. Sleep was monitored continuously with actigraphy (Actiwatch Spectrum, Philips Respironics) and examined in relation to cumulative time on station and calendar month (photoperiod). Self-reported mental health symptoms were also examined monthly using The Mental Health Checklist (MHCL). The Sleep Regularity Index (SRI; Phillips et al., 2017) which calculates the percentage probability of an individual being in the same state (sleep vs. wake) at any two time-points 24 hours apart was calculated to examine sleep regularity over time. Results Controlling for time on station prior to participation, we observed no significant changes in monthly SRI over a 6-month period at MM where photoperiod alterations are less extreme. At SP, SRI remained very stable during months of total daylight but declined during winter months in the absence of sunlight. SRI scores were significantly different between month-8 and month-9 and with large effect sizes across month-7, month-8, and month-9. Participants with lower month-7 SRI scores had significantly higher MHCL poor self-regulation scores at the end of the mission. Conclusion Day-to-day variability in sleep–wake patterns is an important predictor of health and safety. Our findings show reductions in sleep regularity during prolonged Antarctic residence particularly at the SP station, where sunlight is absent for 6 months of the year. Less sleep regularity predicted worse mental health functioning. These findings suggest that mitigation the impact of altered light-dark cycles on sleep is critical for a Mars mission. Support (if any) NASA award #NNX15AC13G S014 to the last author.

Estimation of daylight availability in Kolkata and approximation of indoor daylight levels for different daylighting methods

ABSTRACT This work estimated the daylight availability and luminous efficacy of solar illuminance and approximated indoor daylight levels for various indoor daylighting methods for Kolkata, a major city in eastern India having tropical savanna climate, by applying two computational methods: the Perez model and the IESNA recommended calculation procedure. It was found that hourly horizontal diffuse and global illuminance, horizontal sky and total daylight illuminance values remained mostly over 10 klx throughout the year, and global and diffuse luminous efficacies mostly remained around 95–120 and 110–150 lm/W, respectively. The linear correlation between solar irradiation and estimated illuminance was stronger for Perez model. Thus, the application of Perez model was considered the better choice to appraise the daylighting potential of Kolkata.

Evaluation of the Environmental Bias on Accelerometer-Measured Total Daily Activity Counts and Owner Survey Responses in Dogs with Osteoarthritis.

Objective To determine if environmental variables affect the average daily activity counts (AC) of dogs with osteoarthritis (OA) and/or owners' perception of their dog's clinical signs or quality of life. Methods The AC and Canine Brief Pain Inventory (CBPI) owner questionnaires of 62 dogs with OA were compared with daily environmental variables including the following: average temperature (°C), high temperature (°C), low temperature (°C), relative humidity (%), total precipitation (mm), average barometric pressure (hPa) and total daylight hours. Results Daily AC significantly correlated with average temperature and total daylight hours, but average temperature and total daylight hours accounted for less than 1% of variation in AC. No other significant relationships were found between daily AC and daily high temperature, low temperature, relative humidity, total precipitation or average barometric pressure. No statistical relationship was found between daily AC and the CBPI, nor between environmental variables and the CBPI. Canine Brief Pain Inventory scores for pain severity and pain interference decreased significantly over the test period. Clinical Significance The relationship between daily AC and average temperature and total daylight hours was significant, but unlikely to be clinically significant. Thus, environmental variables do not appear to have a clinically relevant bias on AC or owner CBPI questionnaires. The decrease over time in CBPI pain severity and pain interference values suggests owners completing the CBPI in this study were influenced by a caregiver placebo effect.

Daylight evaluation for educational facilities established in high-rise housing complexes in Daegu, South Korea

This study conducted a daylight evaluation of schools established in high-rise housing complexes in a Korean city. This was accomplished through a daylight simulation test and a questionnaire survey on students' perception of and satisfaction with daylight in their classrooms. The simulation test showed that the amount of daylight to which a school was exposed could be affected by the surrounding high-rise housing complex, and that the distance between the complex and the school had an influence on the amount of daylight seen in classrooms. When the total daylight hours numbered less than four, or when the number of continuous daylight hours was less than two, students' satisfaction with daylight was low. According to survey results, most students felt that daylight had an influence on their educational environment and learning performance. It is therefore deemed necessary to fully consider the surroundings when designing education facilities.

Activity time budget patterns of sheep and goats co-grazing on semi-natural species-rich dry grassland

Activity time budget patterns and grazing response to sward and environmental conditions were investigated for paddocks of sheep and goats co-grazing for conservation purposes on a semi-natural species-rich dry grassland community endangered by shrub and tall perennial plant encroachment in a protected nature reserve in South Moravia (Czech Republic). Grazing was conducted by a rotational stocking system for 14 weeks in late grazing season in 2008 with 60 dry ewes and 20 goats. Twelve ewes and four goats were observed; grazing, ruminating, idling and other activities (salt licking, social interactions, walking), along with topographical position in the paddock were recorded at 5-minute intervals within 14 hours of daylight. Sheep and goats did not differ in their principal activity time budgets, such as the average total daylight time spent grazing (sheep: 8.57 h, goats: 8.59 h), ruminating (sheep: 1.42 h, goats: 1.44 h), or idling (sheep: 3.23 h, goats: 3.18 h), the duration of bouts of each activity, or the number of bouts of grazing and ruminating. There was no pattern in activity time budgets indicating dynamics in progressing season, nor was there a response to daily average temperature or to paddock size. Sheep and goats showed similar responses to groundcover of particular plant functional types. The animals showed a positive trend in response of total daylight grazing time to grass available biomass and a negative response of total daylight grazing time to herbaceous biomass for both sheep and goats. The total daylight grazing time was independent of availability of woody plants. Goats devoted more time (1.51 h) to other activities than sheep (1.34 h), especially to social interactions and salt licking. On the other hand, sheep spent proportionally more time walking. Both sheep and goats showed similar patterns in spatial use of paddocks on hill slopes, spending the most time in the middle part and the least time in the lower part of paddocks. 

Timing of herbage allocation in strip grazing: Effects on grazing pattern and performance of beef heifers1

The timing of grazing bouts (GB) determines how cattle allot time to meet their nutritional needs. Net photosynthesis and evapotranspirational losses increase herbage nonstructural carbohydrate and DM concentrations, which may lead to longer and more intense GB at dusk. Hence, linking the grazing pattern, plant phenology, and herbage allocation time emerges as an option to manipulate the GB and nutrient intake. The objectives of this work were to analyze grazing behavior and performance of beef heifers when herbage allocation was at 0700 each morning (MHA) or at 1500 each afternoon (AHA). Two pairs of experiments were conducted during the winter and spring examining behavior and performance. Measurements were grazing, rumination, and idling times during daylight hours, and their patterns, as well as bite rate, ADG, change in BCS, and daily herbage DMI. In the behavioral experiments, 8 heifers strip-grazed annual ryegrass (Lolium multiflorum Lam.). The grazing, rumination, and idling times as well as bite rate were measured and also analyzed per time of day. In the performance experiments, 48 beef heifers strip-grazed annual ryegrass in 2 groups according to treatments. Daily DMI, ADG, and changes in BCS were analyzed. The AHA increased daily idling time (P < 0.01) and decreased grazing time (P < 0.01). The AHA concentrated grazing time in the evening, when bite rate was greater (P < 0.01). The daylight rumination time varied by time of day (P < 0.01), but total daylight rumination time did not differ (P = 0.11). With AHA, rumination time and idling time were concentrated in the morning and afternoon. In the performance experiment during the winter, there was a treatment x week effect (P < 0.01) for ADG and change in BCS. Beginning in wk 4, heifers in AHA gained 150 g of BW and 0.0145 points of BCS more than those in MHA (P < 0.05) per day. In the spring, AHA increased ADG by 549 g and 0.0145 points of BCS more than those in MHA (P < 0.05) per day during the entire 6 wk. The herbage DMI (kg/d) did not differ in winter (AHA, 5.0 vs. MHA, 4.5) or spring (AHA, 5.6 vs. MHA, 5.0). These results suggest that timing of herbage allocation alters grazing, rumination, and idling patterns; AHA leads to longer and more intense GB when herbage has greater quality, which improves cattle performance.

Evaluating the potential for energy savings on lighting by integrating fibre optics in buildings

The effective integration of an artificial lighting system and daylight in buildings occurs only when the artificial lighting system can be switched on or off as a function of daylight levels reaching the working surface of spaces. The paper considers fibre optics technology as a means of supplementing the daylight received at the rear of rooms and the subsequent integration of the total daylight received with a controlled artificial lighting system. Such an approach would contribute not only to energy savings but also to a reduction in environmental pollution. The evaluation took place using the climatic data from seven cities in Brazil and one in the UK. Results showed that by effectively integrating daylight from windows in buildings with the artificial lighting system, energy savings ranging from 17.7% to 92.0% could be achieved in the seven cities in Brazil and savings ranging from 10.8% to 44.0% could be achieved in the UK. By incorporating fibre optic technology into the system, the potential for energy savings on lighting was then found to range from 8.0% to 82.3% for the cities in Brazil and from 56.0% to 89.2% in the UK. For the city in the UK, it was further shown that there would be a reduction in carbon dioxide emission of 122 kg/m 2 of built area per year if daylight from windows were integrated with the artificial lighting system, and that this would increase to 138 kg/m 2 per year if fibre optics technology were to be installed.

Feeding of diving predators and diel vertical migration of prey: King penguin diet versus trawl sampling at Kerguelen Islands

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 227:51-61 (2002) - doi:10.3354/meps227051 Feeding of diving predators and diel vertical migration of prey: King penguins¹ diet versus trawl sampling at Kerguelen Islands C. A. Bost1,*, T. Zorn1, Y. Le Maho1, G. Duhamel2 1Centre d¹Ecologie et Physiologie Energétiques, 23 rue Becquerel, 67087 Strasbourg Cedex 2, France 2Muséum National d¹Histoire Naturelle, Laboratoire d¹Ichtyologie Générale et Appliquée, 43 rue Cuvier, 75231 Paris Cedex 05, France *E-mail: charles.bost@c-strasbourg.fr ABSTRACT: The diving behavior and diet composition of King penguins were examined during summer 1995 at Kerguelen Islands. This was in relation to real-time estimations of diel prey availability during 2 sampling sessions totaling 10 d at sea. During daylight hours King penguins performed medium to deep dives of 120-250 m. At night, they dived no deeper than 60 m. Daytime, dusk and night-time sampling of prey was performed in the depth ranges corresponding to the depths of the penguins¹ dives in this study. The diversity in mesopelagic fish was found to be highest during the night at 0-50 m (15 vs 9 species during the day), and their number was up to 20-fold higher at these depths at night than during the day at the 150-250 m depth layer. The 3 myctophid species Electrona antarctica, Gymnoscopelus fraseri and G. braueri which were present in large sub-surface numbers during the night were virtually absent from the penguins¹ diet. The 2 species dominant in their diet, Muraenolepis marmoratus and Krefftichtys anderssoni (56.5 and 32.9% by number, 30.3 and 31.6% by biomass, respectively), were scarcely detected in the penguins¹ diving range during the night. In contrast, these 2 species, of which only the latter is bioluminescent, were significantly present during the day in the 0-300 m depth range (16.5 and 30.0% of the diurnal catches by number, respectively). In terms of biomass, these 2 prey types constituted only 6.3 and 12.6% of the total daylight trawls, which were dominated by the genus Protomyctophym (38.6% of the catches). The overlap between the penguins¹ diet and trawl content was the most significant with daylight sampled data. King penguin feeding success seems mostly dependent on deep dives during the day, despite lower prey availability than during the night. Ambient light levels, which were found to be higher at deeper depths (150-180 m) during the day compared to the sub-surface (0-60 m) at night-time, therefore appear to better determine King penguin foraging success than diel migration of prey to shallow depths. KEY WORDS: King penguins · Diet · Diel vertical migration · Myctophids · Foraging behavior Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 227. Online publication date: February 13, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

UV doses of Americans.

The UV doses of Americans were never measured, but are needed for assessing the risks of UV-related health effects. We calculated these doses using a novel approach. The Environmental Protection Agency's (EPA) National Human Activity Pattern Survey (NHAPS) recorded the activity profiles of 9386 Americans over 24 months to assess their exposure to environmental pollutants, one of which is UV radiation. NHAPS used randomized telephone interviews to get their previous day's minute-by-minute activities. From NHAPS we extracted only the outdoor-daylight data of the northern and southern indoor workers (95%), stratifying by season, sex and age (0-21, 22-40, 41-59 and 60+ years) to find the average time Americans spend outdoors. Knowing the total daylight time and that while outdoors Americans are exposed to about 30% of the available solar UV (on a horizontal plane), we calculated their percent ambients. The average American's percent ambients are 2.6 and 2.5% for northern and southern females, respectively, and 3.5 and 3.6% for northern and southern males, respectively. Men over 40 years of age have the highest ambients (4%). From their ambients we calculated their annual doses using seasonal averages of UV measurements taken daily for over 2 years by EPA Brewer spectrophotometers located in four quadrants of the United States: Atlanta, GA; Boston, MA; Bozeman, MT and Riverside, CA. The average erythemal UV doses of Americans are about 25,000 J/m2/year, 22,000 for females and 28,000 for males, or 33,000 J/m2/year including a conservative continental U.S. vacation (7800 J/m2). Thus, we can now assess the risks of UV-related health effects for Americans.

Effects of poults on plasma concentrations of prolactin in turkey hens incubating without eggs or a nest.

1. Plasma prolactin (PRL) concentrations, total daylight sitting time and extent of brood patch development were compared in singly caged hens incubating without a nest or eggs and in penned hens incubating eggs in nest boxes. No significant differences were found in any of the three measures of incubation intensity. 2. When 10 newly-hatched poults were placed in the cages of incubating hens their plasma PRL concentrations fell rapidly. No fall in plasma PRL was observed in hens that could see and hear, but not touch the poults. 3. When physical contact between hens and poults was maintained, visual isolation of hens from poults, surgical devocalisation of poults, or the combination of visual isolation and devocalisation of poults had no effect on the poult-stimulated decline in plasma PRL concentrations. 4. Sensory cues from poults that evoke the PRL response in incubating hens are primarily tactile.

Spawning Periodicity of the Asiatic Clam Corbicula fluminea in the New River, Virginia

Spawning periodicity of the Asiatic clam Corbiculafluminea in the New River, Virginia, is reported. Numbers of newly recruited larvae in the New River sediment, number and life stage of larvae naturally released and collected from adults held in the laboratory, and presence of developing veligers within the brood chambers of sacrificed adults were collected weekly from May to December 1984. Abiotic data collected consist of mean weekly water temperatures, daily total daylight hours for the western Virginia vicinity and mean daily discharge rates. Density of larvae in sediment, total numbers of larvae collected from laboratoryheld adults, and brood chamber condition are all highly similar in timing, duration and intensity of spawning effort. There were three major peaks in larval abundance-late spring, midsummer and early autumn. These observations do not coincide with previously reported patterns of spring and autumn reproductive peaks by Corbiculafluminea. INTRODUCTION Since the introduction of Corbicula fluminea to the Pacific northwest coast of North America in the 1930s, the Asiatic clam has spread S and E. Its northerly migration has been limited only by winter extremes in water temperature (McMahon, 1982). Initial reports of C. fluminea in Virginia placed this species in the James River (Diaz, 1974) and the New River (Rodgers et al., 1977). Colonization of available habitats by this organism has not been limited to natural waterways but includes the establishment of viable populations in utility and industrial cooling water systems (Morton, 1979; Cherry et al., 1980). The impact of these incursions into environmental and industrial facilities has produced both ecological and economic repercussions of significant proportions that are reviewed in detail elsewhere (Ingram, 1959; Sinclair and Isom, 1963; Fuller and Imlay, 1976; Gardner et al., 1976; Fuller and Richardson, 1977; Goss and Cain, 1977; McMahon, 1977; Boozer and Mirkes, 1979; Kraemer, 1979; Smith et al., 1979; Harvey, 1981). One attribute that apparently facilitates rapid colonization is the reproductive capacity of this species. Kraemer and Lott (1977) reported that Corbicula sp. is hermaphroditic, possessing both oogenic and spermatogenic tissue. While the male and female gametes are formed in different parts of the gonads, they seem to be shed through the same ducts. This prompted the speculation that individuals may possess the ability for internal self-fertilization. Britton and Morton (1982) suggested that cross-fertilizing individuals achieve fertilization in the maternal suprabranchial chamber after spermatozoa have entered the infrabranchial chamber through the incurrent siphon. Once fertilized, eggs are either retained and incubated within the inner demibranch (gill) or discharged as conglutinates of eggs, the mode being species-specific (Sinclair and Isom, 1963). Incubatory species retain the developing embryos through the trochophore and early veliger stages prior to being expelled through the exhalant siphon as pediveligers. This study summarizes our efforts in documenting the reproductive activities of Corbicula fluminea in the New River, Virginia, during 1984. Three different approaches 'Send correspondence to F. G. Doherty. Present address: Joint Graduate Program in Toxicology. College of Pharmacy, Busch Campus, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854.

Photoperiodic mechanisms and rhythms of reproduction in the female rainbow trout

The present work investigates the importance of circadian and circannual rhythms in the photoperiodic control of reproduction in the rainbow trout. Maintenance of groups of 20-30 female trout under continuous light (LL), constant long (18L:6D) or short (6L:18D) days and conditions of constant temperature (8.5-9.0°C) and feeding rates (0.5% body weight, day(-1)), starting in February, produced markedly different spawning periodicities during the first and subsequent years of treatment. At the end of the first year, spawning was advanced by up to 2 months in the fish under LL and 18L:6D and delayed by up to 5 months in those under 6L:18D when compared with the December spawning of control fish under ambient light. Continued exposure of the fish to the same photoperiod regimes produced cycles of spawning and peak levels of testosterone, oestradiol-17β and calcium (as an index of vitellogenin) at intervals of 150-170 days under LL and 18L:6D and 320-420 days under 6L:18D. The functional importance of these spawning cycles and their relationship to circannual rhythms and the control of reproduction is discussed.Exposure of fish to skeleton (6L:4D:2L:12D, 6L:6D:2L:10D and 6L:8D:2L:8D) and resonance (6L:42D, 6L:48D and 6L:54D) procedures produced ranges of spawning times up to two months in advance of control fish. Results with the resonance regimes, where fish received only a half the light-dark cycles and a quarter of the total daylight hours of those on ambient light cycles show that trout do not measure daylength and time by counting daily cycles or by hour-glass mechanisms. Collectively, these data support the proposition that rhythmic processes of photosensitivity are involved in the modulation of reproductive development in the rainbow trout and that circadian and circannual rhythms cooperate in the timing and entrainment of this cycle.

Cattle Use of Riparian Meadows in the Blue Mountains of Northeastern Oregon

Cattle Use of Riparian Meadows in the Blue Mountains of Northeastern Oregon

The Satellite Radiology Department With A Total Daylight Loading System

The Satellite Radiology Department With A Total Daylight Loading System

Spectral irradiance of daylight at Pretoria

Average spectral irradiance values are given for total daylight, skylight and south sky irradiances as measured during seven months at Pretoria. Special attention is given to values for air mass 1 to enable comparison with data obtained elsewhere. Some results are also given showing the attenuation of daylight irradiance due to smoke and other pollutants.

Impact of Daylight Exposure on Sleep Time and Quality of Elementary School Children

The purpose of this study was to examine how daylight exposure affects the health and well-being of elementary school children. Sleep actigraphy data were the main dependent variables in this study. Independent variables were total light and daylight levels elementary school children were exposed to inside their classrooms as well as outside. Participants were composed of elementary school children (46% female, mean age = 7.27 years, ~33% African American) attending a rural and urban schools in the mid-west, each set of children divided into groups according to classroom orientation. Eighty participants in total wore light-sensor equipped actiwatches for one-week to measure sleep quality and exposure to ambient light levels. To assess light levels students were exposed to beyond the one-week of actigraphy measurements, data logging light meters were placed in various locations within the classrooms for an entire semester. Our results seem to indicate that studying in daylit classroom spaces would lead to higher sleep time and quality compared to those who receive little or no daylight. We measured differences as large as 36 minutes. We recommend, therefore, that classroom design need to pay attention to the daily daylight exposures elementary school children are receiving.

Spectroradiometric and Colorimetric Characteristics of Daylight in the Southern Hemisphere: Pretoria, South Africa

A description is given of the apparatus and method used to measure the spectral characteristics of daylight between 285 and 775 mμ. These measurements, extending over approximately seven months, were made at Pretoria on total daylight, skylight without sun, and south sky. Spectral energy distributions, CIE chromaticity coordinates, correlated color temperatures, and illuminance values were calculated. The total of 422 sets of spectral energy distributions were averaged into a number of different groups. The derived chromaticities were found to be much closer to the full radiator locus than those previously published, which had been obtained in the northern hemisphere. The ultraviolet content also proved to be relatively high.

The Problem of Illumination in Colour Matching

The factors which govern the suitability of any light source, including the various phases of daylight, for colour matching are discussed from a theoretical standpoint and a review is made of the experimental data available. It is concluded that colour‐matching lamps should be standardised to reproduce the spectral quality of total daylight (colour temperature about 6250K) rather than north‐sky daylight (about 7400K). Spectral‐distribution curves of total daylight are critically reviewed to determine their suitability for this purpose. If, however, it is ultimately decided that colour‐matching lamps should imitate north‐sky daylight, the phase of daylight actually used by professional colour matchers, then Illuminant C is no longer suitable as the standard source for colour matching: lamps emitting light similar in spectral distribution to the Abbot–Gibson 7400K curve, extended to 300 mμ, would be expected to be suitable. The relevant topic of variation in colour vision is discussed and a review is made of commercial colour‐matching lamps.