Top Lighting Research Articles

Interlighting improves production of year-round cucumber

Three cucumber stands ( Cucumis sativus L. cv. Cumuli) were grown in southern Finland to investigate the effects of two supplemental lighting regimes on yield and efficiency of electricity consumption in lighting for year-round production. The lighting regimes examined included top lighting (TL), where all of the lamps were mounted above the canopy and top + interlighting (T + IL) which comprised 75% of top lamps and 25% of the lamps mounted vertically 1.3 m above the ground between the single plant rows. The artificial photosynthetic photon flux (PPF) near the plant rows, the air temperature and vapour pressure deficit (VPD) in the canopy were noted to be slightly higher in T + IL than in TL. The total (natural + artificial) PPF inside the greenhouse during cultivation of the winter, spring and summer stands were 19.4, 29.5 and 38.6 mol m −2 day −1 in TL and 20.4, 31.5 and 41.2 mol m −2 day −1 in T + IL, respectively. Top + interlighting was shown to enhance cucumber productivity; T + IL increased the annual total and first class fruit weight and number, fruit size and percentage of first class fruit. A total annual increase of 20% in first class fruit weight was achieved through a 6% increase in electricity consumption for lighting purposes. The first class fruit weights in winter, spring and summer stands were 32.0, 42.1 and 30.8 kg m −2 in TL and 38.2, 55.4 and 32.1 kg m −2 in T + IL, respectively. The efficiency of electricity consumption for lighting was better for the whole year in T + IL than in TL (120 g versus 108 g first class fruit weight kWh -1). Efficiency varied between stands; T + IL proved more efficient than TL during the winter and spring seasons, whereas TL was more efficient in summer.

A methodology for investigating the effect of a south oriented surface on natural illuminance received on north oriented glazing of a top lighting system under clear sky conditions

A methodology for investigating the effect of a south oriented surface with varying inclination angle in reflecting natural light towards a north oriented glazing of a top lighting system is proposed for use under clear sky conditions. This was done based on mathematical simulation for a top lighting system. Results have shown the importance of the reflective surface in increasing the illuminance received on the glazing of the top lighting system.

Evaluation of Seedling Size Following Germination Using Computer-aided Analysis of Digital Images from a Flat-bed Scanner

Early seedling growth rate can be used to estimate seed vigor for small-seeded vegetable and flower seeds. However, hand measurement of small seedlings is tedious and difficult to reproduce among analysts. Computer-aided analysis digital images of seedlings should improve accuracy and reproducibility. A flat-bed scanner fitted with base and top lighting provided high resolution images of even small-seeded species like petunia [Petunia ×hybrida `Blue Picotee' (Hort) Vilm.] and lisianthus [Eustoma grandiflorum `Mariachi Pure White' (Raf.) Shinn]. Uniform lighting was provided and images were captured and analyzed in less than 2 minutes. A clear, cellulose film was used as the germination substrate in petri dish germination assays to facilitate capturing images with a flat-bed scanner. The transparent medium permitted seedlings to be imaged without removal from the petri dish and also allowed for repeated measures of the same seedlings in order to calculate growth rate. Six species evaluated in this study included cauliflower (Brassica oleracea L., var. Botrytis), tomato (Lycopersicon esculentum Mill. `New Yorker'), pepper (Capsicum annuum L. `North Star'), impatiens [Impatiens walleriana Hook. f. `Impact Lavender'], vinca [Catharanthus roseus (L.) G. Don. `Little Bright Eye'], and marigold (Tagetes patula L. `Little Devil Flame'). For germination and early seedling growth, the cellulose film compared favorably with other standard germination media (blue blotter and germination paper) for five of the six species tested. Computer analysis of seedling length was possible for all six species and was statistically similar to hand measurements averaged for three analysts.

Lighting direction affects recognition of untextured faces in photographic positive and negative

Face recognition in photographic positive and negative was examined in a same/different matching task in five lighting direction conditions using untextured 3-D laser-scanned faces. The lighting directions were +60, +30, 0, −30 and −60°, where negative values represent bottom lighting and positive values represent top lighting. Recognition performance was better for faces in positive than in negative when lighting directions were at +60°. In one experiment, the same effect was also found at +30°. However, faces in negative were recognized better than positive when the direction was −60°. There was no difference in recognition performance when the lighting direction was 0 and −30°. These results confirm that the effect of lighting direction can be a determinant of the photographic negative effect. Positive faces, which normally appear to be top-lit, may be difficult to recognize in negative partly because of the accompanying change in apparent lighting direction to bottom-lit.

Effects of lighting on the perception of facial surfaces.

A series of experiments is reported that investigated the effects of variations in lighting and viewpoint on the recognition and matching of facial surfaces. In matching tasks, changing lighting reduced performance, as did changing view, but changing both did not further reduce performance. There were also differences between top and bottom lighting. Recognizing familiar surfaces and matching across changes in viewpoint were more accurate when lighting was from above than when it was from below the heads, and matching between different directions of top lighting was more accurate than between different directions of bottom lighting. Top lighting also benefited matching between views of unfamiliar objects (amoebae), though this benefit was not found for inverted faces. The results are difficult to explain if edge- or image-based representations mediate face processing and seem more consistent with an account in which lighting from above helps the derivation of 3-dimensional shape.

DAYLIGHT CONTROL FOR THE NEW LANTERNS IN THE NORTH GALLERY OF PETWORTH HOUSE, WEST SUSSEX

DAYLIGHT CONTROL FOR THE NEW LANTERNS IN THE NORTH GALLERY OF PETWORTH HOUSE, WEST SUSSEX

Independent effects of lighting, orientation, and stereopsis on the hollow-face illusion.

Three experiments were conducted to investigate factors contributing to the 'hollow face' illusion. A novel method was employed in which the distance from the mask at which the illusion became apparent or disappeared, when retreating or approaching, respectively, was taken as a measure of the strength of the illusion. In all the experiments an effect of direction of observer's movement was found, demonstrating the stability of the initial percept. Upright orientations were compared with inverted ones to investigate if the illusion reflects a bias towards a familiar percept. The direction of lighting was also varied. Independent main effects of orientation and lighting were found to be consistent with preferences both for upright faces and for top lighting. However, inverted faces also produced the illusion to some extent, suggesting a general preference for convexity. The role of stereopsis in resolving the illusion was tested by comparing monocular with binocular viewing conditions. Monocular viewing conditions gave rise to shorter distances, suggesting that the retinal disparities available with binocular viewing are important in disambiguating the illusion at small distances. The results are interpreted within the framework of a 2 1/2-dimensional sketch derived from independent modular processing of visual information.

Artificial Lighting and Spacing as Photosynthetic and Yield Factors in Winter Greenhouse Tomato Culture1

Abstract Photosynthetic and yield responses of tomato, Lycopersicon esculentum L., ev. Tuckcross V and Tuckcross 533 supplemental lighting and spacing were studied during the unusually dark winter of 1972–73. Supplemental lighting and wide spacing increased total flowers, % fruit set, fruit size, and total fruits/plant. and contributed to greater early and total fruit yields. The increases were related to increased apparent photosynthetic rate and efficiency. Supplementary top lighting (184 W/m2) increased fruit weight/plant 1107 g/plant (89%) over natural lighting for an increase of 6.0 g/plant for each watt/m2. Supplementary top + side lighting (368 W/m2) increased fruit weight 2853 g/plant (121%), an increase of 7.7 g/plant for each watt/m2. Maximum fruit yield/plant was obtained with top + side lighting at a spacing of 50.8 × 41 cm in a staggered double row bed. Plant spacing of 38.1 × 41 cm with maximum lighting gave greatest yield/unit area. Photosaturation was not attained bv supplementary lighting.

Physical Observations relating to the 2 MeV Van de Graaff Electrostatic Generator at Westminster Hospital

Miller (1950) has described the 2 MeV Van de Graaff generator installed at Sheffield and some of the physical measurements and observations made with it. A similar apparatus has been installed at Westminster Hospital. This installation and our initial experiences with it have been some what different from those of Miller. Our measurements confirm, and in some cases extend, those of previous workers. The generator was installed within an existing Radiotherapy Department with little disturbance to its routine work, a room previously used for a 200 kV X-ray set being extended and modified. Its position relative to another 200 kV set, control rooms and corridors forming part of the Department is shown in Fig. 1. These rooms form part of a lower ground floor extending well beyond the main building and have top lighting. The roof is normally unoccupied, as is a basement underneath. The area directly beneath the generator is, nevertheless, fenced off. Thus there is no problem of protection above or beneath the a...

Sunlight and Skylight as Determinants of Photographic Exposure II Scene Structure, Directional Index, Photographic Efficiency of Daylight, Safety Factors, and Evaluation of Camera Exposure

Following a brief review of Part I of this communication, additional factors involved in the computation of correct camera exposure are discussed. The first of these is the structure of the scene. Two aspects of structure, namely, spatial structure and local illumination conditions, are recognized. Four categories of spatial structure, definable, at least in a qualitative manner, in terms of distance between scene elements and camera, are described and illustrated pictorially. Local illumination conditions are defined in terms of the extent of shading and four definitely recognizable aspects are described.The minimum scene luminance, Bo min., is determined to a considerable extent by aspects of scene structure, and quantitative values corresponding to combinations of structural elements are given.When an appreciable part of the light entering the scene space comes from a source which subtends a small solid angle, the minimum scene luminance is dependent to some extent upon the direction, relative to the optical axis of the camera system, from which this unidirectional illumination enters the scene space. The angular relationships between this component of the incident light and the optical axis of the camera which results in conditions defined as front lighting, side and top lighting, and back lighting are defined and relative values of Bo min. are given corresponding to these three directional lighting conditions.The speed of photographic negative materials is defined in terms of radiant energy having a specified spectral composition which has been standardized by international agreement. The spectral composition of the radiant energy which, on the average, is reflected from the scene elements of minimum luminance is not identical to that used in the measurement of speed. It is therefore necessary to include a term in the formula for the computation of correct camera exposure, the magnitude of which depends upon the difference in the spectral qualities of the two radiant energies. This factor is expressed in terms of the photographic efficiency of the radiant energy reflected on the average from the scene elements of minimum luminance. This efficiency can be computed, if certain functional relations are known, or it may be measured by methods of photographic photometry. Evidence shows that the values obtained by the two methods are in fairly good agreement. However, it seems advisable to use a value derived by the direct methods of photographic photometry. In this connection the spectral composition of radiant energy in sunlight and skylight is considered in detail. The use of the term color temperature as a significant specification for the spectral composition of radiant energy emitted by natural and artificial sources is examined critically and the conclusion is reached that in the majority of cases a color temperature specification is not adequate for defining the quality, i.e., spectral composition, from the standpoint of photographic efficiency.As a final step in the derivation of the formula for correct camera exposure, certain safety factors are considered and recommended. Up to this point the treatment has been analytical, involving the consideration of many factors. To make the information of practical use, the treatment must be integrated and simplified in such a way that values of correct camera exposure can be determined simply and expeditiously. Three possible methods are discussed for this purpose: a purely arithmetic, a purely logarithmic, and a combination of arithmetic, logarithmic, and simple slide rule operation. The last of these possible techniques turns out to be the simplest and probably the most easily applied in practical work.

Reflection from Glazed Pictures

IN directing attention to the question of avoiding reflection from glazed pictures, Mr. Robert Howden has rendered a useful service both to artists and the public. His paper, read before the Royal Society of Arts on Oct. 3, clearly stated the elements and difficulties of the problem, and it is significant that Sir Edwin Lutyens was in the chair. Mr. Howden recommends replacing the usual flat glass by a sheet bent into a parabola. The adaptation of this device to shop fronts has recently been developed by Mr. G. Brown, and the effectiveness of such a scheme may be seen by viewing the interior of a motor show-room at 88 Regent Street, London, through the curved plate glass windows. No reflection of the street can be seen and only the contents of the showroom is visible from without, so that the window itself does not seem to exist. If this could be applied to pictures in public galleries, it would indeed be a boon. But there is the question of cost and the ever-haunting thought that perhaps some other and simpler solution of the problem may not be out of reach. In order to be effective, pictures hung high up would require a different curvature of glass from those on a level with the eye, and then all the varieties of sizes and shapes of canvases or panels would offer further difficulties. Would it not be as well to try first the simple device of tilting the pictures a little forward ? Why is that not done in the public galleries ? We think this would at least be an improvement on existing conditions and, if sufficiently successful under the usual system of lighting, the walls of new galleries could be built so as to lean a little inwards. It might be worth while to construct a light wooden framing that would cover one of the smaller walls of the National Gallery, to hang upon it pictures with dark backgrounds and then to tilt the screen forwards and note the improvement in visibility under the conditions of top lighting in use there.