LR&T essentials
September/October 2023
ARTS, SHOOTS AND LEAVES Iain Carlile looks at two of the latest papers to be published by Lighting Research and Technology which variously examine the effect of lighting conditions on plant growth and the visual appearance of artwork undinger and Houser have studied the lighting of artworks, in particular how the level and nature of illuminance affect the perception of colour. They note that due to conservation guidelines restricting illuminance levels for sensitive artworks, the illuminated object can be perceived as being less colourful, a phenomenon known as the Hunt Effect. Previous research has shown that light sources with a red saturating gamut consistently increases peoples' perceived colour saturation and personal preference when viewing an artwork, say the authors, therefore compensating for some of the perceived desaturation associated with the Hunt effect. They conducted a study with 31 naïve participants viewing two paintings in a mock
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art gallery setting. The artworks, one watercolour, one acrylic, were shown under nine varying presented scenes with the participants individually evaluating the paintings for preference, saturation and naturalness. The lighting scenes remained consistent at 3000K CCT and 50 lux illuminance. The presented scenes were varied in their red gamut (TM-30 96 ⩽ R*g ⩽ 124) and their position above or below the blackbody locus (-0.0212 ⩽ Duv ⩽ 0.0036). From the results of the experiment it was found that it was possible to map preference as an interaction between the R*g and Duv values, and that increasing R*g consistently increased both personal preference and perceived saturation. Ahamadi et al have investigated the effect of different light sources on the physiological control of flowering and vegetative growth of a
⊳ Importance of different objects in the watercolour painting (Fine art under low illuminance: Gamut and tint, Mundinger and Houser)
popular houseplant, the African violet. The experiment involved exposing the plants to six months of electric illumination for 12 hours a day. Four different light sources were tested including: 1 LED – monochromatic red, 2 LED – monochromatic blue, 3 LED – mixed 75 per cent red plus 25 per cent blue, 4 fluorescent light (cool white). The light source positions were adjusted for a uniform photon flux density (118 μmol m−2 s−1 ± 6 μmol m−2 s−1) on the plants’ leaf surfaces. The plants were checked twice a week and investigated for possible flower emergence, number of flowers and stage of openness of flowers. At the end of the experiment the size of the flowers was measured (diameter and peduncle length) and the plants were also measured for their leaf thickness and weight from which the leaf area was estimated. The results of the investigation revealed that the blue-LED-illuminated plants were superior in their flowering qualities but were smaller and more compact in size. The plants grown under red LEDs and fluorescent light significantly produced leaves with the highest area. Blue LED light produced the thickest leaves with red LED light producing the thinnest. The authors conclude that LEDs can be use as an effective tool to manipulate the visual qualities of plants. Iain Carlile, FSLL, is a past president of the SLL and a senior associate at dpa lighting consultants
Lighting Research and Technology: OnlineFirst In advance of being published in the print version of Lighting Research and Technology (LR&T), all papers accepted for publishing are available online. SLL members can gain access to these papers via the SLL website (www.sll.org.uk) Fine art under low illuminance: Gamut and tint J Mundinger and K Houser Light source spectrum influences long-term flowering cycles and visual appearance in African violet (Saintpaulia ionantha Wendl) L Ahamadi, M Matloobi and A Motallebi-Azar
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sll.org.uk