78 CONTENT IN ENGLISH 027 CD art preserve its quality or will there be a difference that could interfere with the interpretation or understanding of the works of art, by the spectator, especially in the case of paintings? It’s not always easy to determine the quantitative or scien- tifically proven aspects that influence a perceptive “sensa- tion”. This work for the Master Finals of the UPC, by the ar- chitect Nataly Revelo, investigates the posible connections between perception parameters and impressions, when applying lighting on a specific painting with a halogen lu- minary and a Led luminary. INTRODUCTION Light is a language that conditions everything that we per- ceive visually. It is not just a physical or technical measure but a form of communication at a perceptive and sensory level. By definition, light is the electromagnetic energy corresponding to the visible spectrum, which makes pos- sible the perception of our surroundings through the organ of sight. Even though light as energy is only one, there are different sources of luminous output, each with its own qualities and particularities which have defined their use. In this context, one of the more widely used traditional sources of light has been the incandescent Halogen. It is used practically in every area due to its chromatic and lu- minous characteristics. However, in the last few years, one of the most important innovations in lighting emerged: Led light. It has significant attributes regarding energy ef- ficiency, power and service life, representing a huge tech- nological advance in this field. Nonetheless, in both cases, a technical perceptive study on the influence of light on individuals is pending. Regarding architecture and art, light acts as an element which is not only functional but a harmonic component of the space or object that is illuminated and will be perceived by an observer. When a connection between light – object -individual happens, that important factor that is percep- tion intervenes. The whole purpose is for light to create the opportunity to receive the image as faithfully as possible and without distortion. This is why it is necessary to find the most adequate source of light so the observer can have the best experience. When studying lighting of museums, it’s important to consider that the works of art are the reason of being of these spaces. Here, the light projected on the pieces usually comes from spot lighting or an accent light, so the focus of this investigation is directed to the study of light and its influence in the perception of a work of art, specifically an oil painting. An important point that is taken into account is the change in the traditional mode of illuminating mu- seums, with the substitution of Halogen lamps for Led. On the basis of these conditions, a question arises: What is the best light to appreciate a work of art and what is its influ- ence in the visual perception? Against this background and these questions, this article presents an investigation on the technical and perceptive relation of lighting using Halogen light and Led light, and its effect on the visual perception of a work of art, through the study of their chromatic and luminous parameters. With this work, we strive to make a contribution in the use of light sources, considering the importance they have on the perception of pictorial works. HYPOTHESIS AND OBJECTIVES Considering that light affects the visual perception of an art work, we propose that each source of light creates a technical-perceptive relation, and suggest that Led light creates a better visual perception of the paintings. From this hypothesis, we pose as main objective: - Determine the source of light which offers a better ap- preciation of a painting, according to its technical param- eters and the visual perception of the observer. As part of the specific objective, we establish to: - Analyze and contrast the characteristics pertaining to Led light and Halogen light in the lighting of works of art. - Asses the relation between the technical parameters and the visual perception in both sources of light. - Identify how the type of light used to illuminate an art work affects the visual perception of the observer. METHODOLOGY The investigative work is presented as a comparative, tech- nical and perceptive study developed initially by identify- ing the problem in connection with the influence of the source of light in the perception of an oil painting. We es- tablished the state of the art in which we would analyze the background, fundamentals and framework related to the use of Halogen lights, Led lights, lighting of art works and visual perception. Later, the experiments took place to verify the hypothesis proposed. In accordance with the theoretical bases analyzed on the state of the art, the ex- perimental study was established in two phases: technical and perceptive. Technical Phase The technical part consisted in measuring the parameters of Led light and Halogen light. To the effects of this study we considered: the color temperature, the illuminance, the irradiance, and the luminance. The investigation fo- cused on these luminance and chromatic characteristics, because through them it is possible to establish the tech- nical differences among the two light sources and the impact they have on the perception of the illuminated art work. To obtain a balanced comparison it was necessary to have the same level of lighting or illuminance when using both types of light, in order to evaluate the quality of the light, apart from the luminous flow or an increase in the level of lighting. When obtaining the same amount of light on the surface with both light sources, the per- ception could be evaluated under the same conditions. Likewise, the appearance of the light had to correspond in both sources, for which lamps with a color temperature of 3000K were used; this is the recommended value for a correct chromatic reproduction. Regarding luminance and irradiance, the values obtained from these parameters were related to the level of light- ing, energy, brilliance and colors of the painting. When measuring the luminance, what is being recorded is the light that bounces and the observer perceives, and which corresponds with wave longitudes and hence with the reproduction of colors on the painting. Whereas, when ir- radiance is measured the result is the energy that reaches the work of art. Regarding luminance and irradiance, the values obtained from these parameters were related to the level of light- ing, energy, brilliance and the colors of the painting. When measuring the luminance, you are recording the light that bounces and the observer perceives, and which corresponds with wave longitudes and hence with the reproduction of colors on the painting. Whereas, when irradiance is meas- ured the result is the energy that reaches the work of art. The measurements on the illuminated painting allow a technical comparison between the parameters and deter- mine the behaviour of each type of light. Perceptive Phase The second phase focuses on the perceptive study through a quantitative – experimental method using a survey. The assessment consists of the relation between the technical and visual perceptive parameters found on the work of art when illuminated with Led and Halogen lighting. In this way, it is possible to interpret the influ- ence of light in the uniformity, contrast, glare and percep- tion of the work of art. In general, with the relation between quantitative data and qualitative perception, we seek to value the influ- ence of Led and Halogen light on a pictorial work of art, to discover which light translates in a better appreciation of the art, considering the technical parameters that in- tervene on it. WORK OF ART AND LUMINARIES The painting used for the experiment is an oil painting measuring 40 X 60 cm. This work of art was chosen for the experiment because we could have access to it, and due to its chromatic characteristics, with warm and cold colors which were necessary for the investigation. The painting has color contrasts, lighter areas and darker areas, which would show the influence of light on the perception of the work of art. (Figure 1) With regard to the luminaries, we used projectors that are commonly used in museums, so that the experiment would show data on a real setting. For the Halogen light we used a projector type Shuttle from Iguzzini and a pin- based lamp from the Clar brand, which had a luminous flux of 2000 lm, efficiency of 12 lm/W, IRC of 100, power of 100W and voltage of 24 V. For the LED light, we used a projector type Optec Floodlight from Erco, with luminous flux of 1080 lm, efficiency of 72 lm/W, IRC higher than 90, power of 15 W and voltage of 220 V. In both cases, the color temperature was 3000 K and they were installed on elec- trified rails. In addition, to gather the technical parameters data, some measurement tools were needed, among them the lux meter, to measure the level of lighting (lux), luminance meter for the luminance (cd/m2) and the photo radiometer for irradiance (W/m2). LOCATION OF EXPERIMENT The research was done at the “Taller de Estudios Lumínic- os” (Workshop for Lighting Studies) TEL of the “Escuela Superior de Arquitectura de Barcelona de la UPC” (Supe- rior School of Architecture of Barcelona of the UPC). Here, we had access to an area, with a white panel at the back of the room that measured 3m. in height. The painting was placed on the panel for the gathering of data and the subsequent perceptive survey. The painting was placed at eye level of the observer, considering 1,60 m. as an average height. The eye level was centered at the mid- dle point of the painting, and centered symmetrically in horizontal direction. The projectors were installed in electrified railings to the left of the work of art (Figure 2). This placement was cho- sen to minimize the shadows that the observer might cast and to avoid the glare caused by the reflection of light on the exposed object. Furthermore, the luminaries were di- rected towards the bottom third of the painting in order to achieve a more uniform distribution of the lighting. Lastly, it was decided that the position of the observer should be in front of the painting, at a distance of 1,50 m. so that the lighting could be perceived properly, and to avoid any discomfort in the observation.