2018 CONTENT IN ENGLISH 79 PROCEDURE After setting the work place and installing the projectors, we proceeded to take measurements of the lighting pa- rameters: illuminance, luminance, and irradiance, using the Halogen light and Led light. 25 points were marked on a reticulated mesh, to take measurements in the whole area of the painting. The first requirement was that the illuminance had to be under 150 lux, which is the allowed value for oil paintings. We had to control the position of the projector, the distance to the painting and the projection angle of each source, without producing glare in the observer. Since the level of lighting had to be the same for the Halogen and Led lights, an average of 108 lux was obtained in both sources. Additionally, the luminance on the painting and back- ground was measured, in order to obtain the relation of contrast between background and object. It is important to consider that the luminance values are related to the level of brilliance perceived from the work of art and has a cor- relation with the colors of the painting. Lastly, the measurement of the irradiance was done to ob- tain the amount of energy that reaches the work of art, and in this way discover the influence of the lighting on the per- ception, according to the level of energy on the painting. With these technical parameters a description of Led and Halogen lighting, independently, was accomplished, establishing a relation between the properties of each lighting source. After this analysis, came the technical comparison between the parameters of both sources in order to find their similarities and differences. Finally, the connection between light and perception was established through the observation of the illuminated work of art and the survey, interpreting the existing, if any, correlation between the technical and the perceptive parts, using the results found in the two section of the experiment. Accord- ingly, what was assessed was the influence of these meas- urements on the visual results of the painting, relating how the light that reaches the work of art has an influence on how it is perceived. The present technical analysis was carried out on the paint- ing, by sections, taking measurements of each section of the painting and of its chromatic diversity. When compar- ing the painting illuminated with Halogen lighting and with Led light (Figure 3), the data from each light source was registered and its behavior assessed. First of all, the value of the parameters in both types of lighting would be decreasing due to the position, to the left of the painting, of the Led and Halogen projector. With respect to the contrast in luminance between the back- ground and object, a relation of 1:5 was obtained in the case of the Halogen light, and of 1:4 for the Led light, con- sidering that in both cases, the contrast presented a bal- anced relation that should not cause any discomfort to the observer. Regarding the illuminance, the same value was obtained from both sources, whereby the perception of the work of art would not be affected by the level of lighting or a difference in the amount of lighting received. Accord- ing to this, perception depends on the characteristics of each light source and not on the amount of light shining on the painting. As we mentioned before, irradiance and luminance depend on the amount of energy the material can absorb and the color scheme of the painting. If there are areas with lighter colors, luminance will be high while with opaque colors, luminance would be low. Irradiance According to the data obtained, we verify that more light reaches the work of art when using Halogen lighting (Figure 4). This is associated to the lamp power which is stronger in Halogen sources of light than in Leds. Furthermore, ir- radiance has a tendency to decrease much like illuminance, evaluating that the energy level that reaches the painting will react to the quantity and direction of the projected light. Even with this tendency, the behavior of irradiance with Led light is much more uniform in the general lighting of the work of art, evaluating that the painting will be well illuminated without excessive energy. Luminance Luminance shows variabiality in both sources of light, pro- ducing more elevated peaks of brilliance when using Led (Figure 5). This tendency is not affected by more or less light because this parameter is related to the colors of the painting more than to lighting. On the other hand, Led light enhances the painting’s own brilliance, differentiating the tones and luminosity with ease and in more detail, and en- hancing the intensity of the colors without increasing the level of lighting. In addition, comparing the luminance with the irradiance, we observed that with less energy from the Led on the work of art, there is more intensity of light than when the Halogen source was used. Illuminance The tendency of illuminance is decrescent, which results in a higher level of lighting on the side closest to the pro- jector than on the other side (Figure 6). Furthermore, we observed that the lighting obtained with Led was more uniform than the lighting produced by Halogen light. There was a lower range of difference in light between the end positions of each section; thus, the difference in the light- ing is less pronounced with Led. We also observed that re- gardless of the amount of light that reached the art work, the illuminance was still higher with Led. In this case, with lower emission of energy and a level of lighting similar to the Halogen light, Led offers a clearer and more uniform perception of the work of art. PERCEPTIVE ANALYSIS A perceptive analysis was done using Led and Halogen light to illuminate a pictorial work. The technique for data col- lection was the survey, carried out through a quantitative - descriptive -questionnaire, where the perception criteria and the technical data obtained were compared. The ob- jective was to define the type of lighting that would offer the best perception of the painting. The variables used in the study where: Halogen and Led light as independent variable, and perception of the work of art as dependent variable. Among the perceptive criteria the following were included: level of brilliance, color intensity, definition of forms and shades, discomfort in the observation and general appre- ciation of the painting under each source of light. Regarding the sample, observers with a university degree and a knowledge of art and light were chosen, with no gender or nationality differences. The age of the partici- pants ranged between 25 and 35 years of age, focusing on the visual perception of the observer and nothing more. The total sample of the investigation consisted of 23 par- ticipants, 16 women and 7 men. The survey was designed in three sections: questions Light A, questions Light B and comparative questions among Light A and Light B. In the section of questions Light A, as well as in Light B, an independent questionnaire was posed for the painting illu- minated with Halogen light and Led light respectively. The participants were not informed of the lighting used, so as to be free of bias that could steer towards a specific answer. The participants were able to evaluate how well they per- ceived colors, shapes, shadows, brilliance and the presence of opaque areas in the illuminated painting. In addition, the visual comfort was questioned, when asking if the lighting of the painting created any discomfort in the observer. The evaluation of the questions was rated in a scale of 5 that went from very high, high, normal, low and very low, considering intermediate points so as to avoid absolutizing any answer. In the section of comparative questions from Light A and Light B, photographs of the illuminated painting with both sources of light were used, and they were displayed so the observer could see both images at the same time. This methodology was used with the objective of obtaining a more direct visual comparison, stemming from the possi- bility of contrasting the perception and lighting preference when looking at both photographs at the same time. The survey was completed in 10 minutes in groups of up to 5 people, allotting 3 minutes for the Light A questions, 3 minutes for the Light B and 4 minutes for the comparative, with a transition of 15 seconds between sections. With this, results were obtained on the observation of the painting under each light, and on selection and preference by com- paring the images observing them at the same time. RESULTS Based on the technical study of the investigation, the fol- lowing results were obtained: - A more uniform level of lighting is achieved with Led lighting when compared to Halogen. - When both sources are under the same levels of lighting, the levels of luminance tend to be higher with Led. - Irradiance has a lower value and more uniformity with Led than with Halogen. - The contrast between background and object maintains an adequate relation, so both light sources are free of glare or visual discomfort. With regard to the results of the individual section of the survey, observing the illuminated painting with each source of light, we concluded that: - The majority of participants had a better perception of colors, shapes and profiles with the Led light when com- pared to the Halogen light. - Regarding the painted shadows, Led light tends to pro- duce a perception of medium to high intensity, while the Halogen light makes them appear with a medium to low intensity. According to this, Led light enhances color in- tensity more than Halogen light. - The majority of observers perceived brilliance at a high to medium level with Halogen light, , whereas with Led a normal level between high and low was obtained, and with a more uniform distribution. - None of the lights cause discomfort in the observation, as a result of lack of lighting or due to glare. When evaluating the simultaneous comparison between the images illuminated by Led light and by Halogen light respectively, it was determined that: - With Led light there is better appreciation of colors, in- tensity of warm and cool tones and of definition of shad- ows. Furthermore, this light was preferred in the critical spots of greater luminance and in the general apprecia- tion of the work of art. When doing a direct and simul- taneous comparison, the differences between images become more perceptible, and it is easier to compare how the painting is perceived with each source. The tech- nical data, which indicates that Led light is more uniform and has higher luminance, implies that this source of light creates more defined shapes, details and enhanced colors, which shows in this part of the experiment.