Advanced Multichannel Lighting Control Systems in Heritage Environments: Case Study of the Cathedral of Seville

Featured Application

The multichannel luminaire systems allow a perfect color rendering of art pieces, while preserving them against light photodegradation. The presented lighting system can be applied in architectural heritage and museums.

Abstract

The appropriate preservation and color rendering of paintings and art pieces are a pending subject in architectural heritage, since, in most of the cases, lighting systems are not really focused on the conservation and suitable perception of these heritage resources, due to the limitations of standard LED lamps and lighting configurations. In this context, a multichannel luminaire system is proposed in the case study of the Cathedral of Seville, providing a variable and rich spectral distribution, which allows an excellent color perception linked to the daylight conditions, while the short-wavelength light is minimized in order to reduce photodegradation. Two scenarios are addressed: Museum of the Cathedral and Evangelist Chapel. The multichannel luminaire system is tested by means of subjective surveys and objective procedures (Farnswoth-Munsell and Natural Color System tests). The results show that the proposed spectral distribution of the multichannel system provides a better color discrimination in comparison with typical lighting systems, as well as a better preservation, defining a suitable lighting technology for architectural heritage. The novelty of this study lies in the multi-parameter approach, taking care of color rendering while photodegradation is minimized.

1. Introduction and Objectives

1.1. Background

Currently, advancements in lighting technology are markedly enhancing the energy efficiency promoted by LED light sources, with a primary focus on reducing energy consumption and corresponding CO₂ emissions [1]. Nonetheless, this progression frequently overlooks the implications of this type of luminaires on color appreciation [2], human health effect [3,4], and well-being [5]. As posited by various researchers, lighting design in architecture should encompass considerations beyond the mere distribution and quantity and light, extending to its quality [6,7,8], thereby fostering a comfortable scenario for users and a proper perception of the environment.

Most of the lighting systems currently available on the market employ LED technology, which generates a distinct spectral distribution compared to older sodium-vapor, halogen, and fluorescent lamps, resulting in a noticeable variation in color fidelity and chromaticity. Specifically, LED lamps exhibit significant variation in their chromatic perception due to the peak located in the short-wavelength spectrum [9]. LED lamps are cost-effective and provides a higher luminous efficacy in comparison with their predecessors.

In addition to the previous observations, the cutting-edge technology of LED lamps offers an interesting solution for improving color perception in architectural environments: multichannel luminaires. This type of light source, usually controlled by a DALI language, adapts the spectral power distribution (SPD) of the lamp, with the aim to render, in an optimized way, the colors of unique spaces of architectural heritage. The multichannel luminaire, composed of a set of LED lamps with different peaks and bandwidths in the visible range, can mimic the spectral distribution of daylight with noticeable accuracy, thus improving the light quality and the object’s appearance [10].

Given this context, the lighting design of museums, churches, and similar heritage buildings acquire a new tool for improving the color perception of inner spaces, creating unique atmospheres depending on the designer’s intention [11]. Accordingly, by modifying the Correlated Color Temperature (CCT), which can be deduced from the SPD of the light source, the chromaticity of the different hues of paintings can be adapted to different scenarios, changing, therefore, the observer’s perception [12]. As an example, multichannel luminaires can render the spectral distribution of a real flame, with the aim to reproduce paintings and frescoes as ancestral observers saw such elements [13], opening a wide range of potential solutions with this new technology.

The scenario described underscores the necessity for a precise evaluation of the effects induced by these new lamps on color rendering [14], since, as described above, this technology is currently used in heritage environments, where the hue fidelity and chromaticity discrimination are crucial for a suitable understanding of paintings, frescoes, and altar pieces.

There are several procedures to define the color rendering provided by a light source from a quantitative approach. One of the latest and more widespread methods for fully describing the color perception is TM-30-20, defined by the Illuminating Engineering Society of North America (IESNA) [15]. This procedure contrasts, in the CIE Lab color space, the results for 99 hue samples, setting a continuous illuminant reference which is adapted depending on the CCT of the studied light source. IESNA is currently advocating for the adoption of this method among lighting manufacturers [16]. Moreover, the Daylight Spectrum Index (DSI) [17] is a novel concept which offers a different approach for defining the color preference, using SPD fitting instead of the analysis of hue sample deviation within a color space. This innovative concept assesses the color similarity provided by a lamp in comparison with daylight, contrasting the SPD of both sources, depending on the color sensitivity functions of human vision. Thus, the goal of this concept is to determine how closely the color perception produced by a light source matches that of daylight, considering natural light as the perfect reference for color rendering.

Moreover, color rendering is not the sole variable to take into account in lighting design. The chromatic preference can vary depending on the studied scenario, and thus color rendering can be influenced by boundary conditions, such as the color of the walls and ceiling, the geometry of the inner space, or the task developed by the observer [18]. In line with this assertion, Schanda et al. [19] evaluated color fidelity in the case study of a picture gallery, selecting multichannel LED luminaires for this specific application. Bellia et al. [20] carried out an interesting study which modified not only the flux and CCT of light sources, but also the wall color of a simulated picture gallery. The results showed that a combination of the three parameters affect the color perception of the observers. Moreover, Zhai et al. [21] also studied the effect of CCT in the color perception of fine art paintings, determining that low CCT values (near 3500 K) are suitable for hue discrimination. In a different setting, Szabó et al. [22] examined color preference for a retail shop, determining the appropriate SPD for LED luminaires. More recently, Lin et al. [2] analyzed color preference across various scenarios, including retail displays, supermarkets, and restaurants, with each case study yielding distinct results. Notably, research by Royer et al. [23] evaluated color preference with 25 participants, concluding that most of the color rendering metrics do not align with color preference criteria, despite the fact that these preferences can be predicted using calculation models based on the metrics defined by TM-30-20, namely the Gamut Index (Rg) and the Fidelity Index (Rf).

The picture that emerges from the described scenario led us to conclude that the most effective way to determine the color perception—given both objective and subjective parameters—is through surveys to determine the hue preference of the observer for a specific venue, as well as objective trials, such as the Farnsworth-Munsell (FM-100) or the Natural Color System tests, as evidenced by the following studies: Houser et al. [24] conducted comprehensive research, analyzing 40 surveys to assess whiteness perception considering various LED lamps, concluding that blue wavelength light is needed to induce whiteness. Moreover, Jost-Boissard et al. [25] assessed the color quality provided by LED lamps, examining a wide range of light sources with different CCT across more than 80 surveys. Similarly, Dangol et al. [26] analyzed the precision of different color metrics using 20 surveys with different LED lamps, according to different CCTs. A recent example is the study by Gu et al. [27], which studied a set of color rendering metrics using 10 surveys, concluding that the CAM02-UCS color space is suitable for determining hue deviation. It must be noted that the performing of color tests depends on many parameters, such as the color of the environment and the age of the participants.

When developing tests to determine a light source’s ability to differentiate colors, it is crucial that the tests provide an objective quantification of the results [28]. Esposito et al. [29] defined a new procedure for measuring the color discrimination, Rd, which assigns a score based on the number of transpositions made in the FM-100 trial. An Rd close to zero indicates an excellent color discrimination, while a score greater than 16 indicates poor hue discrimination.

As can be deduced from the above, color rendering concepts are continually evolving due to the lack of solid criteria for determining a light source’s chromatic performance [30]. Moreover, most metrics focus on quantifying color deviation, neglecting the need to distinguish colors with similar hues, brightness, and chromaticity. Therefore, one of the most appropriate procedures for defining the lighting quality is the performance of objective-quantitative surveys, which can serve to determine the suitability of a lighting design in special sensitivity heritage spaces, where a careful and adequate design can improve or highlight the perception of the environment.

Finally, it must be noted that the radiation from any light source generates visual photodegradation of paintings, pictures, and other art pieces [31]. The damage produced in color perception depends on the spectrum of the source (particularly the short-wavelength radiation, which affects yellow and red hues), the illuminance (with a recommended average value between 50 and 100 lx), the exposure time, and the chemical composition of the color pigments. Several researchers in this field, such as Durmus et al. [32], have studied the appropriate spectral distribution of multichannel LED luminaires with the aim of preserving and reducing visual photodegradation and hue shifts in paintings. Therefore, the balance between color perception and the preservation of art piece is crucial in sensitive heritage spaces.

1.2. Aim and Objectives

According to the needs and opportunities described in the background, a new study is proposed, with the aim to determine the appropriate multichannel LED lighting system to achieve an optimized solution of color rendering in the case study of the Cathedral of Seville, providing a variable and rich spectral distribution, which allows an excellent color perception linked to the daylight conditions, while the short-wavelength light is minimized in order to reduce photodegradation. Two scenarios are addressed: Museum of the Cathedral, where there is a clear influence of daylight coming from the adjacent courtyard, and Evangelist Chapel, decorated with large paintings in a golden altar piece.

The multichannel luminaire system is tested by means of subjective surveys and objective procedures (Farnswoth-Munsell and Natural Color System tests). The subjective surveys were performed in the settings of the aforementioned case studies, while the objective trials were carried out in the controlled scenario of a Light Lab. The color rendering of the multichannel luminaires is compared with other luminaires types and light sources, such as halogen or standard LED lamps, as well as the simulated spectrum of daylight, in order to determine, in a comparative way, the benefits promoted by the proposed lighting system.

Finally, the selected multichannel spectrum is analyzed with the aim to determine the potential photodegradation according to the CIE procedures [31], therefore preserving the art pieces and paintings of both case studies.

2. Materials and Methods

2.1. Multichannel Luminaire System Description

The multichannel luminaires used in both the Cathedral case studies and the Light Lab are Ledmotive VEGA 07 luminaires. These luminaires were selected for their capability to render a broad set of SPDs. This is achieved through the use of seven light channels, each with a sufficient radiometric output and a narrow wavelength range per channel. Additionally, this type of lamp can be adapted for use in spotlight luminaires, which emit a narrow intensity distribution, making them particularly suitable for applications in museums and churches. Therefore, the luminous output is produced by mixing seven wavelength colors, with each spectrum determined by seven independent PWM signals. Each channel communicates with the driver via the RS-485 protocol, commonly used in serial communication systems.

The emission range of this luminaire spans from 420 to 730 nm, covering most of the visible range of human perception, as can be deduced from Figure 1.

With all channels set to their maximum level, the luminaire consumes 80 W of power and emits a luminous flux of 4460 lm. As can be deduced, the luminous efficiency is lower than that of a standard LED because this set of lamps is designed to achieve optimal color rendering rather than energy efficiency.

The photometry of the luminaire is similar to a Lambertian distribution for the luminaire used in the Light Lab, as shown in Figure 2, matching that of a typical medium-sized downlight. This luminaire model was also used in the showcases of the Museum of the Cathedral, where silver and gold art pieces are exhibited. Additionally, the paintings in the Museum and the Evangelist Chapel are illuminated by medium-distance spotlights equipped with reflectors to narrow the emission cone, focusing the light on the art pieces.

The flexibility and adaptation of the multichannel luminaires allow the rendering of different SPDs, emulating a collection of spectral distributions that permits the comparison of the proposed spectrum with those corresponding to the typical light sources used in heritage environments. Accordingly, a multichannel spectrum is proposed to optimize color discrimination and fidelity, while minimizing the photodegradation of the art pieces. This selected spectrum is compared with other typical light sources, such as standard LED lamps (both warm and cool sources, corresponding to CCTs of 2700 and 5500 K), incandescent lamp (similar to the Standard Illuminant A), and daylight (rendering a sunny sky with a CCT of 5000 K and a standard or overcast sky with a CCT of 6500 K). Figure 3 represents the spectral distribution of the selected light sources. The selected SPDs exhibit a Fidelity Index (Rf) and a Gamut Index (Rg) both exceeding 90, indicating that accurate color perception can be expected across all studied scenarios.

The multichannel LED optimized spectrum has been selected according to the following conditions:

• The simulated color rendering, defined by TM-30-20 procedure [15], must be higher than 90. The proposed SPD achieves a Fidelity Index (Rf) of 90 and a Gamut Index (Rg) of 95, providing excellent performance in color fidelity and discrimination.
• The entire visible spectrum must be covered by the SPD emission of the luminaire to provide similar chromaticity to most hues in the visible range.
• The visible photodegradation must be lower than the case of cool LED lamps, according to the CIE 157:2004 procedure [31]. Figure 4 shows the results of the visible damage of the proposed multichannel luminaire and the critical exposure duration in hours before perceptible visual damage occurs, considering an average illuminance of 100 lx from 8:00 am to 8:00 pm with a protective glass.

2.2. Case Studies

The multichannel LED system was installed in the Museum of the Cathedral of Seville and the Evangelist Chapel. Both sites were recently restored, ensuring that the artworks were in an acceptable state of preservation throughout the study process. The selection of these case studies is based on the divergent lighting conditions of both scenarios. In the museum, the lighting is significantly influenced by the adjacent courtyard, Patio del Limonar. Therefore, the spectral distribution and resulting CCT of the electric lighting must account for daylight influence. To address this, the SPD of the multichannel system is adapted to the daylight spectrum, imitating the color temperature of the natural light source to avoid distorting the hues of the ambient light. Conversely, the Evangelist Chapel lacks natural light influence, so the design focuses on suitable illumination of the paintings and proper color rendering of the altar piece, ensuring both hue discrimination and an adequate balance of chromaticity.

An initial setup was conducted in the Museum to determine the optimal placement of the spotlights, avoiding specular reflections on the varnish of the paintings from the observer’s position, as shown in Figure 5B. The goal was to cover the entire surface of the painting, optimizing horizontal illuminance uniformity. After the spotlight installation, the SPDs of the multichannel luminaires adapt their CCT according to daylight conditions, as shown in Figure 6. The natural light spectrum from the courtyard is inferred from an outdoor webcam that translates the sky color to a specific CCT, which is then interpreted by the light driver to assign a corresponding SPD to the electric luminaires.

The installation of the luminaires in the Evangelist Chapel involved placing spotlights on two rail systems located in front of the altar piece, as shown in Figure 5A. Next, the spectral configuration of the luminaires was adjusted, as can be inferred from Figure 5C, to find the suitable SPD for achieving optimized color fidelity and hue discrimination. The final results, showcasing different CCT configurations, can be seen in Figure 7.

The objective trials—which correspond to the Farnsworth-Munsell and Natural Color System tests—were conducted in the Light Lab at the School of Architecture, University of Seville, shown in Figure 8. This lab is equipped with nine multichannel LED luminaires, the same model used in the case studies of the Cathedral of Seville, allowing the same SPD to be reproduced in a laboratory environment. The luminaires are mounted on the ceiling with an opal diffuser that creates a Lambertian distribution of light. The lab’s walls are made of mirrors with an average reflectance of 97%, although neoprene sheets of different colors can be added to alter the scenario’s perception.

2.3. Subjective and Objective Trials

A subjective trial was conducted with 30 participants within the environments of the Cathedral’s Museum and the Evangelist Chapel case studies. The study sample comprised 11 men and 19 women, aged between 22 and 36 years. The participants in this study do not exhibit color blindness, and the selected age range was chosen to avoid corneal degradation associated with aging, which can impair the perception of short-wavelength colors. Participants completed a subjective test assessing their satisfaction with color appearance and their preferences regarding the lighting design for each simulated scenario, resulting in a total of 180 surveys. The questionnaire addressed the following issues:

• What is your level of satisfaction with the color rendering?
  (very unsatisfied/unsatisfied/neutral/satisfied/very satisfied)

• What is your level of satisfaction with the perception of colors?
  (very unsatisfied/unsatisfied/neutral/satisfied/very satisfied)

• How do you perceive the hue of the lighting in the space?
  (very cool/cool/neutral/warm/very warm)

The results are summarized to complement those observed in the objective trials. It should be noted that respondents’ answers may not align with the hue discrimination and color fidelity assessments conducted in the Light Lab, as psychological preferences can differ from objective color perception, as deduced from previous studies [33].

The objective trials consisted of two distinct tests designed to evaluate the observer’s ability to distinguish similar hues and to assess the color fidelity of a sample under a SPD produced by a specific light source. A description of each test is provided below:

• The Farnsworth-Munsell 100 Hue test employs 100 color caps with similar hues in four color ranges with low chromaticity (red to yellow, yellow to green, green to blue, and blue to red), as shown in Figure 9A. Participants must arrange the color caps according to their hue similarity, considering that color references are fixed at both ends of each range. Both the hue caps and light sources were randomly selected for each test and participant. This trial provides an objective measure of a light source’s ability to distinguish similar colors. The test score is determined by the number of color cap transpositions; specifically, a light source causing one transposition in the Farnsworth-Munsell trial would receive an error score of 4, two transpositions correspond to an error score of 8, three transpositions to a score of 12, and so on [29].
• The Natural Color System test utilizes a collection of color samples with varying parameters of chromaticity and brightness, identified in polar coordinates. The hues vary according to the angle, similar to the ranges in the previous test (yellow to red, red to blue, blue to green, and green to yellow), as shown in Figure 9B. Participants must identify the position of the color samples in the polar coordinates. An angular variation indicates a change in hue perception, while a variation in the parallels indicates a change in chromaticity. This test determines the observer’s divergence in perceived color from the real one under an illuminated scenario with a particular spectral distribution, and thus assesses the color fidelity allowed by a specific light source.

3. Results

3.1. Color Discrimination Test

The first trial conducted in the Light Lab corresponds to the Farnsworth-Munsell test, where 30 respondents must arrange the color caps of four hue ranges to quantify the ability of a light source to discriminate similar colors.

The scores were determined according to the number of color cap transpositions, as described in

Table 1. Score according to number of caps transpositions.

Score	Single Transposition	Double Transposition
100.0%	0	0
83.3%	1	0
66.6%	2	1
50.0%	3	1 (+1) 1
33.3%	4	2
16.6%	5	2 (+1) 1

¹ Adding one single transposition.

. Accordingly, a score of 100% implies that the arrangement of the caps is perfect, while a score of 66% indicates that there were two single transpositions or one double transposition.

In accordance with the scores defined previously, Figure 10 shows the results for the four hue ranges (red to yellow, yellow to green, green to blue, and blue to red), defining the average score for each source, the maximum and minimum values, and the second and third quartiles.

As can be deduced from Figure 10, the selected light sources offer acceptable color discrimination in most cases, although some nuances can be observed. The spectral power distributions of natural light—CIE D65 and CIE D50—achieve the best performance in comparison to other sources. Moreover, luminaires emitting warm-colored light—incandescent lamp and LED 2700 K—allow poorer hue discrimination, specifically in the red to yellow and green to blue hues. Finally, the behavior of neutral and cool luminaires—LED 5500 K and Multichannel LED (MC LED)—provides the best color discrimination, especially in the ranges from red to blue.

The results can be summarized in the analysis shown in Figure 11. The average score for all hue ranges is synthesized for each light source, defining, as in Figure 10, the average, maximum, and minimum values, as well as the second and third quartiles.

As deduced from Figure 10 and Figure 11, the best color discrimination is provided by neutral and cool light sources, such as the natural light spectra—CIE D65 and CIE D50—and the neutral and cool luminaires—LED 5500 K (LED55) and Multichannel LED (MC LED). This is because the corresponding SPDs of these light sources offer a rich spectral distribution throughout the visible range, providing sufficient energy in the short wavelength range, as observed in Figure 3. The unbalanced spectra of warm light sources—incandescent lamp (INC27) and LED 2700 K (LED27)—generate an excess saturation of red hues, producing poorer discrimination in the ranges affected by red, as seen in Figure 10A,D.

Analyzing the daylight spectrums, it can be observed that overcast or blue skies—CIE D65—provide better performance in color discrimination than sunny skies—CIE D50—mainly in the range of blue to green hues, as deduced from Figure 10C. This is because the CIE D65 spectrum offers a higher power distribution in the short and medium wavelengths—from blue to green—while maintaining sufficient energy in the long wavelengths—red hues—to properly distinguish the colors.

Finally, as observed in Figure 11, neutral and cool luminaires—LED 5500 K and Multichannel LED—provide performance similar to daylight in color discrimination. This is particularly true for blue hues, as deduced from Figure 10D, because the spectral distribution of these luminaires is higher in the short wavelength range than in the case of natural light. However, the performance of these light sources is slightly poorer than daylight for red hues, as deduced from Figure 10A, due to the unbalanced spectra in the red wavelength range.

3.2. Color Fidelity Test

The second objective trial aims to determine the fidelity of the perceived color to the real one, conducted using the Natural Color System test. This test uses a collection of color samples with varying parameters of chromaticity and brightness, identified in polar coordinates. As described in the methodology, respondents must identify the position of the color samples in the polar coordinates. Accordingly, the chromaticity deviation—colloquially identified as saturation—and the hue divergence can be quantified as separate parameters. The color fidelity is therefore the result of applying color deviation over a value of 100%; hence, a chroma fidelity score of 85% implies a deviation of 15%. Figure 12 represents the chromaticity and hue fidelities according to four color ranges (yellow to red, red to blue, blue to green, and green to yellow), defining the average score for each light source, as well as the color deviation for both parameters.

As deduced from Figure 12, the color fidelity provided by the selected luminaires is suitable for most color ranges, with some nuances, as in the case of the color discrimination test. A general overview shows that daylight sources—CIE D65 and CIE D50—provide better color fidelity in most cases, except for the red to blue range, as seen in Figure 12B, where neutral and cool LED lamps—LED 5500 K (LED55) and Multichannel LED (MC LED)—offer better results. These electric light sources allow suitable fidelity in most color ranges, with a chromaticity deviation lower than 10%, except in the yellow to red hues, as observed in Figure 12A. Moreover, warm LED lamps—incandescent lamp (INC27) and LED 2700 K (LED27)—give poorer chromaticity and hue fidelity than the other luminaires, mainly in blue to yellow hues, as deduced from Figure 12B,D. This is because, as explained in the previous trial, the spectral distribution of the luminaires emitting warm-colored light is unbalanced, providing more energy in the long wavelength range and less in the short wavelength range, as seen in Figure 3.

3.3. Color Preference Test

The final trial, conducted in the case studies of the Cathedral of Seville, corresponds to the color preference test. It must be highlighted that, as explained in the methodology, the SPD of the luminaires is the same as that utilized in the Light Lab trials, with the aim of linking the subjective results to the previous ones, performed using the Farnsworth-Munsell and Natural Color System tests.

Figure 13 presents the responses of 30 participants regarding their color preference and appreciation of the art pieces in the Museum of the Cathedral and the Evangelist Chapel. The responses are classified from “very unsatisfied” to “very satisfied” for each studied light source.

As deduced from Figure 13, and unlike the previous trials, daylight sources—CIE D65 and CIE D50—are not particularly comfortable for participants, likely due to the fact that the Cathedral environment—the surrounding chapels and the main venue of the church—is illuminated with luminaires emitting warm-colored light (mainly incandescent and warm LED lamps), affecting the overall color perception of the observers, who perceived different CCTs in their field of view. This assertion contrasts with the excellent performance that natural light exhibits in color discrimination and fidelity. In contrast, neutral LED luminaires—Multichannel LED (MC LED)—provide the best results due to their ability to accurately render colors, while the CCT of 4000 K is closer to the Cathedral’s environment, producing a lower divergence with the color temperature of the adjacent spaces. Finally, warm light sources—the incandescent lamp (INC27) and LED 2700 K (LED27)—provide a poorer perception, likely affected by lower color fidelity and hue discrimination. This final test highlights the importance of multichannel LED lamps, which allow the balance between color temperature and color rendering.

4. Discussion

As demonstrated by the results shown in Figure 10, multichannel LED luminaires achieve excellent color discrimination, obtaining a score higher than 80% for all hue ranges. These luminaires are surpassed only by daylight—CIE D65 and CIE D50—in red to yellow hues, and by cool LED luminaires—LED 5500 K (LED55)—in green to blue hues. This is because the daylight spectrum is richer in the long wavelength range, and cool LED lamps provide more energy in the blue-green range. However, it is important to note that the proposed multichannel spectra allow for lower photodegradation compared to the aforementioned light sources, thereby preserving artworks more effectively. The overall analysis of color discrimination, shown in Figure 11, confirms the good performance of the multichannel lighting system, achieving an average score of 86.8%.

Regarding chromaticity fidelity, and as deduced from Figure 12, the multichannel system achieves an average score of 88.6%, with exceptional performance—over 90%—in the color range from green to blue. This score is only surpassed by overcast daylight (CIE D65) and cool LED lamps (LED 5500 K), although these light sources, as previously mentioned, result in shorter preservation of artworks. Additionally, in terms of hue deviation, the multichannel luminaire achieves a fidelity of 80.0%, higher than that of the other light sources, demonstrating its great potential in color rendering due to its balanced spectral distribution.

The excellent results in color discrimination and fidelity provided by the multichannel lighting system are evident in the responses from participants in the subjective trial conducted at the Cathedral of Seville. Observers, as shown in Figure 13, prefer neutral or warm light, influenced by the surrounding spaces linked spatially to the Museum of the Cathedral and the Evangelist Chapel. The spectral power distribution of the multichannel luminaire system produces a neutral correlative color temperature (CCT), compatible with lighting systems emitting warm-colored light used in the adjacent chapels. Quantitatively, as illustrated in Figure 13, 40.0% of the observers perceive the color appearance as neutral, and 44.5% find it satisfactory or very satisfactory. Therefore, the proposed lighting control system not only ensures suitable color rendering and hue discrimination but also provides adequate comfort for observers, aiding in the preservation of artworks in heritage environments.

It is important to note that color quality—encompassing both color fidelity and hue discrimination—is not the only factor influencing the perception of artworks or altar pieces. Luminance uniformity, along with the minimization of glare, also plays a crucial role in accurately reproducing heritage objects. Therefore, the placement of spotlights in relation to the observer’s position is critical for enhancing the optimal perception of the artwork. This is particularly important because the specular reflection from the varnish on paintings can redirect light and create glare, potentially impairing visual appreciation.

The proposed multichannel luminaire system introduces a novel approach for enhancing both the color rendering and preservation of artworks in heritage environments. The study presented is limited to the specific case studies described in the methodology; therefore, further analysis is needed to assess its effectiveness under different conditions. Nevertheless, the potential of this new lighting system offers a valuable tool for improving the perception and preservation of architectural heritage.

5. Conclusions

Emerging technology in control systems for multichannel LED luminaires offers valuable tools for lighting designers, enhancing the color rendering of artworks, paintings, and architectural details. This technology ensures high fidelity in color reproduction and accurate hue discrimination while also considering the subjective preferences of observers. Additionally, it minimizes photodegradation of oil paints on canvas, rag paper, and textiles due to its low energy emission in the short wavelength range.

The outcomes of this study present a multichannel luminaire system that delivers excellent color rendering, achieving a Fidelity Index of 90 and a Gamut Index of 95, while also ensuring objective color fidelity and discrimination, as confirmed by the survey results. The system’s spectral power distribution (SPD) is balanced to cover most hues in the visible spectrum, minimizing visible photodegradation—according to the CIE 157:2004 procedure—and thereby preserving artworks in architectural heritage environments.