Church Interior Lighting: A Semantic Differential Research

Lighting is essential for improving the visual conditions and meeting the needs of space users. It serves both quantitative and qualitative roles in a building. Furthermore, the lighting in a house of worship fulfills visual tasks and creates atmosphere for worship. This research aims to explore the perception of the Nazarene Christian Church (GKN) Filadelfia congregation regarding to the interior lighting conditions of their church using the semantic differential method. The results show that the congregation perceives the lighting is suitable for visual tasks, but the interior design falls short in creating the atmosphere required for a place of worship. This includes aspects like identity, warmth, intimacy, mystique, hierarchy, and expansiveness. The interior lighting of the Nazarene Christian Church Filadelfia needs to be redesigned to align with the church’s purpose and meaning, in addition to meet visual requirements.


Introduction
Light is a concept that depicts the human world in an endless series of the visual permutations by revealing colors, textures, distances, and even changes in time [1].Consequently, the quality of lighting can significantly impact the creation of an interior atmosphere within a building, influencing both physical and psychological aspects and even providing spiritual value [2].This is due to its ability to connect humans with places considered holier, higher, and give more sense of eternity [3].The quality of lighting can be qualitatively assessed through tools such as user questionnaires, quantitatively measured through parameters like light intensity, or a combination of both [4].
According to Unver & Enarun as cited by Palealu et al., lighting is also significantly required in places of worship, especially in church, because humans need space to fulfill religious obligation and experience the values associated in addition to the comfort.Church lighting generally aims for a warmwhite color tone with a diffused and shadow-free direction.Lighting in the pulpit and altar areas is specifically required to be brighter, at 300 lm/m 2 at a vertical position and local distribution.Meanwhile, congregational seating area is expected to be at 100-200 lm/m 2 with a horizontal position and a general distribution.This means the two areas can be distinguished based on lighting quantity, positioning, and distribution.
Nazarene Christian Church (GKN) Filadelfia is an example of a place of worship that needs lighting design method to fulfill the objectives previously stated.This necessity arises from the building's design, IOP Publishing doi:10.1088/1755-1315/1301/1/012006 2 which limits the penetration of natural light into the interior, resulting in a heavy reliance on artificial lighting for both quantitative and qualitative aspects.Thus, this research aims to evaluate perception of the congregation about the interior lighting design of church.This is necessary because they depend highly on lighting conditions to carry out their activities effectively.The outcomes of this research are expected to serve as a guide to designing artificial interior lighting for church.
A hierarchical method, encompassing both quantitative and qualitative aspects, was employed to produce more in-depth results.The first phase of data collection was conducted through the quantitative method, and this involved gathering existing data on the interior lighting of church by measuring illumination levels or light intensity using a lux meter [5,6].Illumination level, measured in lux units, refers to the amount of light falling onto a surface area [7].The light intensity data at both the congregation seating and altar areas were retrieved and compared with lighting standards to obtain the initial data on lighting conditions of the interior aspect of church.
The second phase of data collection involved a qualitative method, which assessed the quality of space based on the visual perception of users, using the semantic differential method.This method, developed by Charles E. Osgood, is designed to understand the connotative meaning of a concept.The measurement process entails observing the similarities and differences in the assessment of opposite words on a certain scale by the respondents [8].Semantic differential was identified as one of the most commonly used psychophysical methods in lighting research while psychophysical was applied to explore the response of a person to physical stimuli received such as lighting levels [9].
The semantic differential data were collected using questionnaires given to a total of 53 respondents including 27 who completed the questionnaire in the morning and during the day as well as 26 in the evening, distributed for completion inside the church building, with all artificial light sources active.All respondents were members of GKN Filadelfia with prior visual experiences in the church building.The respondents' aged between 18 and 60 years, with over 60% of women.Nearly half of them had normal eye conditions, while the rest experienced myopia and/or astigmatism.They were asked to select one of two opposite words related to lighting conditions.Notably, 23 adjectives and opposite words were formulated for evaluation by the respondents, with values ranging from -5 for negative words to +5 for positive words.The collected data were further processed to determine the average values for the congregation seating and altar areas in the morning and afternoon.

Literature review 2.1. The role of lighting in the interior
The activities conducted within a space, including the interior of church, are usually influenced by lighting conditions [10].This led to the focus on spatial lighting using both the quantitative and qualitative methods.Lighting was discovered to require a subjective perspective despite the importance of the quantitative method [11], because it affects the psychological aspect of space users [12].This was further confirmed by previous research that lighting design could evoke psychological impressions in space users [13].Therefore, a subject-oriented method was deemed appropriate to address the challenges associated with lighting design [14] within the interior space.Another research also showed the need to consider context and explore creative design in the process of designing lighting for a space [15].Meanwhile, the generalization of the visual quality of lighting was found not to be possible due to the significant influence of the subject perception AS Mentioned by Lam.This showed that interior lighting could not be based only on the required standards but also on the physiological and psychological needs of the space users.

Church interior lighting
Space was identified as one of the crucial elements in architecture [16] due to its ability to provide experience as mentioned by Kant [17] as well as deliver beauty and significance to the users [18].The same trend applies to the interior design of church which can provide meaning to the users.A space is considered integral to existence because of its role in the physical environment.For example, the space between heaven and earth symbolizes the concept of in-betweenness [19].Therefore, one timeless task IOP Publishing doi:10.1088/1755-1315/1301/1/0120063 of architecture is to embody existential metaphors, manifesting human existence on Earth through space and place, to achieve an ideal living condition [20].
Church serves as a space for humans to worship their God and constitutes a realm between the transcendental heaven and the earthly plane.The realm requires a space to accommodate the needs of worshippers.This leads to the consideration of artificial lighting as an effective means to evoke a sense of sacredness within church [21] to enable the connection between humans and their Creator.Light holds spiritual value and influences the human quality of life, thereby leading to its consideration as a sacred element.It symbolizes the existence of God and serves as a link between humans and the Creator in Christianity.Lighting can also create meaning and enhance quality of the interior of church [22] and serve as a space to bridge the gap between humans and God.To achieve this transcendental connection, a user-oriented lighting design approach is essential, focusing on the needs of space users as subjects.
Several perceptual lighting quality variables are expected to emerge within church as a place of worship.Some of these include solemn, no glare, symbolic, identity, sacred, direct, simple, warm, intimate, mystical, glorious, hierarchical, contemplative, spacious, and populist as listed in Table 1 based on research conducted by Mandala [23], Palealu et al., and Intan & Arifin.Therefore, the words selected to depict the functionality of lighting in some previous research include clear, sacred, beautiful, and liked [24], beautiful, simple, and liked [25], as well as bright, clear, appropriate light color, and adequate light pattern [26].Some additional words were also included in this research based on the objectives.

Research objects and locations
GKN Filadelfia is a 40-year-old Protestant Christian church located in Yogyakarta, Indonesia.It boasts approximately 150 members and has hundreds of sympathizing congregants, resulting in a total congregation of more than 1,000 people.In the new normal era, the church conducts four worship services every Sunday, with scheduled times at 07:00, 09:00, 16:30, and 18:30.The optimization of its capacity, achieved through the expansion of the worship space, has led to a reduction in natural light access on the northern side.Field observations also reveal efforts to limit natural light access on the southern side to accommodate artificial ventilation, resulting in a heavy reliance on artificial lighting.Furthermore, it was observed that artificial lighting is more concentrated in the pulpit or altar area, as compared to the congregational seating area.The light source in the congregational seating area was found to include LED strip lights located on the wooden ceiling at a height of approximately 5 meters from the floor as indicated in Figure 1a.CFL downlights were used as additional lighting on the northern side of the space to illuminate the circulation area as indicated in Figure 1b.Functionally, the congregational area was equipped with benches for the congregation to sit as well as to conduct some other activities during worship such as praying, singing, listening to sermons, and reading sacred texts.Apart from its use for worship, church space was also observed to serve other activities such as assembly meetings and other gatherings.
The light source in the sitting room was discovered to be positioned right above the seating area which was further divided into two parts, the north and south sides, and separated by a circulation path in the middle.The observation also showed that the light source was divided evenly for the two parts with 6 LED lamps each while the circulation area was illuminated by 6 downlights.Moreover, the altar area on the west side was illuminated by downlights as indicated in Figures 1.

Light intensity
Light intensity was measured at several points in church building at night when all artificial light sources were on.The results showed a significant difference between the light intensity in the altar area and congregation seating area as presented in Figures 2 and 3.The average quantity of light in the altar area was found to be 150 and maximum of 200 lux while the congregation seating area had an average of 40-50 lux which was relatively the same as the value for the circulation path on the north side with 40 lux.This difference showed that illumination in the altar area was much higher than in the congregation seating area and circulation pathways.
The standards for light intensity within church building require 300 lux/m 2 for the altar and pulpit areas as well as 100-200 lux/m 2 for the congregation seating area as mentioned by Unver & Enarun cited by Palealu et al.This showed that both areas failed to meet lighting requirement as observed from their range of 150-200 lux/m 2 and 27-106 lux/m 2 respectively.However, the choice of light color was found to be appropriate as indicated by the usage of warm white with a yellow accent on the cross and altar which minimized the shadows on the face of the preacher.

The Visual perception of the interior lighting
The visual perception of the interior lighting conditions in GKN Filadelfia by the congregation was discovered to be important in retrieving qualitative data.According to Steffy [27], the physiology of space users could be influenced by lighting due to its ability to stimulate a response from the brain.This that lighting can have physiological and psychological effects on space users, ultimately shaping their perception of spatial conditions.Therefore, according to Sanoff, the measurement of visual perception was necessary to provide a more objective assessment of space quality and complement the quantitative data obtained from measuring light intensity.According to Lam, this was necessary because good lighting could produce good visual perception and meet the visual needs of space users.
Osgood, Suci, & Tannenbaum cited by Sanoff mentioned that the semantic differential method was applied to measure the visual perception through a bipolar scale.The process involved displaying the adjective words related to the feelings of the congregants about the interior lighting conditions of the GKN Filadelfia building and their opposites on a scale ranging from -5 to +5.The selection of these words was guided by the research questions, aimed at assessing visual perception based on functionality, which encompassed gesneral activities like reading, walking, discussions, as well as specific activities such as worship.The bipolar scale used in this research is presented in the following Figure 4.The visual perception was measured directly in church building to allow the respondents to respond based on the actual condition.A total of 27 GKN Filadelfia congregants were used as respondents during the day and at night and the data produced are presented in the following Figures 4 and 5.The results showed that they tended to be generally satisfied with the existing lighting condition as indicated by the variable values above 0 such as "do not like-like" with values more than 2 on a scale of -5 to 5.Meanwhile, perception was found to be different between morning-afternoon and evening worship.This was indicated by the fact that a smaller value was recorded during the morning-afternoon compared to the evening while the variables observed to be almost the same were "glare-non-glare", "complex/busysimple", and "crowded-broad".Moreover, the altar area had a higher rating value than the congregation seating or worship area.The variable with the most extreme value in the altar area was found to be not "obvious" and not "mystical or mysterious", leading to its designation as neutral.Perception related to the visual tasks.The quantitative measurements using a lux meter produced below-standard light quantity data but the visual perception measurements using a semantic differential showed that lighting in the congregation seating area was quite "bright", relatively "clear", and "not dazzled" as indicated in Figures 4, 5, and 6.The evening condition codenamed "Morning Average" was observed to have received a more positive response than in the morning and afternoon codenamed "Night Average".This was associated with the absence of natural light sources outside the building in the night that affected the contrast of the interior lighting.Meanwhile, daylighting affected the interior in the morning-noon even though the access to natural light in the building was very limited.The difference was also possibly due to the age because the respondents used for the morning-noon survey were recorded to be at an average of 38 years while the average age of those for the evening was 22 years, and this could have affected their assessments of lighting quality.
Perception of the congregation about the visual task of lighting in the altar area in Figure 4 was found to be better compared to the congregation area in Figure 5 because it was brighter, clearer, and less dazzling.This was observed to be in line with the quantitative results that lighting quantity in the altar area was higher than in the seating area.Meanwhile, lighting at night was discovered to be better in the altar area than in the morning and the same was also reported for the seating area.
The responses on the colors, patterns, alignment, and beauty of light in both areas were discovered to be relatively good and tended to lead to maximum points.The results showed that the respondents were relatively satisfied with the visual conditions produced by existing lighting in the two areas.This was different from the results of the quantitative assessment that the conditions were far from the standard requirements for prayer rooms.The difference showed that the quantity of lighting was not always in line with the subjective assessment of the space users.
3.3.2.Perception of the meaning.Perception theoretically expected to be present in the interior lighting design of church include solemn, symbolic, identity, sacred, directing, simple, warm, intimate, mystical, glorious, hierarchical, contemplative, spacious, and populist perception.However, the negative pole was not generally assessed but the meaning associated was found to be lower than other evaluations.The five variables observed to have the lowest average value in the altar area were "obviousmystical/mysterious" with 0.9, "cold-warm" 2.0, "monotonous light-varied light" 2.1, "hierarchical/level " 2.2, " tenuous/intimately spaced" 2.3 and "cramped-spacious" 2.3.Those found in the seating area were "obviously-mystical/mysterious" at 1.5, "general-identity" 1.5, "hierarchical-level" 1.6, "monotonous light-varied light" 1.7, and "cold-warm" at 1.7.It was discovered that the "obviouslymystical/mysterious" variable had the lowest rating in both areas in addition to the "cold-warm", "monotonous light-varied light", and "level-hierarchical/tiered" variables.Meanwhile, the assessment of meaning in the altar area was observed to be relatively better than in lighting in the congregation seating area which was reported to be monotonous, less meaningful, less identifiable, less sacred, less mystical, and lacked hierarchy.
The variable with the highest score in both areas was found to be "like it-do not like it" with 3.5 in the altar area and 3.0 in the congregation seating area.This showed that respondents relatively liked the interior lighting of the GKN Filadelfia church building.Another similarity was the "complex/crowdedsimple" variable with a score of 3.2 and 3.0 respectively, thereby indicating the feeling of relative simplicity in lighting conditions.There were certain differences in perception of both areas in some cases with the altar area reported to be more "clear" and "beautiful" with 3.2 as well as "sacred" and more "bright" 3.1.Meanwhile, the congregation seating area was found to be more "populist" with 3.2, "not dazzled" 3.0, and "concentrated" 2.9.
Previous research conducted by Intan and Arifin in other church showed that the level of perception of solemnity was predominantly influenced by the quality of natural light entering the auditorium in addition to several other aspects.The absence of regulated natural light in GKN Filadelfia was probably due to the level of solemnity.However, it was possible to form a mystical impression at the altar by providing local lighting with an indirect spotlight from above.The arrangement of this lighting provided the impression of coming from heaven using small, yellow candle lights to create a mystical ambiance in the absence of natural lights, as mentioned by Palealu et al.In GKN Filadelfia, the efforts to achieve a mystical and sacred impression were pursued by dimming the lights in the congregational seating area to allow the congregants to focus on the well-lit altar area and to create an intimate atmosphere in the seating area by limiting distractions.Therefore, the absence of hierarchical lighting contrast between the altar and congregational seating area led to the inability to achieve the mystical, sacred, and solemn atmosphere that could be created by the lights.
Perception of the respondents regarding both areas was observed to be more positive during the evening-night lighting conditions compared to morning-afternoon.However, the patterns generated were relatively similar for the word choices provided despite these differences.

Conclusion
In conclusion, the quantity method applied to measure lighting using a lux meter showed that the intensity was below the required standard but the response from the congregants indicated a contrasting evaluation.The phenomenon showed that quality of lighting does not always have to be based on established standards.This was confirmed by the fact that the respondents felt lighting was relatively bright, clear, not dazzling, had appropriate patterns and colors, and was harmonious and beautiful, even though the quantity was only estimated at 40-50 lux in the congregation seating area and 150 lux in the altar area.
The assessment of the visual conditions was observed to be different from the meaning associated with church space.This was because lighting conditions were considered relatively good for the visual task but unable to meet the expectations needed for the identity, warm, intimate, mystical, hierarchical, and broad atmosphere in church.The visual condition was perceived to be general, cold, tenuous, or distanced, clear, level, and tight.These results showed that the interior lighting of a church needs to be designed to meet the needs of the visual task, fulfill the significance of the function of building as a place of worship and provide a deeper atmosphere.

Figure 1 .
Figure 1.Existing lighting condition inside GKN Filadelfia building

Figure 3 .
Figure 3.The maximum, minimum, and average values of lighting level.

Figure 4 .Figure 5 .
Figure 4. Visual perception of the Altar area

Figure 6 .
Figure 6.The Visual perception of the congregation seating area

Table 1 .
Variables of Perceptual Quality of Lighting in Church