New views: LED lighting technology for St. Peter's Basilica in the Vatican

Even if since 1990 St. Peter's Basilica in the Vatican is no longer the world's largest church – the new Roman Catholic church in Yamoussoukro, Ivory Coast, which is modelled on St. Peter's, is larger – this work of numerous masters of the Baroque and High Renaissance is still of great importance, and not only because of its function as one of the six papal basilica maiores. Until the end of last year, the magnificent interior was still being viewed with the aid of gas discharge lamps. Now more than 780 special LED lights inside St. Peter's Basilica provide uniform illumination and higher spectral quality with considerably lower energy consumption.

Newly-perceptible architecture
"Before you could only glimpse the beauty of the architecture in St. Peter's Basilica. Today you can appreciate it in full." At the official inauguration, Cardinal Angelo Comastri, director of the cathedral workshop since 2005, praised the "ingenious, intelligent and scientifically-positioned lighting" in St. Peter's Basilica.
Around 100,000 light-emitting diodes developed and produced by the Munich-based company Osram in Wipperfürth, North Rhine-Westphalia, are responsible for the new reading light. The LED luminaires and light strips are integrated into the architecture as invisibly as possible, while upward-facing spotlights illuminate the ceilings opposite. This prevents shadows from being cast by the stucco and decorative elements. The marble floor, which is illuminated by downward directed spots, also remains shadow-free. Thus, glare-free lighting is not only guaranteed in the altar area.

Features of modern lighting technology
The LED technology used means that some parts of the basilica are now ten times brighter than before. This in turn allows some totally new views of the domes in the aisles hitherto hidden to even long-standing employees and art historians. With a CRI value of around 95, the LEDs have been set for optimum colour rendering, which could otherwise only be achieved in the artificial range using incandescent lamps. However, the new technology is known to have one decisive advantage: According to the Vatican's own figures, energy consumption is reduced by up to 90% compared to the previous lighting technology. The new splendour revealed by the lighting can also be appreciated from afar: Thanks to the newly-created brightness, 4K and 8K UHD digital TV recordings and transmissions from the dome are now possible.

Digitalisation played a decisive role in the project as a whole, explains Dr. Thorsten Müller, head of innovation and research at Osram. On the one hand, the system installation was digitally planned using virtual light simulations. This meant that the lighting concept could be developed independently of the building and with as little impact on the basilica as possible. In addition, the lighting control system is also digital. The lighting scenarios for specific occasions can be set and activated via DALI and DMX using computer- and manufacturer-independent mobile terminals. The new LED lighting seems almost a milestone in the history of this centuries-old sacred building.

Masterly co-production
St. Peter's Basilica in its present form is not only remarkable for the popularity and large number of its builders. Construction of the basilica began in 1506 on Vatican Hill outside the gates of Rome, with the new church taking the place of the Old St. Peter's Basilica. The basilica was initially designed by Bramante as a strictly symmetrical central structure. 43 years after the laying of the foundation stone, Michelangelo Buonarroti took up the basic form in his design and merged the central area, crowned by his monumental dome which has survived to this day, with the side chapels to form a single unit and added an entrance hall. Other master builders, including Raphael and Giuliano da Sangallo, wanted a longitudinal building, which was finally realised under the direction of Carlo Maderno from 1607 onwards. The oversized facade, which ends at St. Peter's Square, is also the work of the latter. The front of the basilica and the immense square lined with colonnades was completed in 1626 under the supervision of Gianlorenzo Bernini. A large number of other master builders were ultimately involved in this prestigious project.

"The best light source is invisible" – Osram and the Vatican
The German technology company has also recently upgraded the illumination of Bernini's colonnades. In autumn 2016, the new lighting system for St Peter's Square, which covers an area of 48,000m2 and can simultaneously accommodate up to 400,000 visitors, was inaugurated. Here, too, floodlights have been unobtrusively integrated into the built structure and can create numerous preset scenarios ranging from strolling light to lighting for major events. The new lighting concept was not only to reduce energy consumption but also light emissions, and the collaboration with Osram took several years. Since the end of 2014, the Sistine Chapel has been bathed in light produced by specially-developed LED luminaires. During this first order for the Vatican, the company impressed its client with its technologically-precise custom work. Over a planning period lasting several years, exposition tests were carried out with colour pigments typical of the famous frescoes. This resulted in luminaires that produce an art-conserving, colourfast light with much higher illuminance than previous halogen lamps. The last joint project to be completed before work began in St. Peter's Basilica was completed in June 2017. This involved the invisible integration of LEDs into the Raphael Rooms in the Vatican Museum. The world-famous wall and ceiling paintings located here have as a result also experienced a visual renaissance. Moreover, one of the most prominent master builders and art decorators of St. Peter's Basilica can now be seen in new, resplendent colours: In Raphael's "School of Athens", the figure of Heraclitus is depicted in the foreground of the painting by a portrait of Michelangelo.