To film the mosaics of Hagia Sophia in situ, the Byzantine Institute photographer Pierre Iskender experimented with different techniques to expose the film to more light, including open aperture on the camera lens, artificial and natural lights, half and full speeds, and different types of film.
Notebook entries from the years 1936-1940 document the technical decisions made during the filming of the mosaics in the Hagia Sophia - see the EXHIBIT ITEMS below. From several entries we can assume that Iskender was also asked to operate the film camera. In the beginning, he experimented until he formed a clear idea of the light conditions and the speed that would work best. Then, he filmed the same subject several times with different settings: at half speed and full speed, with artificial lights and with natural light. The results were significantly different each time, thus allowing Iskender to determine the ideal settings and, as a side effect, giving the Byzantine Institute a tool to explore the characteristics of the mosaics and their differing appearance according to changing light situations. In general, Iskender used a wide open aperture, due to the fact that the mosaics are located in areas that were quite dark. Today, visitors to Hagia Sophia will find these same mosaics unnaturally illuminated by spot lights, which obscures the natural reflection and play of light across the surface of the mosaics.
Iskender seems to have attempted to capture both moments of maximum detail and of maximum veracity. The difficulties of this process can be observed in the detailed notes and calculations that were taken by Richard and William John Gregory, who acted as assistants to Iskender during the filming. Some notebook entries document that special lighting systems were installed and others detail their exact brand and voltage. By 1940, the process of making color motion picture films had been perfected by creating almost studio-like "dark room" conditions, which were employed in the North Tympanum. Iskender used 16 mm Kodachrome film for the moving images. This required him to stay up-to-date with the requirements of the equipment, which not only included the film stock itself, but also special lights. Kodak would issue instructions for every film and its specific usage and light conditions. Sometimes, this meant that planned filming was postponed due to mismatched equipment or missing adapters.