As with "Shinano"s half-sisters and , the new ship's existence was kept a closely guarded secret. A tall fence was erected on three sides of the graving dock, and those working on the conversion were confined to the yard compound. Serious punishment—up to and including death—awaited any worker who mentioned the new ship. As a result, "Shinano" was the only major warship built in the 20th century to have avoided being officially photographed during its construction. The ship is only known to have been photographed twice: on 1 November 1944, by a Boeing B-29 Superfortress reconnaissance aircraft from an altitude of , and ten days later, by a civilian photographer aboard a harbor tug during "Shinano"s initial sea trials in Tokyo Bay.