The Boston Camera, also known as Pie Face and officially classified as the K-42 Camera Model, was a prototype airborne photo reconnaissance camera manufactured for the United States Air Force by Boston University in 1951 and tested on the Convair B-36 and the C-97 Stratofreighter. The model carried on the first ERB-36D (44-92088) had a 6,096-millimetre (240.0 in) focal length, which was achieved using a series of lenses and mirrors. The lens had an f/8 stop and used a 1/400 second shutter speed, and could photograph a golf ball from an altitude of 45,000 feet (14,000 m). The camera used 18-by-36-inch (46 by 91 cm) negatives. The camera was installed aboard Boeing C-97A 49-2592 installation and serial number citation needed(not an "RC-97" or "EC-97" as often widely quoted) which was used op