Sky Lens was fitted to a whole sky camera, typically used in a pair separated by for stereo imaging, and equipped with a red filter for contrast; in its original form, the lens had a focal length of and cast an image in diameter at 8. Conrad Beck described the camera system in an article published in 1925. At least one has been reconstructed. German and Japanese development In 1932, the German firm Allgemeine Elektricitäts-Gesellschaft AG (AEG) filed for a patent on the Weitwinkelobjektiv (wide-angle lens), a 5-element, 4-group development of the Hill Sky Lens. Compared to the 1923 Hill Sky Lens, the 1932 Weitwinkelobjektiv featured two diverging meniscus elements ahead of the stop and used a cemented achromatic group in the converging section. Miyamoto credits Dr Hans Schulz with the design of the Weitwinkelobjektiv. The basic patented design was produced for cloud recording as a 17 mm 6.3 lens, and the artist known as Umbo used the AEG lens for artistic purposes, with photographs published in a 1937 issue of Volk und Welt. The AEG Weitwinkelobjektiv formed the basis of the later Fish-eye-Nikkor 16 mm 8 lens of 1938, which was used for military and scientific (cloud cover) purposes. Nikon, which had a contract to supply optics to the Imperial Japanese Navy, possibly gained access to the AEG design under the Pact of Steel. After the war, the lens was mated to a medium format camera and was produced in slightly modified form (focal length increased slightly to 16.3 mm) as the "Sky-image Recording Camera" in March 1957 for the Japanese government, followed by a commercial release as the Nikon Fisheye Camera (also known as the "Nikon Sky Camera" or "Nikon Cloud Camera") in September 1960, which had a retail price of . The revised lens created a circular image in diameter and covered a complete hemispherical field of 180°. Only 30 examples of the Nikon Fisheye Camera were manufactured, and of those, 18 were sold to customers, mainly in the United States; Nikon likely destroyed the remaining stock to avoid tax penalties. A photograph of pole vaulter Bob Gutowski taken by the Fisheye Camera was published in Life in 1957. Also in 1938, Robert Richter of Carl Zeiss AG patented the 6-element, 5-group Pleon lens, which was used for aerial surveillance during World War II. The converging rear group of the Pleon was symmetrical, reminiscent of the 4-element