hands while taking aim. In 1953 Ray-Ban introduced G-15 tempered glass lenses. These neutral gray/green lenses transmit 15% of incoming visible light whilst providing 'true' color and contrast distribution. Military type HGU-4/P aviator sunglasses In 1958, American Optical created the Flight Goggle 58 according to the then-new U.S. Air Force Type HGU-4/P aviator sunglasses standard. Type HGU-4/P sunglasses feature semi-rectangular lenses with less lens surface area and are lighter compared to the preceding Type G-2 sunglasses. The HGU-4/P design frame allowed the visor to reliably clear the aviator's spectacles when a flight helmet is worn, and covers the full field of vision. The frame additionally features bayonet temples designed to slip under a flight helmet or other headgear and were more compatible with oxygen masks. They are commercially known as "Original Pilot Sunglass", and were issued by the U.S. military since 1959 to pilots shortly after the HGU4/P was officially recommended by military optometrists in November 1958. The HGU-4/P design frame is also issued to military personnel that require various corrective clear or other type of lenses and allows corrected vision through the full field of vision. Besides the military, Type HGU-4/P aviator sunglasses were also issued to and used by NASA astronauts. By 1982, Randolph Engineering had become the prime contractor for military-style Type HGU-4/P aviation flight glasses for the United States Department of Defense. They are commercially known as "Randolph Aviator" sunglasses. HGU-4/P aviation flight glasses are still built to the guidelines of the MIL-S-25948 military specification, a document detailing the manufacturing specifications. One of the many specifications is that the neutral grey lenses used in Type HGU-4/P aviator sunglasses must transmit between 12% to 18% of incoming visible daylight whilst providing 'true' color and contrast distribution. The military HGU-4/P Aviator and the Modified HGU-4/P Apache spectacles intended for Apache attack helicopter aircrew are under regular review to determine their functionality. Gallery References Sunglasses Aircrew clothing Air force uniforms Militaria Aviation mass media 1960s fashion 1970s fashion 1980s fashion 1990s fashion 2000s fashion 2010s fashion