16:9
16:9 (1.77:1) (16:9 = 42:32) is an aspect ratio with a width of 16 units and height of 9. Since 2009 it has become the most common aspect ratio for televisions and computer monitors, and is also the international standard format of HDTV, Full HD, non-HD digital television and analog widescreen television. It is also used inversely (9:16) as the ratio for mobile phone screens. This has replaced the old 4:3 aspect ratio.
Dr. Kerns H. Powers, a member of the SMPTE Working Group on High-Definition Electronic Production, first proposed the 16:9 (1.77:1) aspect ratio at a time when nobody was creating 16:9 videos. The popular choices in 1980 were: 1.33:1 (based on television standard's ratio at the time), 1.66:1 (the European "flat" ratio), 1.85:1 (the American "flat" ratio), 2.20:1 (the ratio of 70 mm films and Panavision) and 2.39:1 (the CinemaScope ratio for anamorphic widescreen films).
Powers cut out rectangles with equal areas, shaped to match each of the popular aspect ratios. When overlapped with their center points aligned, he found that all of those aspect ratio rectangles fit within an outer rectangle with an aspect ratio of 1.77:1 and all of them also covered a smaller common inner rectangle with the same aspect ratio 1.77:1. The value found by Powers is exactly the geometric mean of the extreme aspect ratios, 4:3 (1.33:1) and 2.35:1, √47/15 ≈ 1.770 which is coincidentally close to 16:9 (1.77:1). Applying the same geometric mean technique to 16:9 and 4:3 yields the 14:9 aspect ratio, which is likewise used as a compromise between these ratios.
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