Concept

# 21:9 aspect ratio

Summary
"21:9" ("twenty-one by nine" or "twenty-one to nine") is a consumer electronics (CE) marketing term to describe the ultrawide of 64:27 (2.:1 or 21.:9), designed to show films recorded in CinemaScope and equivalent modern anamorphic formats. The main benefit of this screen aspect ratio is a constant display height when displaying other content with a lesser aspect ratio. The 64:27 aspect ratio of "21:9" is an extension of the existing video aspect ratios 4:3 (SDTV) and 16:9 (HDTV), as it is the third power of 4:3, where 16:9 of traditional HDTV is 4:3 squared. This allows electronic scalers and optical anamorphic lenses to use an easily implementable 4:3 (1.:1) scaling factor. \left(\tfrac{4}{3}\right)^1 = \tfrac{4}{3} = SDTV \left(\tfrac{4}{3}\right)^2 = \tfrac{4}{3} \cdot \tfrac{4}{3} = \tfrac{16}{9} = HDTV \left(\tfrac{4}{3}\right)^3 = \tfrac{4}{3} \cdot \tfrac{4}{3} \cdot \tfrac{4}{3} = \tfrac{64}{27} = "21:9" The term "21:9" was chos
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