Just watch this excellent documentary “The Changing Shape of Cinema: The History of Aspect Ratio” and you probably have learned everything you need to know about aspect ratio used in cinema and TV.
For my own imaging I’m currently using that classic “Cinemascope” aspect ratio 2.35:1 which is presented in a 16:9 frame so you have that “letter box” look (black region on bottom and top). In some occasions, I’m using an anamorphic lens to get closer to that “cinematic” look and shape.
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