Personally I've never understood the 2.39:1 aspect ratio. My TV, computer monitors, laptop and phone are all 16:9. TV shows I watch are 16:9 as well. Other than 4:3, it seems like the universal ratio. So why are movies shot at 2.39:1, a ratio that causes black bars on any device you watch it on?
Because 16:9 wouldn't exist except for the existing theater ratio of 2.39:1. 16:9 is a compromise between existing movies and academy ratio[1]. 21:9 would have been a better ratio, but we got the compromise just like the resolution is 1920 x 1080 instead of something that jived better with computers.
If you shoot a movie in 16:9 it will look cropped when viewed in a theater.
1) there is a YouTube video that explains it. I think it made HN a while ago.
