Aspect Ratios

These are some aspect ratios encountered in various branches of visual engineering. One day, i'd like to draw some diagrams to illustrate how they compare to each other.

Value Name Use Notes
1 square
1.33333333 4:3 TV, computer monitors [4/3]
1.41421356 Lichtenberg Ratio A-series paper sizes [sqrt(2)] If you cut a rectangle with this ratio in half, you're left with two such rectangles.
1.43 IMAX Cinema It's not narrow, it's tall!
1.5 15:10 Semi-widescreen computer monitors (WSXGA) Why?
1.6 16:10 Widescreen computer monitors (WXGA, WSXGA+, WUXGA, QWXGA) Like 16:9, but the numbers come out nicer (1920x1200 rather than 1920x1080 - the latter is what an HDTV is).
1.61803399 Golden Ratio various [(1 + sqrt(5)) / 2] If you take away a square from the end of a golden rectangle, you're left with another. Traditionally considered the most visually pleasing rectangle.
1.7777777 16:9 Widescreen TV [16/9] I'd love to know why this was chosen.
1.85 Widescreen Cinema The standard widescreen format; several others are in use
2.35 CinemaScope Cinema This is the ratio used by CinemaScope Optical, the first super-widescreen format; it was adopted by successor formats, including the current Panavision. This is pretty much the standard super-widescreen format.
2.77 Cinerama + Ultra Panavision 70 Cinema The widest widescreen ever. Cinerama used three cameras or projectors to do it; Ultra Panavision 70 squeezed it onto a single 70 mm reel. Only two films were shot in Ultra Panavision 70: Ben-Hur and Raintree County.

Greg Lovern has written a good explanation of anamorphic widescreen (broken link). The mysterious TV Repair Man has also written a good overview with lots of links. There is lots more information on widescreen cinema formats at Digital Dreams, eFilmCenter and Reel Classics. Brian Fitzgerald has an excellent set of pages on aspect ratios, letterboxing and cinematographic processes. Props to all of the above.