an aspect ratio of a frame of 35mm film when used with 4-perf pulldown
widescreen
a variety of aspect ratios that are greater than the Academy ratio
letterboxing
the practice of transferring film shot in a widescreen aspect ratio to standard-width video formats while presenting the film's original aspect ratio, the resulting image has mattes (black bars) above and below it (part of the image / signal)
list
1.31:1 - IMAX - 70mm gauge, horizontal projection
1.33:1 (4:3) - 25mm "full frame", analog television
1.34:1 - IMAX - film
1.5:1 (3:2) - APS-C
1.60:1 (16:10) - early widescreen computer displays
1.78:1 (16:9) (wide-screen) - digital television, current widescreen displays