There are 5 common ratios: 4:3 (1.33:1), 3:2 (1.5:1), 16:9 (1.78:1), 1.85:1, 2.35:1
In still camera photography, the most common aspect ratios are 4:3, 3:2, and more recently being found in consumer cameras 16:9. Other aspect ratios, such as 5:4, 6:7, and 1:1, are used in photography as well.
The most common aspect ratios used today in the presentation of films in movie theaters are 1.85:1 and 2.39:1. Two common videographic aspect ratios are 4:3, the universal video format of the 20th century and ; 16:9, universal for high-definition television and European digital television.
Why is this an issue? When I am creating my art I’m not working on a fixed canvas but just points in space. And all I’m really doing is cropping my view by setting the screen “aperture” to whatever I choose. When I’m done, I render the image into a digital file format (jpg, png, bmp) so that it can be displayed or printed, at any ratio. So I have to chose and sometimes the choices of the various standard paper sizes are not optimal for the image. Worse is if I want two different ratios then it’s two separate renderings (5-12+ hours) because it is not possible to scale/re-size one into another without significant cropping.