The Blu-Ray is 16:9. There is no open matte version of Interstellar. The film was shot on 35mm anamorphic (2.35:1) and IMAX 65mm (1.43:1). The Bluray emulates the IMAX experience by switching between full 2.40:1 and 1.78:1 (cropped vertically from 1.43:1). The DVD is constant 2.40:1.
Thought I saw a 1.43:1 IMAX frame that on the BD is 2.35/2.40:1, has anyone else noticed this?