According to the specifications the following aspect ratios for DCPs are valid:
The pixel array size and frame rate shall be one of the formats listed in the table below:
2K Scope (2.39:1) Resolution: 2048×858 FPS:24/1 or 48/1
2K Flat (1.85:1) Resolution: 1998×1080 FPS:24/1 or 48/1
2K Full (1.90:1) Resolution: 2048×1080 FPS:24/1 or 48/1
4K Scope (2.39:1) Resolution: 4096×1716 FPS:24/1
4K Flat (1.85:1) Resolution: 3996×2160 FPS:24/1
4K Full (1.90:1) Resolution: 4096×2160 FPS:24/1
Stereoscopic picture essence tracks shall be limited to the 2K formats, and shall have a frame rate of 48/1 and an edit rate equal to half the frame rate.