Sony FX 6 Quick Start Manual page 48

Image Resolutions: three options
1. 4K UHD 3840 x 1080 is the 4K broadcast/web standard. The aspect ratio is
16:9, the same as HD video.
2. 4K DCI 4096 x 2160 is only for cinema. The aspect ratio is 17:9. Web versions
will have to be cropped or pillar-boxed.
3. HD 1920 x 1080 is the HD broadcast/web standard.
Keep in mind that all displays (screens, projectors) in the EV depot are HD.
There are NO 4K displays. There are no HDR displays.
You can shoot in 4K UHD and output a HD version because the aspect ratio is
the same: 16:9. But only shoot 4K if you know (hope) that the project will one
day be displayed in 4K. For a class assignment, just shoot HD unless your
professor demands 4K as 4K generates significantly larger file sizes.