This is what 1920x1080 looks like in a 28K 3:1 aspect field:
If you click on the image above it won't fit on a 30" Apple Cinema Display. And it's 1/8 res.
An 8-bit 28,000 x 9,334 image would be roughly 748 megabytes in Photoshop.
This isn't an imager size that RED made up, it's used in crazy panoramic cameras.