4K resolution
As noted above, DCI 4K is 40962160, while 4K UHD is 38402160, producing a slight difference in aspect ratio rather than a significant difference in resolution. Traditional displays, such as LCD or OLED, are 3840 pixels across the screen, with each pixel being 1/3840th of the screen width. They do not overlap—if they did, they would suffer reduced detail. The diameter of each pixel is basically 1/3840th of the screen width or 1/2160th of the screen height - either gives the same size pixel. That 38402160 works out to 8.3 megapixels, the official resolution of 4K UHD (and therefore Blu-ray UHD discs).
Da Vinci Systems
The da Vinci 2K Color Corrector, manufactured starting in 1998, was a completely revised color correction system that supported HDTV, SDTV, and 2K formats. The later system, the 2K Plus with improved color corrector tools was used on high-end DataCines and telecines like Thomson-Grass Valley's Spirit Datacine and Cintel's C-Reality & ITK Millennium. The 2K operated with a 4:2:2, 4:4:4 or 8:4:4 input in NTSC or Pal. In HDTV it operated with either 4:2:2 or 4:4:4 inputs. Many were interfaced to the Spirit DataCine.