256 pixels separates the Cinema 4K and 4K UHD. A difference that TV manufacturers are careful to highlight …
4K in televisions and 4K in cameras: high definition HD and Full HD “4K”. But behind this acronym actually hide two standards to the different definition . The image stamped “4K” televisions is not, as its name suggests, equivalent to broadcast 4K cinema.
The 4K Cinema, the “real thing”
The used 4K cinema, normalized by the DCI ( Digital Cinema Initiatives ), is a bit “true” 4K, that is to say, the horizontal resolution is really to 4 thousand points – 4096 horizontal dots by 2160 dots vertical (denoted “4096 x 2160”). This ratio of about 17/9 is more panoramic than the classic 16/9, which sticks to the film requirements.Moreover, to reproduce Cinema scope standard inherited from the days of film, some directors even reframe a bit in the vertical resolution to display 4096 x 1714 points, a ratio of 2.39 / 1.
Standard or cropped Cinemascope, the image original 4K movies can not be displayed the same way on our consumer equipment that lacks some horizontal pixels …
The 4K TV: Ultra HD
The public displays branded ” 4K ” have a definition of 3840 x 2160 dots, whose real name is Ultra HD (UHD). If the vertical resolution is identical to the movie version, the horizontal resolution is less than of no less than 256 pixels. This lack has to be compensated by cropping the image to production or with black bands on the screen.
The choice not to stick to the original 4K resolution is not a matter of quarrel with the film industry but an industrial choice. Indeed, the definition of 3840 x 2160 dots is exactly twice the vertical and horizontal of the previous generation, Full HD (1920 x 1080 points). By simply doubling the number of pixels in the same ratio slabs, manufacturers have had to evolve their industrial apparatus, rather than investing in new machinery, which would cost them much more. Consumer side, this “simple” pixel doubling was easier to manage both hardware point software – upscaling Blu-ray, video editing software, etc.
Making a difference: Cinema 4K and 4K UHD
The 256 pixels difference between 4K and Ultra HD are not a scandal since it is properly called each of the two standards. Unfortunately for purists, the aggressive marketing of certain brands has already wreaked havoc and the term ” 4K ” has become almost everywhere. 4K is four times 1080p Full HD (sounds amazing?).
That’s why we use 4K Cinema for the “true” 4K (4096 x 2160 points) and 4K UHD for Ultra HD (3840 x 2160 points) of our televisions. You have been warned!