4K resolution may be a convenient description, but around the world, it calls to mind different things. In Japan, 4K resolution tends to be associated with TV broadcasts, while in the U.S., where the Hollywood film industry is located, it may call to mind digital cinema specifications. Even if you know that material will be used for broadcast, requirements vary depending on whether it will be used in a TV program or added to a commercial as graphics. It's important to be aware of these distinctions.
For TV broadcasts, one organization involved in establishing technical standards is ITU-R (International Telecommunication Union Radiocommunication Sector). ITU-R doubled the existing resolution of HDTV broadcasts to establish the 4K resolution of 3840 x 2160. Though it was initially called QFHD (Quad Full HD), in time it generally became known as Ultra HD. Somewhat confusingly, 8K was identified in other ITU-R recommendations as Ultra-high-definition television, which led to the common abbreviation Ultra HDTV. To avoid confusion with this name for 8K, Ultra HD has often been referred to as UHD recently. It should be noted that ITU-R recommendations refer to 4K and 8K resolutions as 4K UHDTV and 8K UHDTV, respectively. Progressive scanning has been adopted, and specifications call for the ITU-R BT.2020 color gamut and frame rates of 30, 50, 60, 100, and 120 Hz. Compatibility with existing frame rates is currently ensured by including support for 29.97, 59.94, and 119.88 Hz in areas where a drop frame is used. Progressive scanning helps maintain the sharpness and clarity of next-generation 4K/8K video, which is not affected by interlacing artifacts (called jaggies) or loss of vertical resolution.
Meanwhile, key digital cinema technical standards have been established by Digital Cinema Initiatives, LLC (DCI). Here, 4K resolution is defined as 4096 x 2160, using multiples of 16 for easier processing. This resolution is known as full 4K. Progressive scanning is used, as is the DCI-P3 color gamut, to suit characteristics of projector light sources. Color depth is 12-bit for RGB colors, and the frame rate is either 24 or 48 fps.
FOR-A products are designed for specific resolutions. FT-ONE series high-speed cameras support full 4K resolution, and other FOR-A products support up to UHD resolution.