Where to Get 4K Video
In July of 2010, YouTube announced the 4K video support with a resolution of 4096 x 3072. Presently, thousands of videos with 4K resolution can be watched on YouTube.
Official examples of videos are available in the 4K Resolution playlist. It’s also possible find such videos by queries like "4K Resolution", "4K" or "4096p". The latter is not terminologically correct since the indications of 480p, 720p, 1080p refer to the vertical resolution. Regardless, a portion of 4K resolution videos is still uploaded under this tag.
In the middle of the 2000s, 4K digital cameras appeared on the market. The first available device for sale was the Dalsa Origin camera of Canadian Dalsa Corporation Company. It could make the video with the resolution of 4096 x 2048 in 16-bit RAW-format. This format conveys a very high dynamic range. Before that, digital camera color format was within 8, 10, or 12 bit. Dalsa Origin camera records video on an off-site storage with a speed of 400 MByte/sec.
In 2007, Red Digital Cinema Camera Company released a Red One camera. The camera had 12-megapixel CMOS-sensor and made the video with a resolution of 4096 x 2304, and the speed was 30 fps. At the beginning of 2011, the company presented a Red Epic camera with a 14-megapixel sensor and a resolution of 5120 x 2700.
Digital single-lens reflex camera (DSLR)
Many up-to-date DSLR-cameras, even non-professional ones, make 1920 x 1080 resolution video while having the sensor with the resolution of over 12 megapixels. For instance, the Nikon D3100 camera makes photos with a resolution of 4608 x 3072, and a sensor of Canon EOS 550D camera has a resolution of 5184 x 3456.
Thanks to the methods described on specialized forums, it’s possible to create a 4K video made by a fast shooting on similar cameras, such as Nikon D3s. Examples of such videos can be found on YouTube.