On the other hand, other image formats having about four
thousands horizontal pixels have appeared from broadcasting
fields. They are called quad HD (QHD). Its horizontal pixel
counts are double HD, and its vertical pixel counts are also
double HD. Since HD has 1920 horizontal pixels and 1080
vertical pixels, QHD has 3840 horizontal pixels and 2160
vertical pixels. QHD doesn’t have any uniquely specified
frame rate, pixel depth per color, and colorimetry reflecting the
existing different broadcasting specifications.
In addition, 4K variants are gradually spreading. 4K
variants are the images that don’t satisfy any technical standard.
One reason is image sensors. For example, image sensors
implemented in digital cinematography cameras have different
aspect ratios from DCI 4K or QHD. The background of this
implementation design is digital post-production process. The
more pixels on original captured images, the better images can
be produced even after the post-production process. Second
reason is graphics editing programs such as Adobe Photoshop.
The image creators who are not familiar with DCI 4K or QHD
technical specifications can easily create out of the
specifications images using those programs. In July 2010,
YouTube announced the support of 4K. It has 4096 horizontal
pixels and 2304 vertical pixels. This image format is also 4K
variants.