AJA KONA 4 PCI-E Video I/O Card (HDMI Output, Cable Included) - Manual (Page 76)

KONA Capture, Display, Convert v15.5 76 www.aja.com
About 8-bit Versus 10-bit Video
While both 8- and 10-bit uncompressed video are capable of providing excellent
quality broadcast video, 10-bit represents a significantly higher quality and is
preferable in many situations.
Visually, in 8-bit video compared to 10-bit video, you will notice a substantial
difference. In 8-bit video there will be “contour lines” or “striations” visible,
particularly noticeable in scenes having soft gradients like a ramp or sunset. For
example, if a sky region is mostly the same color but varies by only a few digital
numbers from one side of the picture to another, you may see contour lines
where the signal passes from one digital value to the next higher value.
Since each numerical value in a 10-bit system is only one fourth as large as an
8-bit system’s, these contours become invisible and the sky varies smoothly.
10-bit video is often used when the source and output video (or “master”) is also
10-bit. Even if the input and/or output video is 8-bit, a 10-bit “project” will still
maintain a higher quality when there is a significant amount of effects rendering
involved.
About 12-bit Video
With the emergence of High Dynamic Range and Wide Color Gamut video,
support for even more colors became necessary. 12-bit video theoretically has
4x color resolution of 10-bit video, but current video monitor technology cannot
display this full resolution. However, 12-bit video can be useful for postproduction
and color grading purposes, as it allows greater control of subtle colors.
About RGB and YCbCr (YUV) Video
KONA supports both YCbCr (also commonly called YUV) and RGB pixel formats.
Because the KONA (and SMPTE SDI’s) native format is YCbCr, AJA recommends
using a YUV Pixel Format. YUV provides headroom for “superwhite” and
"superblack”, and these video levels will be clipped when transcoding to
RGB. Also, RGB/YUV transcoding involves a level translation that results in
mathematical round-off error.