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SMPTE RANGE RGB and FULL RANGE RGB basics

The following overview gives a very basic understanding on YUV and RGB conversions. For simplicity sake, we are using 16-235 or 0-255 as the color levels for YUV and RGB. These ranges apply to 8-bit color depth but please note that there are higher color depths (10, 16) that have higher values but similar in range.

YUV and RGB do not traditionally have the same ‘black’ and ‘white’ levels. In 8-bit YUV, black is represented as ‘16’ but in 8-bit RGB black is ‘0’, and 8-bit YUV white is ‘235’ but 8-bit RGB white is ‘255’. Any values under 16 in YUV are considered Super Black and any values over 235 are considered Super White.

Many applications (like Final Cut Pro, Premiere Pro, After Effects) will convert YUV to RGB in such a way that expands and maps the black/white levels of YUV to the black/white levels of RGB, and likewise they will convert RGB to YUV in such a way that contracts and maps the black/white levels of RGB to the black/white levels of YUV. This is considered converting YUV to Full Range RGB (or Computer Range RGB) because the 16-235 values of YUV are expanded and mapped to the Full Range 0-255 of RGB.

While ‘technically’ Super White and Super Black are illegal YUV values, some users do like to preserve them in their workflows and so there are some applications like Sony Vegas and Avid Media Composer that are aware of the color levels differences of YUV and RGB data. These applications allow workflows where YUV can be converted to/from RGB that provides more of a one-to-one mapping of the color levels where 16-235 YUV is converted to 16-235 RGB. This is considered converting YUV to SMPTE Range RGB (or Video Range RGB) because the 16-235 values of YUV are mapped to 16-235 RGB.

Some examples of when applications perform these YUV<->RGB conversions are when
a. Viewing YUV on a computer monitor since computer monitors are RGB
b. Viewing RGB on a broadcast monitor since broadcast monitors are traditionally YUV
c. Performing RGB-based effects on YUV data
d. Converting between different video compression types

Some advantages/disadvantages of using Full Range RGB conversions
a. Full Range RGB is found in more applications especially more ‘non-professional’ applications
b. Since Full Range RGB is more commonly found in applications, viewing Full Range RGB on a computer monitor will not look ‘washed’ out
c. Full Range RGB does not preserve the Super White and Super Black values of YUV

Some advantages/disadvantages of using SMPTE Range RGB conversions
a. SMPTE RGB preserves the Super White and Super Black values of YUV
b. SMPTE RGB may look ‘brighter’ or ‘washed’ out on your computer if Full Range RGB is expected by an application
c. Using SMPTE RGB is more of a complex workflow as usually applications are expecting RGB to be in the Full Range RGB.

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