Legal chroma levels for going out to broadcast

[Chris Clementson]

“it’s possible to have very slight out-of-gamut issues that are technically correct according to conventional scopes.”

Can you give an example of this using 8-bit values?

Interesting that they have two flavors of NTSC (with and without setup) and two flavors of EBU, but no ATSC and no filter specifically for BT.709.

[Marc Wielage]

[Chris Clementson] “Can you give an example of this using 8-bit values?”
No, this is strictly going by the (rare) rejections I get from QC people. In some cases, I can BARELY see a bit of chroma hitting the GxB or GxR channel plot (similar to the Tektronix Diamond scope), but it’s so subtle that it’s almost impossible to really see. There are automated QC programs like Tektronix Cerify that do this as a matter of course:

https://www.tek.com/file-based-qc/cerify-video-content-analysis

This kind of thing is beyond the scope of most colorists, but my tactic is just to try to use good judgement and kick in the Resolve Gamut Mapping plug in when I suspect we’re straying within a few percentages of being illegal. Colored neon or very bright car tail-lights are big offenders.

[Chris Clementson]

BT.709 calls for chroma 16 – 240 and luma 16-235.

I can’t imagine anything else pushing you close to the speed limit.