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[TIG] Re: WhaT is LegaL?


May I say that chrominance over-induldgence is a rampant plauge throughout
the land and must held in check.   Enough for the dramatics.

Seriously, bt had the right idea with "broadcastability" being the starting
point.  Beyond that one may deviate as the rules of their particular game

The confusion may be the actual measurement method ( i.e. vector/wfm), and
what is the tolerence.   On a waveform, we limit luminance excursions to
+103 units and zero (composite) and on the vectorscope ( at  75%) major chroma
excursions inside the outer rose, allowing minor transient excursions
somewhat beyond that.  Even this sounds a bit vauge, doesn't it.  Is there a
rule of thumb?  Folklore?   Do engineers and colorists (and assistants)
watch closely enough and do we all agree on what will be tolerated?  

If I create legal but highly saturated colors in component (YUV) space will
it reproduce correctly when encoded?  What will it look like, aestetically?
Will my client see something different over the air than what they saw in
transfer when colors flew wild in that rich, red/green/blue/azure canvas of
my monitor?  

Legal gamut and broadcastability are indeed two separate issues but closely
related.  For example what may be perfectly illegal in a given color space
may be perfectly broadcastable in another (and visa vie, of course).

Does anyone, on a regular or selective basis use the RGB legal limit
available in DUI/8:8:8? We have found that, while not perfect or always
appropriate, will definately impose reasonable, (and most often) delicate
compression in the color product, yet without imposing upon the artisitc
intent.  Perhaps Andy Sackheim could comment on whether or not RGB limiting
in 8:8:8 is a desirable attribute in this box.