Saturation with luminance in waveform window

[Rafael Amador]

Hi Stephen,
No.
The “Chroma Envelop” can reach (depending of the specs of the system) until a 33% more, so 133 IRE.
The problem is that the FCs VideoScope doesn’t let you see the signal that high.
The term “Saturation” shouldn’t be used here.
The truth is that what we see in “Saturation” mode is a representation of the Composite signal: Luma + Chroma.
You need to know the specs for delivery ad use an external Waveform or use the Broadcast Safe filter.
Think that you need to get legal four different things:
– Luma
– Chroma
– Composite signal
– RGB
You must be aware of the Excess Luma and Excess Chroma.
Although you should know that the “Excess Chroma” is not such a “”excess of Chroma” but that the Composite signal (Saturation?) is too high.
You can prove this easily: take any picture with “Chroma Excess” and low the Luminance.
The picture will stop to show the “Chroma Excess”. This makes no sense.

Rafael

http://www.nagavideo.com

[Stephen De vere]

Rafael,

Thanks for your reply.

It seems the Broadcast Safe filter is the only tool that might ensure legal levels (assuming it is given correct settings) but I had read that it is not reliable – that it gives different results before and after full timeline rendering.

I prefer manual control and I was hoping to achieve safe levels shot-by-shot using the vectorscope and waveform windows.

So really, only professional external hardware will do a proper legal levels job ?

IS FCP 7 any more ‘mature’ in this respect ?

[Stephen De vere]

I also find that Broadcast Safe filter truncates the bits in the entire image – so worried I lose quality (the source camera files are 8-bit DVCPro50 but I am using a 10-bit uncompressed timeline for the finishing). The same happens with the 3-way Color Corrector but the 1-way Color Corrector filter is fine so I am using that.

Is there anywhere on the net a history/list of FCP versions and their problems and the plugins available to fix ?

OK, sorry, I just found a recent post on this subject
“Does (Broadcast Safe) filter order matter?” that goes into it all.

[Rafael Amador]

Hi Stephen,
The broadcast safe should be applied to avoid any any peak that you may miss after a proper manual-clip-by-clip-frame-by-frame CC.
The BS filter needs to be adjusted as well.
If you use the presets without knowing what are you doing, you may be clipping unncessarilly, or you may be letting pass illegal values.
Yo saw the presets that are: Extremely Conservative, Very Conservative..those for sure will clip more than needed.
The truth is that the BR filter from FC could make a better clipping than the one in Color.
You can do a perfect manual control with the “Proc Amp”. You can control Pedestal, Luma and Chroma.
The problem again is how to monitor this.
Any professional Waveform monitor shows some 140IRE. In FC, 110.
However, if the Luma is below 100% and the full “Saturation” doesn’t reach these 110% everything should be absolutely legal. This would be what you would get with the “Very Conservative” setting of the BS filter, or the default setting in Color.
The “Normal” preset would need a window of 120IRE.
About the CC filter (no 3W-CC, not sure if can works in 10b YUV.
The 3W-CC does for sure.
Rafael

http://www.nagavideo.com

[Stephen De vere]

Rafeal,

So the bit-trunkating (severe ‘combing’) I see in the Histogram, caused by the 3-way CC and B’Safe filters, I should not worry about ? That would be extremely difficult to accept.

I have to say I cannot see the loss in the broadcast monitor.

Beginning to feel I wish I went back to Avid – even the low end version handles this so much more professionally. Their BSafe filter gives control of Composite in addition to Chroma, Luma, RGB.

[Rafael Amador]

Are you editing DVCPro50 in a 10b Unc sequence?
Did you set “Render in High Precision”?
Rafael

http://www.nagavideo.com

[Stephen De vere]

Yes.
Shot and captured full res DVCPro50
Apple 10-bit UC sequence (just now for the finishing)
Render in 10-bit high YUV

I just tried switching to Blackmagic 10-bit UC but same result.

I also downloaded the free Grading Sweet Legalise filter, but it won’t run (FXScript Error) – must be not compatible with my FCP 4.5

[Rafael Amador]

The histogram probably would be the part of the Scope that I would trust the less.
Apple have been fine tuning the Waveform a long the time because have been many complains.
I’ve never herd of nobody complaining of the Histogram. People don’t use it.
I would care of a severe combing in a 10b gradient.
FC have many problems for displaying in 10b. There are filters (Colorista, Neatvideo) that slash the signal in preview, but this doesn’t happens on render.
However I’ve never seen this with the 3W-CC.
Also I have never seen any clipping in that filter.
The Broadcast Safe normally compress part of the signal and clips the rest. That is how it works.
You should make some tests and see the picture after export. You can have a look to the picture in Color.
Also you can use Color just to legalize the full movie.
However Color will also clip if have to do it.
Rafael

http://www.nagavideo.com

[Stephen De vere]

By playing around I’ve narrowed the problem down within the Broadcast Safe filter to the ‘Saturation Limiting’ control.

‘Luminance Limiting’ seems to not have the effect.

Also tried changing sequence codec to 8-bit UC, but same results.

I can now notice the gaps are in the waveform graph too, when applying these apparently damaging filters.

Are you able to reproduce this effect in your setup Rafael ?

[Stephen De vere]

Thanks Rafael I think you have got me onto the right track to solve this – I did an export/import test, (remembering not to use Quicktime Conversion which is well known to be buggy also) and the truncating problem showing in scopes is removed.

So it is some aspect of the still frame render preview. I will look at all those settings too.

I guess I must export the 53 minutes self-contained and then re-import to play out to tape.

Is there a list of ‘gotchas’ anywhere on the www ?