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FCP Video Waveform Accuracy

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Tom Tomlinson
FCP Video Waveform Accuracy
on Mar 6, 2010 at 4:18:07 am

While I'm still trying to wrap my head around quicktimes and gamma differences between rgb Qt's and 422 Qt's---there is still something I see & I don't understand.

If I convert my RGB QT which has a 32 step grey chart to 10Bit 422 Uncompressed QT. How come FCP & QT's viewer only displays the 0-100 range yet the scopes show all the steps (3 above 100).

In Shake & Nuke-I only see 0-100 on the waveform/histograms.

Why do the scopes show this?

thanks for any thoughts,

Tom

Tom Tomlinson
Telecine Ass't.
NYC


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Rafael Amador
Re: FCP Video Waveform Accuracy
on Mar 6, 2010 at 2:57:18 pm

Google the article of Nattress "Video Levels in Final Cut Pro".
Shake, and I guess NUKE too, works in RGB. No way for values over 100%.
Rafael


http://www.nagavideo.com


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Tom Tomlinson
Re: FCP Video Waveform Accuracy
on Mar 6, 2010 at 6:12:32 pm

Thanks Rafael. I did find that. Its a great find.

But what I find odd is that if the original 33 step rgb chart got converted to 422 and clipped. What I see on the viewers are the middle 29 steps. What I see in the histogram/waveforms of shake & nuke is 29 steps. But what I see in fcp's viewer only displays 29 steps but the fcp waveform shows 33 steps from -10 to 110.

So does qt & FCP block that extra info--basically "proc it" but the waveform is "pre-proc amp"?

thanks,
Tom




Tom Tomlinson
Telecine Ass't.
NYC


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Rafael Amador
Re: FCP Video Waveform Accuracy
on Mar 7, 2010 at 2:20:52 am

Hi Tom,
Can you tell me the specs of the file of the original chart?
If you are getting these "off-specs" values, your chart must be, at least, 10b RGB.
8b RGB doesn't let you pass nothing over 100% or below 0%.


[Tom Tomlinson] " But what I see in fcp's viewer only displays 29 steps but the fcp waveform shows 33 steps from -10 to 110. "
This indicates that there are some super-whites and super blacks.
In the Canvas, you can not tell Super-whites from whites. They look the same: White.
Same happens with Blacks and Super-blacks.
In the Canvas they look just like black, but the Videoscope can see the difference.
Rafael



http://www.nagavideo.com


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Tom Tomlinson
Re: FCP Video Waveform Accuracy
on Mar 7, 2010 at 3:29:02 am

Its a dpx sequence that I rendered from baselight color correction. I rendered a 10 bit 422 uncompressed qt and an 8 bit one.

They both display clipped white on the viewer yet on fcp waveform/parade they are not clipped and show 33 steps.

I am trying to get a solution for color accurate 422 Quicktimes from color corrected rgb dpx files to satisfy client deliverables.

Tom



Tom Tomlinson
Telecine Ass't.
NYC


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Rafael Amador
Re: FCP Video Waveform Accuracy
on Mar 7, 2010 at 5:03:03 am

[Tom Tomlinson] "They both display clipped white on the viewer yet on fcp waveform/parade they are not clipped and show 33 steps. "
I guess this is due to a shortcoming in QT/FC on displaying.
The display is done in 8b RGB, so you get the clipping, however the clipping doesn't happens on exporting.
I had this issue (drove me nuts for a few days) when applying certain filters (NeatVideo). SuperWhites are slashed in Viewer and Canvas (and even in the Videoscope) but are preserved on exporting.
Trust the Videoscope.
Rafael
PS: This is not a question for the FC Basic Forum.




http://www.nagavideo.com


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