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Why is the Davinci Resolve waveform monitor measuring from 0 - 1023?


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#1 Evan Richards

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Posted 03 November 2017 - 03:00 PM

I thought waveform measured IRE and I thought IRE was measured from -40 to 120. Whats the deal? What does that number represent? What scale is it using to measure?

 

Thanks!


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#2 Tyler Purcell

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Posted 03 November 2017 - 04:05 PM

Stolen from the internet. 

 

In order to get a resulting clip with a range between 0 and 1023, a 10 bits video format needs to be selected as the transcode's format.

 

In YCC 709 (itu.709 is the norm for HD televisions, except some very very old ones that followed SMPTE 240), black is mapped to 16/64 and white to 235/940 in 8/10 bits. Values below 64 (10 bits) are called super black and above 940 super white. The "super" colors are mainly used for color correction as they won't be noticeable on the television."

 

So, It makes me think about the DV waveform scale: This would mean legal video should be kept inside 64-940 range?

Also, I read the top and bottom 5 points of the 0-1023 10-bit scale are reserved for data only, no Image data is recorded... This would be true for the DV WFM scale?


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#3 Bruce Greene

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Posted 04 November 2017 - 11:11 AM

Generally when you work in Resolve, you're grading in full range data.  In a 10 bit file, the whitest white is 1023 and the blackest black is zero.  This is reflected on the waveform.  If you output to "video levels", or 64-940, the transform from full range to video levels will be done upon rendering.  If you need video levels for your display, it is a selection in the preferences.

 

So one can view the waveform as normal. 

 

If you are grading in LOG and outputting LOG for a filmout, then things could be different as one would be grading viewing through a film emulation LUT, and the scopes would be showing a LOG image. If I remember correctly, film white was around 800 and blacks 125, but I really don't remember.  But, today, who grades solely for a film out?  I haven't made a grade for filmout since 2011.  My last filmout was done in 2013 and we graded for DCP and converted that version to LOG for a filmout with some adjustments made to the conversion to make a nice negative.

 

So Evan, nothing to see here.  Go back to work :)


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#4 Evan Richards

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Posted 04 November 2017 - 11:25 AM

Stolen from the internet. 

 

In order to get a resulting clip with a range between 0 and 1023, a 10 bits video format needs to be selected as the transcode's format.

 

In YCC 709 (itu.709 is the norm for HD televisions, except some very very old ones that followed SMPTE 240), black is mapped to 16/64 and white to 235/940 in 8/10 bits. Values below 64 (10 bits) are called super black and above 940 super white. The "super" colors are mainly used for color correction as they won't be noticeable on the television."

 

So, It makes me think about the DV waveform scale: This would mean legal video should be kept inside 64-940 range?

Also, I read the top and bottom 5 points of the 0-1023 10-bit scale are reserved for data only, no Image data is recorded... This would be true for the DV WFM scale?

OK. That makes sense. Do other applications or monitors measure it that way? I've never seen it measured on that scale before.

Thanks!


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#5 Evan Richards

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Posted 04 November 2017 - 11:28 AM

Generally when you work in Resolve, you're grading in full range data.  In a 10 bit file, the whitest white is 1023 and the blackest black is zero.  This is reflected on the waveform.  If you output to "video levels", or 64-940, the transform from full range to video levels will be done upon rendering.  If you need video levels for your display, it is a selection in the preferences.

 

So one can view the waveform as normal. 

 

If you are grading in LOG and outputting LOG for a filmout, then things could be different as one would be grading viewing through a film emulation LUT, and the scopes would be showing a LOG image. If I remember correctly, film white was around 800 and blacks 125, but I really don't remember.  But, today, who grades solely for a film out?  I haven't made a grade for filmout since 2011.  My last filmout was done in 2013 and we graded for DCP and converted that version to LOG for a filmout with some adjustments made to the conversion to make a nice negative.

 

So Evan, nothing to see here.  Go back to work :)

I understand. I think. So if you were grading a 10 bit image, anything over 940 or under 64 will be blown out or crushed after it is saved as a rec709 image.

 

 

Would be nice if they gave you the option to change the scale to IREs. Most other monitors I've seen use that scale. Perhaps it's not useful for grading 10 bit images though. But it does go up to 120 and down to -40. Seems like that would give you some more latitude.

Thanks!


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#6 Bruce Greene

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Posted 05 November 2017 - 01:52 PM

I understand. I think. So if you were grading a 10 bit image, anything over 940 or under 64 will be blown out or crushed after it is saved as a rec709 image.

 

 

Would be nice if they gave you the option to change the scale to IREs. Most other monitors I've seen use that scale. Perhaps it's not useful for grading 10 bit images though. But it does go up to 120 and down to -40. Seems like that would give you some more latitude.

Thanks!

I think you misunderstand.  Nothing will be clipped between zero and 1023.  If you see it on the waveform, it's not clipped.


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Aerial Filmworks

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CineTape

Gamma Ray Digital Inc

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Broadcast Solutions Inc

Ritter Battery

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Tai Audio

Paralinx LLC

Technodolly

The Slider

Glidecam

Wooden Camera

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