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Adobe Premiere cc 2019 brand new color management technical details directly from Lars Borg, chief color engineer, Adobe PrPro

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Chris Wright
Adobe Premiere cc 2019 brand new color management technical details directly from Lars Borg, chief color engineer, Adobe PrPro
on Oct 23, 2018 at 2:08:59 am

I thought this would be useful for the cow, moo!

From Lars Borg, chief color engineer, Adobe PrPro

["CM" refers to the new Color Management option in the Edit/Preferences dialog.]



- CM off is great if your screen matches the media on the timeline. Works well for Rec. 709 and sRGB and YouTube delivery.



- CM on is useful when that's not the case, and you want your display to reproduce the color appearance of the timeline on a reference monitor.

As always, this assumes your display is reasonably calibrated or characterized.



Examples:

1. Timeline is 709, display is P3. Without CM, the display appearance would be too saturated and would not match your export.

2. Timeline is 2020, display is not 2020. Without CM, the display (709, sRGB, or P3) would look washed out and would not match your export.

3. Timeline is 709, display is sRGB. With CM off, the display will match what a YouTube viewer will see on her sRGB display, which will be slightly washed out (gamma ~0.9) compared to a 709 reference monitor. With CM on, the mid-tones on the sRGB display should match a 709 reference monitor, but some shadow details are lost, as 8bit sRGB encoding in the shadows don't have the fine granularity of the 8-bit 709 shadows; the 20 lowest 709 codes are crunched into the 7 lowest sRGB codes.

4. Timeline and display are both 709. No need for CM, it should make no difference, turn it off.

On loss of values [point 3 above]:

The 78 lowest 10-bit 709 code values are crushed into the 28 lowest 10-bit sRGB values

10-bit 709 codes 0 to 14 are mapped mathematically to 10bit sRGB code 0 (if rounded to nearest).



But most sRGB displays are only 8 bit, so:



The 19 lowest 8bit 709 code values are crushed into the 7 lowest 8bit sRGB values

8bit 709 codes 0 to 6 are mapped to 8bit sRGB 0 (if rounded to nearest).

Some video cards might use floor instead of round:

8bit 709 codes 0 to 8 are mapped to 8bit sRGB 0 (if floor is applied instead of round)



The 78 lowest 10-bit 709 code values are crushed into the 8 lowest 8bit sRGB values

10-bit 709 codes 0 to 26 are mapped to 8bit sRGB 0 (if rounded to nearest)

10-bit 709 codes 0 to 35 are mapped to 8bit sRGB 0 (if floor is applied instead of round)



Many displays are "sRGB-in-name-only", SINO. Even when calibrated to sRGB, a SINO display can be off target, as most calibration tools take very few samples. So a SINO display might show less details than what's represented in an sRGB encoding. (Remember 6-bit displays?) However, the detail loss would be there regardless of CM on or off.



Just for comparison:

When exporting 8-bit full range RGB to 8-bit narrow range YCC, around 83% (5/6) of the original code values are lost (even before chroma subsampling). The result is similar to losing the last bit in 8bit RGB. The losses are spread out evenly over the entire color volume, each mapped to nearest neighbor, so it's it's hard to notice in most cases. It can show up as banding, especially in dark gray skies.


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John Heiser
Re: Adobe Premiere cc 2019 brand new color management technical details directly from Lars Borg, chief color engineer, Adobe PrPro
on Oct 23, 2018 at 9:00:37 pm

This make my brain hurt.

John Heiser
Senior Editor
o2 ideas
Birmingham


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