I looked into this around the time I was looking into NCLC colourspace tagging for QuickTime.
The first thing that I found was that the gamma for sRGB and rec.709 isn’t consistent. It is simplified/ summarised as 2.2 or 2.4 but it is subtly different. Don’t ask me. Ask the colour scientists.
What I read - The overall gamma of sRGB is approximately 2.2. Whereas Rec. 709 uses BT1886 gamma curve approximately 2.4.
The other thing I did before the ColourSync option appeared in Flame, was to build a LUT that took my rec.709 media and removed the gamma and made a sRGB gamma version. I wanted to see if this would be a better way of presenting to clients.
This conversion made the media look washed out on my Flame but then I am working on rec.709 footage and my monitor is not shifting from rec709 to sRGB to compensate regardless of how I tag it.
The real test is how my quickTime looks on a mac. I export my client WiPs without using colorSync compatibility but now that we have it I can use three exports to compare on a mac using QuickTime.
The one on the left, (1-1-1) is not colourSync compatible and is the traditional way I send my wips to clients. I know it is wrong in terms of gamma but stay with me.
Middle is my newly created sRGB version. I have actually changed the look of my pixels not just tagged it differently and on export it has been tagged (1-13-1). It looked different on my Flame with my rec709 monitor not able to correct for the gamma shift.
The one on the right is my rec.709 WiP being given the correct colourSync treatment. (1-2-1) getting a gamma of 2.4 injected into the NCLC tagging.
When I view them in QuickTime I get this:
Top is my regular export with no colorSync. (1-1-1) rec.709 being displayed incorrectly using Apple’s interpretation of the rec.709 display gamma (1.95).
Middle is my conversion to sRGB (1-13-1)
These two are close but no cigar.
Bottom is my colorSync compatible export (1-2-1) with a gamma of 2.4 injected into the NCLC tagging.
It looks wildly different to both other versions. I would have expected it to resemble the sRGB version but it doesn’t.
Now is this a better representation of my rec709 version I see in my Flame suite? Maybe. It depends on how we look at it and in what environment. How bright my client has their monitor.
At this point my enthusiasm melted and I decided to keep doing it the way I have always done it and to keep answering the same questions I always get about it looking different on their monitors.