Prores to DCP, slightly les bright.

[Fremax]

Hi!
I am converting A Prores4444 REC 709 exported from Premiere Pro.
After several tryouts, the best settings for colour conversion are:
REC 709 but with input gamma 2.4 (this is actually the same setting as REC 1886)
RANGE MPEG 16-235

When I compare the DCP .mxf video file with the original prores file in Premiere, it is almost perfect.
The only thing is that the highlights/maximum brightness is somewhat lower. I can see this on the scope as well.
Is there a way by adjusting Input power/Threshold A B, to adapt this? Standard 'simple gamma linearised for small values' did not give a good result.

Or could the white point adjustment do that? (but I guess that's more for colour temperature)

Any help appreciated

[Carsten]

As a matter oft fact - everyone is today still referring to rec.709 - however, that is a deprecated standard from the early nineties, and it never mentioned an actual display gamma value (because it implied the natural gamma of CRT monitors of the time). Whenever equipment nowadays claims rec.709 compatibility, it actually means it is using BT1886. So, all modern digital HD equipment can be assumed to be BT1886 compliant and is targeted towards a display gamma of 2.4


As to the highlights - it is very complicated to get this straight, there e.g. is a reoccurring issue known as 'Quicktime gamma shift' which can take you a day of reading and afterwards you still don't know how to deal with it properly. This is not a specific DCP-o-matic weakness, but one between codecs, operating system, editing software, monitoring systems, different colour spaces, etc. In the end - you need to go to a properly calibrated cinema and see wether you like what you see.

[Fremax]

Thank you for your reply.
You are confirming exactly what I found out by trial and error.
Good to know I was right!

[Carsten]

Another way of looking at gamma 2.2 vs. 2.4 is the viewing environment - 2.2 is generally considered as the basis for living-room, computer display, news watching, etc., with higher display gammas tailored towards darkened home cinema, and then at 2.6 in the 'real' cinema at DCI specs.

So, if you're concerned about blacks and highlights, you're more after 2.4 than 2.2 (the conversion to DCI 2.6 is done within dcp-o-matic).

[Fremax]

I will check my converted DCP on a calibrated screen, as I have access to a professional Color Grading facility!
But indeed the 2.4 gives great results
thanx again

[babyvolcano]

Hello! I am having a similar problem but changing the gamma to 2.4 made the DCP even darker. Are there any other settings in the Colour conversion window that I need to adjust other than input power?

I was able to preview the DCP using DaVinci Resolve which is how I noticed the brightness shift.

Any help very much appreciated.