Grading adjustment in Resolve for DCP creation

[Jack Jones]

I don’t know much about the Resolve specifics, but the following should be helpful;

You should make your DCP from your DCDM.

– The DCDM should be made up of full range 16-bit TIFF files, ideally broken down into reels.
i.e. filmtitle_r1_10000001.tif
– It should have a gamma conversion to match DCI spec of 2.6.
– It should be mapped into the XYZ colorspace using either a LUT or a Gamma Matrix.

Practical guidelines are available here: https://www.knuterikevensen.com/?p=312 and a full list of software/hardware are available on the DCP Wikipedia page.

Jack Jones
Freelance Nucoda/Baselight/DaVinci Colourist
—
https://www.jackjonescolourist.com

[Jean-christophe Savelli]

Thanks for the link Jack.

So for Davinci user, do you think a need to check all my grading with unscalled full range activated or not ?

[Chris Martin]

JC,

Are you making the actual DCP yourself or is another facility? If another facility is doing it then you should talk to them as it may be as simple as delivering them grading media and identifying that the working viewing environment was 709. The facility probably already has a process to transform the 709 to a DCP color environment (xyz, gamma 2.6).

If you are making the the DCDM yourself, which means creating a specific deliverable that is prepped for making a DCP, then as someone else has pointed out then you’ll need to use a LUT that properly transforms the project from one graded in a rec709 to one that accounts for the xyz color space of DCP. This transform LUT when properly used will compensate for both the xyz color as well as the change from 2.2 to 2.6 gamma environment. The great thing is this is all math and you don’t need to do any regrading to account for anything assuming you’ve been grading in a well calibrated rec709 environment and you are using a proper rec709toXYZ LUT. I know Resolve comes with a standard RGB to XYZ LUT but have not tried this one out.

Also if you’re doing a DCDM, make sure you are also delivering media that fits proper DCDM specs. We do 16bit tifs, converted to xyz color, and usually resolution will be 1998×1080 – 1.85 ratio (unless anamorphic). This means if you are working 1920×1080 you have a decision to make to either protect aspect ratio and box the 1920×080 in 1998×1080 canvas or crop top and bottom.

Still, if a facility is doing the DCP then there’s a good chance they could do all the above.

Cheers, Chris

[Jean-christophe Savelli]

thx chris i do it by myself because i don’t have the money to let a company doing this for me.

Waht i plan to do after reading all your advices :

– don’t touch my grade, keep it in rec709 and in legal video
– upscale to 2k (2048×858, 2.39 ratio)
– export from resolve in dpx sequence still in rec709

i will use opendcp to create the dcp package. I see in opendcp that we can feed with rec709 dpx sequence.

Is it something bad with this workflow ?

[Jack Jones]

With OpenDCP you have to feed it full range files otherwise your blacks will be lifted.

Full range, Rec. 709 16bit TIFF images with your chosen scaling for full, scope or flat. Do the Rec. 709 to XYZ transform in OpenDCP (which will account for the 2.6 gamma). Obviously ensure Logarithmic is unchecked.

Remember that with OpenDCP you have to compile the audio separately. You also need to know what servers it’ll be playing on as to whether or not you can create SMPTE packages or if you can only create INTEROP 24/48fps.

Do a 10 second test and check it in the EasyDCP player demo. Grab a still from it and do an XYZ to Rec. 709 transform to check it’s correct – the licensed software will do this transform but that’s a semi-work around.

Most importantly be sure to speak with whoever is screening it and find out the exact details of what you can provide.

Jack Jones
Freelance Nucoda/Baselight/DaVinci Colourist
—
https://www.jackjonescolourist.com

[Juan Salvo]

I’ve used openDCP in the past and have had major compatibility problems.

Someone looking to roll their own dcp obviously won’t be grading in DCi space. I hope they have a properly calibrated 709 monitor, otherwise everything else is pointless.

For colorspace transforms I’d actually recommend AE, particularly if you’re going the freebie route. There are a lot of great tutorials on this. But basically you grade 709 limited or full your choice, just know which. Then export out a qt. bring it into ae and using the interpret menu, define its colorspace, either 709 limited or full. Create a new comp with it, set your comp colorspace to DCi xyz then render out to an image sequence, and proceed with the dcp.

There are some not terribly expensive commercial software packages, that make much more standard and reliable dcps and will also do the colorspace conversion for you. I would strongly recommend one of these.

online editor | colorist | VFX | BD author

https://JuanSalvo.com

[Knut Jansohn]

[Jean-Christophe savelli] “The gamma between 709 and DCI is not the same (2.2 vs 2.6)”

That’s not correct. See http://forums.creativecow.net/readpost/277/8229

If you did the grading in a dark enviorement with gamma 2.2, then your midtones will appear to dark with gamma 2.6 in a dark ambiance (cinema).

Regards
K.

[Jean-christophe Savelli]

Ok i will do some test with AE for the export : both with full range and limited range to compare.

And yes you right Juan, the image will be darker, it is because i’m quite worry about that gamma question a the best solution to have a final dcp close to my graded 709 version, even the 709 gamma is 2.2, 2.4 or 2.5 it will be darker in DCP and i need to find the best solution to manage this.

[Knut Jansohn]

You could solve the gamma-issue with a 1d-lut. How to is well described in the resolve manual.

[Terrence Meiczinger]

Juan,

I’d be interested in hearing about your compatibility issues you have experienced with OpenDCP. It’s been tested successfully against all the major vendors. If it was sometime ago, you were probably caught up in the MXF Interop and SMPTE switchover. SMPTE is the default for OpenDCP, but there were a lot of broken SMPTE implementations in field which may have caused problems. If you still have any information, I would appreciate it, so if there are problems with OpenDCP I can work to fix them. Thanks.

-Terrence