TIFF XYZ export problem

Hello !

I want to create DCDMs in order to package DCPs for theatres.

Therefore, when I receive my DSM, I put it in DaVinci Resolve so I can export a TIFF XYZ 16 bits sequence that I put into easyDCP Creator to compile the DCP.

I achieved few tests and it appears that when I use the "TIFF XYZ 16 bits" preset in Davinci and compare my DCP with the DSM, the DCP is a bit darker.
However, when I use the "TIFF RGB 16 bits" preset, use that sequence to package the DCP and then compare the DCP and the DSM, the colors match.

As I really want to follow the DCI recommandations, I do want to have the TIFF sequence before I create the DCP because actually, I transcode my DSM directly into Jpeg 2000 XZY color space and use that sequence to create the DCP, which is not DCI compliant.

Thanks in advance for your help


FYI

I did my tests on a QuickTime ProRess 422 HQ (gamma 2.4).
DaVinci Resolve 12.5.2.010.
iMac (Retina 5K, 27 pouces, fin 2014)
4 GHz Intel Core i7
16 Go 1600 MHz DDR3
AMD Radeon R9 M290X 2048 Mo

one way to do it, is to explicitly do it with a resolve OFX.

situation A) = you have a lut in your settings (a master LUT )
1) go in your timeline color and add TWO nodes at the back end: put your master LUT in the second to last
situation B) = you DON'T have a lut in your settings (a master LUT )
1) go in your timeline color and add ONE nodes at the back end

2) in the last node add the resolve OFX [color space transformation]
3) set:

rec709
gamma 2.4
CIE XYZ <- (verify exactly the mane, I go from memory)
gamma 2.6

export TIFF 16 bits full range...

to QC that, relink the export, place the same node at the end and do the opposite:

CIE XYZ <- (verify exactly the mane, I go from memory)
gamma 2.6
rec709
gamma 2.4

they should look correct.

If you have a contrast/gamma differential, it could be a scaling issue.

BTW, welcome to the forum!

Hi Walter, and thanks for your answer !

As I receive graded files, I put myself in the situation B.
Indeed, after I put the OFX on the node and set it as you said, the color transform looks good. However, when I compare with the source, it appears that there is a gamma shift. My export is a bit darker than my source, but the difference is very (very !) small. That is why I would like to ask you what you meant when you said

"If you have a contrast/gamma differential, it could be a scaling issue."

Moreover, there is still something that I can't seem to understand.

When I export, I can chose between "RGB" (8 or 16 bits / LZW compression or no) codec OR "XYZ" (16 bits / LZW compression or no) codec. I can't seem to find your "TIFF 16 bits full range". Is it in the "advanced setting -> Data Level -> Full" ? If it is so, I still have to specify "RGB" or "XYZ" codec.
If I chose "XYZ" codec, my export looks like a double transform has been applied (there is too much green).

When using "RGB" codec it is the export with the small gama shift. But in that case, I feel like I am cheating because I am in the RGB codec instead of XYZ.

In a second test, I just imported my ProRess 422 HQ file, and in "Color", I added a 3D LUT (DCI -> Rec709 to DCI XYZ) (I don't apply the LUT on a second node) and export as "TIFF RGB 16 Bits".
When I compare the DCP I do from that sequence, everything matches perfectly. The only thing that is disturbing me is that I am in a RGB codec instead of XYZ.

I feel I miss something !

Thanks again for your time and your warm welcome

Hey Walter,

I just tried your recommendation on using the color transformation OFX to transform from Rec709 gamma 2.4 to CIE XYZ and it worked brilliantly. When I brought in my 16bit RGB TIFF sequence and applied the color transformation in the opposite order, the color matched the DCP spot on. Thank you!!

Just out of curiosity, what is the difference between DCI X'Y'Z and CIE XYZ? In the color management setting in resolve, in the drop down menu for timeline color space, I see both of those options and am curious as to what the difference is.

And by the way, I believe you and I are work neighbors. I work at Level3 next door. Small world haha.