Color DPXs

[ThomtheEditor]

Hey guys, we're having an issue with final effects and grading.
We are grading native R3d's in Color, some shots are going to combustion for vfx, the rest just straight back into fcp for hd & film outs as ProResHQ.

Our issue is this: getting effects back from the combustion artists there is a significant gamma shift, they say it's a combination of gamma shift on the output of color and a smoke layer that is going into the film. We did a quick frame comparison test with the AJA DPXtoQT translator utility and the before frames and the frame in color look almost identical, the one back from them very shifted; my question, is there anything that causes a gamma shift from color to dpx; or is it on their output on the way back?

We're kinda stuck not knowing the best way to proceed,
Thanks,
~T

 

[jake blackstone]

Hey guys, we're having an issue with final effects and grading.
We are grading native R3d's in Color, some shots are going to combustion for vfx, the rest just straight back into fcp for hd & film outs as ProResHQ.

Our issue is this: getting effects back from the combustion artists there is a significant gamma shift, they say it's a combination of gamma shift on the output of color and a smoke layer that is going into the film. We did a quick frame comparison test with the AJA DPXtoQT translator utility and the before frames and the frame in color look almost identical, the one back from them very shifted; my question, is there anything that causes a gamma shift from color to dpx; or is it on their output on the way back?

We're kinda stuck not knowing the best way to proceed,
Thanks,
~T

film outs as ProResHQ out of FCP? Are you grading in LOG for the filmouts or you grading in REC-709 with Lin to Log conversion at the very end? Do you have all the LUTs that you'll need for the filmlout and gamma conversion? Not sure why you want to do it all the hard way. So, here is an easy way- conform r3d files in from an EDL with Monkey Extract or Crimson, export Log DPX for grading and effects work. Or do all grading with conformed timeline in Color in Log and export FX shots as LOG DPX. No more gamma shifts, much better quality. Problem solved. Contact me, if you still have questions...

 

[M Most]

Hey guys, we're having an issue with final effects and grading.
We are grading native R3d's in Color, some shots are going to combustion for vfx, the rest just straight back into fcp for hd & film outs as ProResHQ.

Our issue is this: getting effects back from the combustion artists there is a significant gamma shift, they say it's a combination of gamma shift on the output of color and a smoke layer that is going into the film. We did a quick frame comparison test with the AJA DPXtoQT translator utility and the before frames and the frame in color look almost identical, the one back from them very shifted; my question, is there anything that causes a gamma shift from color to dpx; or is it on their output on the way back?

What is the monitoring path - both yours and theirs?

 

[ThomtheEditor]

I've been told today that we aren't doing a filmout now, but rather just 1080 SR tape, oh well, anyway, am i missing something that when i select dpx output i don't get any options for lin or log, it just sets itself to linear with no dropdown options?

 

[Antoine Fabi]

Hi Jake,

I am not sure i understand correctly, my english is not that good.

I use Clipfinder that i like very much.

Do you suggest to convert R3D directly to 10 bit log AFTER doing first light grade, or do you suggest to leave the R3D ungraded at all (exept for correct color temp) and export to DPX log and then grade in Color, and finally export DPX Log as final ?

or are you suggesting to do light grade in Rec709 gamma, and change it afterward to log just for exporting to Color ?

Thanks

Antoine

 

[jake blackstone]

Hi Jake,

I am not sure i understand correctly, my english is not that good.

I use Clipfinder that i like very much.

Do you suggest to convert R3D directly to 10 bit log AFTER doing first light grade, or do you suggest to leave the R3D ungraded at all (exept for correct color temp) and export to DPX log and then grade in Color, and finally export DPX Log as final ?

or are you suggesting to do light grade in Rec709 gamma, and change it afterward to log just for exporting to Color ?

Thanks

Antoine

Oh, not at all. I'm not suggesting doing grading in Rec-709 color space for the filmout. For that you will need to end up with Log DPX files. You have to either map the r3d to Log DPX with RedLog gamma in something like RC or RR or Clipfinder(?) or by grading in Scratch in RAW Log. I'm not familiar with Color, but I think you can grade in Log as well from r3d? But it doesn't matter anymore, as all they are doing now is just video, which generally means Rec-709.

 

[jake blackstone]

I've been told today that we aren't doing a filmout now, but rather just 1080 SR tape, oh well, anyway, am i missing something that when i select dpx output i don't get any options for lin or log, it just sets itself to linear with no dropdown options?

I could be wrong, as I'm not experienced with Color, but I would imagine, that you'd need to select RedLog gamma for the Log DPX? May be someone familiar with Color can correct me. But if you're doing just video, then you don't need work with Log DPX anymore. BTW, is your deliverable will be recorded on HDCam SR? For just deliverables you can use regular HDCam, no 4:4:4 needed, unless I'm missing something?

 

[Antoine Fabi]

Hi Jake,

So if i understand correctly, the best way is to first choose Log gamma space in Clipfinder, then grade (first light grade) on a calibrated computer monitor and export as 10 bit Log DPXs.

But then, since the computer monitor is apprx Rec709 gamma 2.2, do i need special LUTs for the monitor ?

Antoine

 

[jake blackstone]

Hi Jake,

So if i understand correctly, the best way is to first choose Log gamma space in Clipfinder, then grade (first light grade) on a calibrated computer monitor and export as 10 bit Log DPXs.

But then, since the computer monitor is apprx Rec709 gamma 2.2, do i need special LUTs for the monitor ?

Antoine

Yes, you're correct on first point. On the monitor choice, I just wouldn't recommend LCD monitor for grading, but if you do, it needs to be set to something like P3 profile (I believe DreamColor has DCI setting):
chromaticity:
white: xy[0.3140, 0.3510]
red: xy[0.6800, 0.3200]
green xy[0.2650, 0.6900]
blue xy[0.1500, 0.0600]
gamma/response: 2.6
Luminance set at 54.82 cd/m2 (16 ft-L) not a 100 cd/m2 (29 ft-L) like video!!!
This is a monitor calibration and not a LUT. In order to create a viewing LUT you'd need something like CineSpace. Remember, if you decide to go this route, everyone working with these LOG DPXs has to set their monitors to the same specs, otherwise you're back to shifting gammas, levels, colors etc.

 

[Antoine Fabi]

Thanks a lot Jake!

Antoine