Understanding rec709, and grading for that delivery.

[Thomas Koba]

I've never gotten my head around it. But I just got a job, where the client need to deliver DPX's for a DCP master. They "want it to be graded to rec709 standards". Does this mean what I think it means:

I´m grading without a HDTV monitor. Just using my two EIZO computer monitors.

1. When we import RED footage into Davinci, we have more headroom than the 709 standard allows.
2. When exporting, we can choose to compress this higher dynamic range into the rec709 space, which is not as big.
3. I use the full range of my scopes when grading, not taking into considerations the 0-16 and 235-255 limits of rec709. This will automaticy be taken care of on export, when I choose 709 standard.
4. Should I use a 709 LUT when grading?

Is this how it should be understood, or is it much more complicated?

 

[MichaelP]

I would start with a calibrated Rec.709 monitor. From there external scopes. Also, the room environment needs to be considered so as to not influence or contaminate the monitor itself (such as a strong overhead light, or completely dark). It is not an automatic create Rec 709 on export from a full range correction. Although you will get something, it most likely will not be what you expected.

Michael

 

[Luis Otero]

Cannot understand why they want to limit the color space to Rec.709 if it will be used for DCP generation. Big restrictions, IMHO, that will hurt the colors projected (not real blacks, and crippled whites).

 

[Marc Wielage]

I believe the client is misinformed. We traditionally use XYZ color space for a digital theatrical master (DCP), not Rec709. Rec709 would be used for home video and broadcast HD. Generally, two different paths and two different LUTs are used for each standard. You can't automatically get two masters out of one transfer.

I think what's more often done is to color-time the entire feature in XYZ color space for digital theatrical, using a projector. Once this is approved, a DCP is made from those files. Later on, a separate Rec709 version is done (either using a calibrated HD monitor or the projector switched over to Rec709 color space). I suspect they're trying to do it backwards.

Get the distributor's delivery specs and see what you have to wind up with, and come up with a workflow that will meet the schedules you need to reach.

 

[Tom.Wong]

does any kind of transform lut exist to convert the xyz project to 709 standards? or do you basically have to do the xyz version and color match by eye and values in a separate 709 version every time?

 

[Luis Otero]

Tom,

Yes, what is done, if it is wanted to do it correctly, is to color correct to the most "strict" color space, then use transformation LUTs that will adjust the grading to the other color spaces specifications (sRGB, Rec.709, etc), hence avoiding the need of performing multiple gradings.

 

[Tom.Wong]

strict meaning not doing anything too wild and wacky and pushing levels to clip on the top and bottom? i've always been hunting for the proper answer for all this. i live in a very 709 world in tv and broadcast. xyz grading is a whole different animal and i really want to learn more about it. do you have resources for these transform luts? please PM me if you can.

 

[Luis Otero]

Will do it tomorrow. I am 3 hours ahead (and tired) of you ;-)

 

[Luis Otero]

Tom,

Just sent you a PM...