[Tig] QC a DCP
rogermamo at gmail.com
Sat Feb 18 20:07:35 GMT 2012
...and back to the LUT and RGB2XYZ threads. Most DCP softwares come with a
player to play out you .j2c , 12 bit, XYZ, 2.6 gamma (wow) material and to
check if anything went wrong right after packging (though many only support
8 bit play). But, for a proper QC in my opninon, this should be done in
the environment the DCP was supossed to play, A.K.A, a digital cinema
theatre, with a a calibrated DLP projector, and a (or two) trained human
eye present etc. Also, most DCP softwares do come with a basic Rec.709 to
DCI compliant XYZ color space conversion LUT. In the (not so) old days
when we (I) graded DPX for film out, I had to check my monitor in the
grading suite, run to the lab projection room, and to a certain degree say:
"... ok, we're almost there" . We kind of joked, because it was then we
"used" our LUT: a lab technician, in charge of the printer, to better
calibrate it so it matched with a fair good accuracy what I was seeing in
my monitor (giving lots of headroom to the video and film color space
changes). Never had the opportunity to do a " butterfly" check on a printed
material. wich is and was the best solution. But as far as your question
goes, I think that will be the differential that companies that offer DCP
services will have: a good Quality Check *person*, in my opinion, a trained
colorist, to validate not only the integretiy of the DCP, but the final
asthetical result, that was intendend in the master suite by him, the DOP
2012/2/18 Carl Skaff <carl at stopp.se>
> Sohonet http://www.sohonet.co.uk sponsors the TIG.
> Support from Nucoda www.imagesystems.tv
> Support from Blackmagic Design http://www.blackmagic-design.com/
> Hey all
> Here is topic for discussion.
> How do people QC a DCP?
> In the old days (not too long ago) we used to shoot out to Neg and then to
> a Print.
> Then the best way to QC the print was (if you ask me) to do a butterfly
> splitscreen between the digital projector (playing the graded DPX on your
> grade-system) and the analog film projector.
> That way we could check that the grade was ok and translated fine with our
> LUTs and we could determine if the added/removed grain/noise works fine
> with the filmgrain. Etc etc
> Now when we deliver DCP it should be possible to have a smart application
> that can play the graded DPX in splitscreen to the DCP.
> I suppose it should be fairly easy if you are on a DCI projector in P3, XYZ
> bla bla bla and all that.
> But if I was to grade on a Rec709 monitor/projector I suppose the app would
> need to be able to load the correct convertionLUTs on either side.
> That way we could QC the DCP, not only to check the convertion but also
> make sure that the compression didn't mess it up. And if we see an artifact
> we could just wipe over the original DPX to compare.
> Anyone know of such an app or am I thinking about this the wrong way?
> How do YOU qc your dcp?
> (Sent from mobile device)
> *Carl Skaff*
> Stopp Stockholm
> Office +46 8 50 70 35 00
> *Stockholm | Los Angeles | Linz*
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