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leon grin
rec709 calibrating problems
on Aug 29, 2013 at 9:40:55 pm

I'm new in all of this and have some very basic questions to ask. I have u2413 dell connected to gtx560 nvidia and trying to calibrate the display to rec709 for color grading with spyder4. I'm using dispcalgui and basiccolor display 5 as calibration software and getting identical results. As I know rec709 gamma is 2.2 (with overall gamma of 1.9 which I dont know what it means) but when playing a graded footage on srgb gamma 2.2 monitor (calibrated for srgb gamma 2.2) all shades of dark are missing and everything looks much darker. As I know srgb and rec709 should be similar (gamma 2.2?) but it seems that they are not. Maybe rec709 has lower gamma in darker areas? What I'm missing? What I made wrong?

Thanks,
Leon


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Joakim Ziegler
Re: rec709 calibrating problems
on Aug 29, 2013 at 10:48:58 pm

While there may be several problems here, you're getting a few things confused. Rec.709's "overall gamma of 1.9" is in the encoding curve. A problem with rec.709 has been that the spec only includes the encoding curve (what the camera uses to translate linear light into the spec's color space). This curve is not relevant for monitors. You'll want to calibrate your monitor somewhere between Gamma 2.2 and 2.4 to display video correctly. When you say "sRGB Gamma 2.2", I assume you're referring to sRGB primaries and a Gamma 2.2 curve, which is correct, since sRGB and rec.709 primaries are identical (but sRGB has a different curve).

Try calibrating to a pure Gamma 2.2 or 2.4 curve, and see what happens.

--
Joakim Ziegler - Postproduction Supervisor


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leon grin
Re: rec709 calibrating problems
on Aug 30, 2013 at 9:31:49 pm

Thanks Joakim,
If I'm calibrating to gamma 2.2 or gamma 2.4 I'm getting very different results that if it's calibrated to rec709 on dipcalGUI or basic color display 5. I guess that I'm doing something wrong with calibration maybe? In both programs there is no way to change gamma with rec709 option. Or...Bill is right, despite it's wide gammut 10bit 100% srgb display it may be that is just not good enough.

Thank you all
Leon


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Joakim Ziegler
Re: rec709 calibrating problems
on Aug 30, 2013 at 11:13:41 pm

Again, if your calibration software is offering "gamma 2.2" and "gamma 2.4" as an alternative to "rec.709", then they're referring to the gamma curve, and you should use 2.2 or 2.4. Many calibration systems sadly don't understand that the rec.709 curve is not suitable for anything but encoding and should not be given even as an option for monitor calibration.

--
Joakim Ziegler - Postproduction Supervisor


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Bill Ravens
Re: rec709 calibrating problems
on Aug 30, 2013 at 8:16:17 pm

Sadly, and I don't mean to be discouraging, but....
There is not a commercial monitor on the market that will ever display REC709 accurately. I know that's a pretty big statement, but, the fact is that the best you can hope for is to get the luma properties close at a single display intensity and the white point calibrated. usually, these calibrations occur at 100% IRE. The RGB color map for a monitor doesn't even come close to REC709. And there's not adjustment provided to correct it. The exception to this statement is a professional cc monitor, like an FSI, or similar. Otherwise, you'll pound your head against the wall to get the colors and luma values right at 100% IRE, only to have them go to hell at other luminances.



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Margus Voll
Re: rec709 calibrating problems
on Sep 7, 2013 at 5:03:56 am

I'm playing with Eizo Color series monitor now with Light Space CMS.
Exiting about it is that resolve V10 can be managed by Light Space so you can calibrate
the full video path and know exactly if you nailed it or not. I'm running v10 beta now
and tested the feature yesterday.

If it works out it may be the poor mans solution for monitoring.

I agree on that common desktop monitors do not cut it usually specially after you have been
behind Penta or Fsi etc.

--

Margus

http://iconstudios.eu
https://vimeo.com/iconstudioseu/videos

DaVinci 9, OSX 10.7.4
MacPro 5.1 2x2,93 24GB
GTX 470 / Quadro 4000
Multibridge 2 Pro


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Bill Ravens
Re: rec709 calibrating problems
on Sep 7, 2013 at 5:27:44 pm

wow! you got MY attention....



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Margus Voll
Re: rec709 calibrating problems
on Sep 7, 2013 at 6:10:25 pm

Did some testing and it seems that 96 to 97 % accuracy with rec 709 is doable at least with my unit.

I have Eizo connected to the Deck Link 4K via hdmi.

Will test some more.

--

Margus

http://iconstudios.eu
https://vimeo.com/iconstudioseu/videos

DaVinci 9, OSX 10.7.4
MacPro 5.1 2x2,93 24GB
GTX 470 / Quadro 4000
Multibridge 2 Pro


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Bill Ravens
Re: rec709 calibrating problems
on Sep 8, 2013 at 9:48:52 am

So, are you using a LUT box?



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Margus Voll
Re: rec709 calibrating problems
on Sep 8, 2013 at 7:02:38 pm

no separate lut box as this monitor has internal lut ability.

You just upload lut to monitor and voila.

--

Margus

http://iconstudios.eu
https://vimeo.com/iconstudioseu/videos

DaVinci 9, OSX 10.7.4
MacPro 5.1 2x2,93 24GB
GTX 470 / Quadro 4000
Multibridge 2 Pro


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