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Neil Evely
SMAC 2011 - Luma/Chroma difference between source Quicktime Smoke output
on Jun 7, 2010 at 11:00:43 am

Hi all -

We have Smoke 2010 and Smoke 2011 running side by side here and have experienced some oddness with the 2011 vsn. We have captured material via an FCP on an AJA card, both at SD and HD. When importing the material (10 bit Quicktimes) into 2010 the picture is identical. The 2011 vsn seems to be changing the picture and making it lighter, by a tiny but noticeable degree. This is happening via soft and hard import.

Can't figure out why, you'd expect the 2010 to be the least reliable...

If i compare the source material in FCP by the Smoke UI you can tell the blacks are less crushed and the colours ever so slightly less saturated.

Has anyone come across this as yet? I can't believe its a bug or oversight? We are definitely working at the same format as the source material - which for SD is RGB at 10 bit Uncompressed.

Its not the display either as we have laid to tape and checked the picture back.

Any advice gratefully received.

Thanks
NEil

Neil Evely
London


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Brian Mulligan
Re: SMAC 2011 - Luma/Chroma difference between source Quicktime Smoke output
on Jun 7, 2010 at 1:32:31 pm

Are you using a 2yuv codec in FCP? People have reported a similar issue.

here is an except from another post on Smoke-News

had the same issue here & cost us a lot of nerves...

the reason seems to be working YUV in FCP - if the sequence is set to RGB everything is fine here!

seems like FCP/Apple/QT whoever wants to do some "intelligence" when dealing with yuv<>rgb, which is different from just gamma shift. i suspect some "headroom intelligence" too, but havent figured out values so far. - obviously i have only checked the way from FCP to smoke (& back), not sure, if the QT is coming from elsewhere ...




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Neil Evely
Re: SMAC 2011 - Luma/Chroma difference between source Quicktime Smoke output
on Jun 7, 2010 at 5:00:27 pm

Thanks Brian, yes, we're just using the YUV (v210) default - so you suggest importing the footage and making an RGB sequence from it before Smoke imports it?

At the mo, some of our media is pre existing TVC's so don't require any XML's etc, so we simply point the Smoke at the capture scratch and soft import the full file.

I've exported out QT's from Smoke too and pushed them back into FCP, some work, others don't. SD YUV with a 1.8 Gamma setting seems identical when i pull it back into FCP. HD needs to be 10bit YUV (v210) but still needs a minor colour correction in FCP to bring back the midtones, then its indistinguishable. Im testing this with PAL SD/HD bars & tone FYI.

Its strange, because if you export out an HD QT from Smoke then pull it back it, you'd expect to see the difference but Smoke see's it exactly the same as the source, but FCP needs a tweak.

Neil Evely
London


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Brian Mulligan
Re: SMAC 2011 - Luma/Chroma difference between source Quicktime Smoke output
on Jun 7, 2010 at 8:49:41 pm

Seems that if you edit in RGB in FCP then you will be fine.



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Morten Balling
Re: SMAC 2011 - Luma/Chroma difference between source Quicktime Smoke output
on Jun 10, 2010 at 2:29:27 am

It sounds like different gamma curves. What version FCP and OSX are you running? Snow Leopard changed Mac's gamma from 1.8 to 2.2.

What OS do you run Smoke on? Linux or OSX?

Best regards

Morten Balling


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Neil Evely
SMAC 2011 - Luma/Chroma difference between source Quicktime Smoke output - UPDATE
on Jun 30, 2010 at 10:16:32 am

Heres an update on this little problem:

We are running Smoke 2011 on Mac Pro - Snow Leopard.

Since my last post, we are happy with the SD Quicktimes from Smoke regarding colour and luma. We are now using the YUV codec and it looks like l the SD files match up to our system generated 100 UK Bars.

The problem with rendering at RGB is that if we are laying to tape from FCP, we have to render the file, which is essentially changing the format and of course it takes time.

Neither of the RGB or YUV files work for HD export, either the yellow/greens are darker or the reds/blues are darker depending on the codec - basically none of them are accurate.

Importing any HD quicktime from Smoke, back into Smoke, seems OK. Its like Smoke knows the problem and caters for it, but play it anywhere else and its wrong.

I've considered altering the gamma or applying a LUT to make the file accurate on export, but that would mean any re-import back in Smoke (which is likely) would then be wrong (because Smoke would compensate)....

Am i making sense?

Has anyone experienced similar issues?

Thanks
NEil

Neil Evely
London


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Kevin Adams
Re: SMAC 2011 - Luma/Chroma difference between source Quicktime Smoke output - UPDATE
on Aug 23, 2010 at 8:26:12 pm

Hi Neil, I'm having the exact same issues, makes a "tapeless" workflow extra fun...

Kevin Adams
Seattle


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Neil Evely
Re: SMAC 2011 - Luma/Chroma difference between source Quicktime Smoke output - UPDATE
on Sep 27, 2010 at 4:42:56 pm

Hi Kevin, not sure if you've had any more luck with this, but we found that by using RGB for HD export and adjusting the Gamma on output to 0.818 within the Smoke settings, it gave an accurate export file that when compared to a graded DPX, looked exactly the same. It was good in FCP and on re-import as well.

I think you can add this into the Smoke set-up too.

Let me know if this works for you!

NEil

Neil Evely
London


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