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Color Spaces Problem

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Maciej Chmielewski
Color Spaces Problem
on Nov 24, 2018 at 11:12:56 pm

Hi everyone,
I’m using Avid Media Composer on MacBook Pro 2018. I’ve got some problem defining what setup should I use. I have HD footage, my Avid color space is YCbCr 709. My MacBook display is set to rec.709 gamma 2.4. My work is to be delivered to broadcast station. So far so good. But my external monitor which I’m using to color correct doesn’t have rec.709 color space. It is Benq BL3201PT 32’. I’ve got is set on sRGB - don’t know the gamma value for now (but I expect it to be 2.2).
So I am wondering, how is is all affect final product brightness, since the main difference between the rec.709 and sRGB is gamma value.
Is there any workflow that I should follow to minimize the difference in this color spaces, but mostly brightness? Also, I can’t afford to change my monitor.

Thanks


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Shane Ross
Re: Color Spaces Problem
on Nov 25, 2018 at 3:23:23 am

If you need to deliver a show to be broadcast over the air, then you'll need to have the proper setup to view that, and grade that, to meet online specifications. This means the computer needs to have an input/output device connected to it (Avid DNxIO, AJA Io4K, Decklink options) that are connected to a calibrated broadcast monitor that is capable of the Rec709 color space. You'll also need scopes capable of displaying a waveform monitor and vectorscope, so you can see that your colors are in the right range, and that your whites don't go above 100 IRE, and blacks below 0 IRE. You'll need to export a video master that meets certain video specifications, or it will be rejected by the network Quality Control.

Viewing this on your MacBook display won't be accurate. The SOURCE and RECORD monitors in the Avid interface aren't color accurate. And while Avid does have the scopes available in the COLOR workspace, because it doesn't monitor the video signal coming out of the computer...it's not in the signal path. So it won't see that your whites might be a tad hot.

I don't say this to be mean...just telling you that when it comes to broadcast delivery, the video needs to meet certain specs, and to monitor that, and truly see what your image looks like, you need certain equipment.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Maciej Chmielewski
Re: Color Spaces Problem
on Nov 25, 2018 at 9:24:55 am

Thank you Shane.
First of all, I don't find your answer to be mean, I find it informative and precise. I understand the limitations of my setup, but to be honest with you, I became more interested how it is all works in theory than how to meet the specs. More or less, I know how the viewing setup should looks like. But I also have some questions.
1. Let's assume for a moment that I have all the right equipment listed. Do I need an external waveform monitor and vectorscope or the calibrated broadcast monitor built-in scopes will do the trick?
2. I'm also curious about this gamma differences. I forget to mention that I use Davinci Resolve to CC my footage. In this scenario I import rec.709 2.4 gamma video to Davinci. Since my external monitor only uses sRGB color space I set the project settings to rec.709 2.2 gamma. After CC I export but using rec.709 2.4 gamma profile. Please tell my how much will it affect final brightness of the image comparing to the source footage.


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Shane Ross
Re: Color Spaces Problem
on Nov 26, 2018 at 6:37:23 pm

[Maciej Chmielewski] "1. Let's assume for a moment that I have all the right equipment listed. Do I need an external waveform monitor and vectorscope or the calibrated broadcast monitor built-in scopes will do the trick?"

I have one built into my monitor, Flanders Scientific model. If I DIDN'T have those, I'd use ScopeBox on a MacMini. Hardware scopes are NOT cheap.

[Maciej Chmielewski] "2. I'm also curious about this gamma differences. I forget to mention that I use Davinci Resolve to CC my footage. In this scenario I import rec.709 2.4 gamma video to Davinci. Since my external monitor only uses sRGB color space I set the project settings to rec.709 2.2 gamma. After CC I export but using rec.709 2.4 gamma profile. Please tell my how much will it affect final brightness of the image comparing to the source footage."

It'll be slightly darker than what you graded to. Computer Monitors tend to be brighter than TVs, and yes, 2.4 opposed to 2.2, slightly brighter, in the mid range.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Maciej Chmielewski
Re: Color Spaces Problem
on Nov 28, 2018 at 12:54:24 pm

Ok, I get it now. So I’m going to use Scopebox with macmini. What i/o device do I need to get refference from davinci running on macbook? I assume that for macmini I could use any extetnal monitor?


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Shane Ross
Re: Color Spaces Problem
on Nov 28, 2018 at 7:05:44 pm

OK, from Davinci, you need to use a Blackmagic Design Product. And the ULTRASTUDIO line is the ones with THUNDERBOLT connectivity. The Ultrastudio MINI MONITOR is the cheapest, simplest way out. Thunderbolt connects to your computer, and then HDMI and SDI outputs. NOW...that MacMini will also need a device to bring in the video...so get an Ultrastudio MINI RECORDER that also has SDI and HDMI on it...and just put a small cable between them.

Both of those devices are about $145 US.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Maciej Chmielewski
Re: Color Spaces Problem
on Nov 28, 2018 at 9:39:42 pm

That’s it! Thanks for your help.


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Maciej Chmielewski
Re: Color Spaces Problem
on Nov 29, 2018 at 10:17:18 am

One more question. Why can’t I connect macbook with mac mini just with thunderbolt without any i/o device?


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