LUT & Workflow (bmd-log, linear, rec709, dcp-p3...)

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Adriano Castaldini

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LUT & Workflow (bmd-log, linear, rec709, dcp-p3...)

PostThu May 09, 2013 4:20 am

After reading about LUT, log vs linear, rec709 and dcp-p3... I'm so confused!
So, guys, I would be grateful if anyone could clarify to me the workflow.

Let's assume that my workflow is based on BMCC + iMac + "old" Cinema HD Display as grading monitor, and the goal is to produce a color-graded movie in two versions: video-profiled and cinema-profiled.

1. I image that the BMCC has to be set on "film" profile, that is pretty flat. Is that log?

2. Now I import the footage into Davinci. Do I have to calibrate my monitor before that? If so, in this step do I have to set simply a "good" calibration (following the Calibrator Assistant of OSX) or I have to import/set a precise profile right now with ColorSync? And if so, which one? Rec709, dcp-p3, something "log-to-linear"? (I don't want to cut immediately the high dynamic range of the 12-bit RAW footage into a limited video-profile like rec709, I want to maintain the gamut/dynamic surplus to play with it grading or to recover under/over-exposed footage.)

3. I can image that once I've imported the footage into Davinci, I have to set a profile in Davinci internally. But which profile at this point? Directly rec709 or dcp-p3, or do I have to convert log-to-linear in order to do the grading job? And if so, when do I have to re-convert into rec709/dcp-p3?

P.S. Could you explain what is camera's zebra function, and how does it work?

Many thanks guys!
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rick.lang

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Re: LUT & Workflow (bmd-log, linear, rec709, dcp-p3...)

PostThu May 09, 2013 5:15 am

adrjork wrote:After reading about LUT, log vs linear, rec709 and dcp-p3... I'm so confused!
So, guys, I would be grateful if anyone could clarify to me the workflow.

Let's assume that my workflow is based on BMCC + iMac + "old" Cinema HD Display as grading monitor, and the goal is to produce a color-graded movie in two versions: video-profiled and cinema-profiled.

1. I image that the BMCC has to be set on "film" profile, that is pretty flat. Is that log?

2. Now I import the footage into Davinci. Do I have to calibrate my monitor before that? If so, in this step do I have to set simply a "good" calibration (following the Calibrator Assistant of OSX) or I have to import/set a precise profile right now with ColorSync? And if so, which one? Rec709, dcp-p3, something "log-to-linear"? (I don't want to cut immediately the high dynamic range of the 12-bit RAW footage into a limited video-profile like rec709, I want to maintain the gamut/dynamic surplus to play with it grading or to recover under/over-exposed footage.)

3. I can image that once I've imported the footage into Davinci, I have to set a profile in Davinci internally. But which profile at this point? Directly rec709 or dcp-p3, or do I have to convert log-to-linear in order to do the grading job? And if so, when do I have to re-convert into rec709/dcp-p3?

P.S. Could you explain what is camera's zebra function, and how does it work?

Many thanks guys!


Oh my gosh, do you also need a recipe for tea biscuits? I can give you that too if you need it.

Firstly your assumptions are not going to work. I have a late 2009 iMac and a 10 year old 23" Apple Cinema Display HD and I like the ACD's look (warm) better than the iMac (cool) but neither one will get you close to a monitor suitable for grading no matter how you try in my opinion... I've tried and realized that you need something recent from Flanders Scientific like the beautiful and capable CM171 DCI-P3 monitor. Sure it costs more than the BMCC, but it meets your requirements for both broadcast Rec.709 and theatre projection DCI-P3. You'll get lots of advice to try a Dreamcolor or a plasma screen. You are welcome to go that route if you want to but if you are serious eventually you will grade with the Flanders or its equivalent. Yes, the CM171 exceeds the broadcast screens that will view your video today, but tomorrow is another story so your are future proofing for a decade. And if you plan for digital projection, the latest Christie projectors will thank you for handing them DCI compliant data as you stated you wanted to do. Do you want to continue?

1) When you shoot in any BMD camera, if you shoot raw then you are automatically getting log or 'Film' curves. When you shoot in ProRes, you sound like you should always select 'Film' mode even if your deliverables may be in Rec.709 'Video' mode. The Flanders monitor will let you see what Rec.709 will look like with a press of a button or menu selection. The 12bit log data is expanded to 16 bits linear data in Resolve. John Brawley (aka one of the god-like cinematographers who selflessly share their knowledge on these forums) has told us the BMCC and BMPCC sensors capture more than 16 bits of linear data but the camera at this time records 12bit log internally. May the gods correct all my gross errors here.

2) See my earlier comments. There are lots of threads and online tutorials using Resolve. It is fairly straightforward once you have the recipe the tutorials provide so look around to see how you import your footage and define your projects to maximize your ability to grade the film. You have the right idea in that you can choose to keep as much data as you want during the import and grading process, especially if you will require special effects and keying for compositing. Resolve will let you continue to work in CinemaDNG but when you edit your video, you are likely going to export ProRes proxies and XML to FCP X for example. When your NLE work is done and you want to grade, you export an XML for Resolve to pick up your edits and apply it to your CinemaDNG clips.

3) When you want to produce your final deliverables, you make one or more selections from within Resolve to render your output such as a 2K version for cinema projection in 24fps using DCI-P3 and a HD version for broadcast in 23.976fps using Rec.709 colour space. That's the simple overview just so you feel comfortable with the process but you need to download the free Resolve Lite and start reading the manual. When you get your BMCC or BMPCC, you will get the dongle to enable the few extra features like noise reduction and deliverables in resolutions higher than 1080 HD.

PS Zebras can be enabled on the camera menu or attached monitor to show you where your image data is clipping, i.e. is exceeding the ability of the camera to record it accurately. It is okay if you are pointing the camera at the sun to see clipping there, or if you have specular highlights such as you might see on water or curved metal, but usually you don't want to see zebras for most other things like the sky or the side of a building so you must reduce your exposure until the zebras just barely go away. This is true if you are shooting raw. John Brawley has indicated you want to reduce your exposure a little further if shooting ProRes to protect the highlights. As you probably know, the term for this technique is called ETTR, expose to the right. That means shift the exposure so your data in a histogram appears almost at the right boundary. A very easy way to automate this if you are using an active sensor like the BMPC4K or BMCC EF or the BMPCC MFT is to press the Iris button. It will adjust the iris of compatible lenses to prevent clipping for log 'Film' recording or I believe to take an average scene exposure if shooting ProRes Rec.709 'Video'.

Hope that helps getting you going...

Rick Lang
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Adriano Castaldini

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Re: LUT & Workflow (bmd-log, linear, rec709, dcp-p3...)

PostThu May 09, 2013 2:33 pm

Mr. Lang! You are so generous and helpful! Many many thanks!

I've read carefully your reply. Just a doubt:
rick.lang wrote:3) When you want to produce your final deliverables, you make one or more selections from within Resolve to render your output such as a 2K version for cinema projection in 24fps using DCI-P3 and a HD version for broadcast in 23.976fps using Rec.709 colour space. That's the simple overview just so you feel comfortable with the process but you need to download the free Resolve Lite and start reading the manual.
So, if I correctly understand, I import the "film" footage within Davinci and the software itself converts automatically the 12-bit log footage into a 16-bit linear color-space. Then - only once I've edited the footage and re-import it in Davinci as XML for fine grading - only at this point I have to set the LUT (Rec.709 or DCP-P3) within Davinci (so I don't need to set these LUTs also on the monitor) and just for non-destructive preview. That's all right?

Many many thanks!

P.S.
rick.lang wrote:Oh my gosh, do you also need a recipe for tea biscuits?
I love zaleti (typical Venetian biscuits)... perfect with tea! ;)))))
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rick.lang

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Re: LUT & Workflow (bmd-log, linear, rec709, dcp-p3...)

PostThu May 09, 2013 4:52 pm

adrjork wrote:Mr. Lang! You are so generous and helpful! Many many thanks!

I've read carefully your reply. Just a doubt:
rick.lang wrote:3) When you want to produce your final deliverables, you make one or more selections from within Resolve to render your output such as a 2K version for cinema projection in 24fps using DCI-P3 and a HD version for broadcast in 23.976fps using Rec.709 colour space. That's the simple overview just so you feel comfortable with the process but you need to download the free Resolve Lite and start reading the manual.
So, if I correctly understand, I import the "film" footage within Davinci and the software itself converts automatically the 12-bit log footage into a 16-bit linear color-space. Then - only once I've edited the footage and re-import it in Davinci as XML for fine grading - only at this point I have to set the LUT (Rec.709 or DCP-P3) within Davinci (so I don't need to set these LUTs also on the monitor) and just for non-destructive preview. That's all right?

Many many thanks!

P.S.
rick.lang wrote:Oh my gosh, do you also need a recipe for tea biscuits?
I love zaleti (typical Venetian biscuits)... perfect with tea! ;)))))
Image


You can choose a LUT when your new project is defined within Resolve... You can use the included BMD Film LUT or something else such as Captain Hook's free LUT. When you export to FCP X, you will export some version of ProRes such as 4:2:2 (HQ) if you want as much detail as possible in FCP X or ProRes LT or ProRes Proxy (one-quarter the size to edit faster). These depend on what you will do in the external editor or effects programs. You need to take a look at the Resolve manual and read more blog and forum posts as there is a lot of information out there.

Thanks for the hint about those tea biscuits. I'll give it a try if I find a recipe! I always change every recipe I use to make it my own so I can't guarantee I shall get it perfect without practice... just like the custom LUTs you will create. Need to do my zaleti research!

Rick Lang
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Adriano Castaldini

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Re: LUT & Workflow (bmd-log, linear, rec709, dcp-p3...)

PostThu May 09, 2013 5:46 pm

It's true: there are a lot of infos in many forums but all people seem to have tech background that I haven't (and often I do not know where to start!)

i.e. AfterEffects can handle icc profiles in Project Settings windows where I can set the Working space (between Rec.709, CIE-RGB, Universal Camera Film, etc.) and choose if I want to Linearize it or not. Once you set it, there is also the View > Simulate Output option (where again I can choose between Rec.709, CIE-RGB, Universal Camera Film, etc.)

Let's start importing BMC_film footage having in mind to render in HDTV style:
1. do I have to set Rec.709 immediately in Project Settings > Working space, or not?
2. to take advantage of BMCC high-dynamic range and 12-bit gamut, should I choose Linearize option or not?
3. what shoud I choose in View > Simulate Output?

And in all this mess (for my poor head), what profile for the monitor?

Again thanks a lot for your precious help-for-newbie!
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rick.lang

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Re: LUT & Workflow (bmd-log, linear, rec709, dcp-p3...)

PostThu May 09, 2013 6:44 pm

adrjork wrote:It's true: there are a lot of infos in many forums but all people seem to have tech background that I haven't (and often I do not know where to start!)

i.e. AfterEffects can handle icc profiles in Project Settings windows where I can set the Working space (between Rec.709, CIE-RGB, Universal Camera Film, etc.) and choose if I want to Linearize it or not. Once you set it, there is also the View > Simulate Output option (where again I can choose between Rec.709, CIE-RGB, Universal Camera Film, etc.)

Let's start importing BMC_film footage having in mind to render in HDTV style:
1. do I have to set Rec.709 immediately in Project Settings > Working space, or not?
2. to take advantage of BMCC high-dynamic range and 12-bit gamut, should I choose Linearize option or not?
3. what shoud I choose in View > Simulate Output?

And in all this mess (for my poor head), what profile for the monitor?

Again thanks a lot for your precious help-for-newbie!


I shall need someone with experience in Adobe After Effects to chime in here since I don't have any experience with that. Thanks.

Rick Lang
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