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ALexa ProRes4444 LogC workflow question
I’ve been handed some materials from a test shoot of an Arri Alexa. They shot to SR 444 RGB and ProRes4444 at the same time. There was some greenscreen footage shot as part of the test and there are some VFX guys who want to get their hands on it. They work with DPX and TIFF regularly, but they don’t use QTs. So I need to get them file sequence for them to do a comparison. I know how to do this from the SR tape as I do it all the time. But how and to which file format should I convert the ProRes material to?
I tried using Compressor and the DPX and TIFF that are produced look very different from the QT.
In FCP I put the ProRes file onto a sequence set to AJA 10bit log RGB and exported and then used QTtoDPX and that looked yet different.
I think that part of the problem is that the tools I have assume DPX to be 10bit, while the ProRes4444 is 12bit. I’m not sure what’s up with the TIFF looking different.
Any assistance for direction would be very appreciated.
Thank you,
Jay Mahavier -
14 Replies
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Hey Jay,
Is this Art’s test?
First the ProRes from Alexa currently is Y’Cb’Cr not RGB, the current Alexa build that allows PropRes capture does not allow RGB capture to the SxS cards at this time.
the ProRes is also limited to 10bit until the next software rev of the camera.The Aja Qt – Dpx converter should not have any issues converting to DPX-
gary adcock
Studio37Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, ILhttps://blogs.creativecow.net/24640
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I don’t believe this is Art’s test. I don’t know an Art. But anyway, I’m still confused as to how to work with the ProRes4444. I need to be able to make either a DPX for TIFF sequence for VFX. And it has to be something that I should be able to bring back any frame into the DI system and cut in and not see a shift between it and the frames around it. Do you have any suggestions on how to get this to work or is this one of those things that I won’t be able to do until a future release of the software?
Thank you for the help on this.
Jay
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Gary:
I caught your reply on the Arri forum. Thank you for covering this. I’m still looking forward to going file based someday. Each project gets closer. But this next one probably won’t be it I guess. But soon.
Thank you again.
jay
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[Jay Mahavier] “I’m still confused as to how to work with the ProRes4444. I need to be able to make either a DPX for TIFF sequence for VFX.”
Agreed, but since ProRes Recording is technically not yet enabled on the camera, we have some time.
Most high end workflows now support ProRes (Baselight, Nucoda, Scratch and the Autodesk tools) this request may reduce as time goes on. Most of the highend workflow I know of assume that most of VFX houses are really waiting for the ArriRaw to give them the greatest latitude.
I have been successful in using AE to generate the DPX/ Cineon frames correctly, Compressor will need a couple of hoops adjusted to handle the file correctly.
The whole point of going directly to ProRes is to bypass the conversion process- which is fraught with math errors in the conversions.
[Jay Mahavier] “I don’t believe this is Art’s test. “
I was not sure- there are very few of the cameras that have been configured to handle the DTE workflow as of yet, I know for a couple of weeks I had access to the only one outside of arri that was configured for DTE.
gary adcock
Studio37Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, ILhttps://blogs.creativecow.net/24640
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Yea, ArriRaw sounds very cool. With the Codex transfer station for extracting to different formats. Very nice. We were told it should be working on the Alexa very soon, but that “very soon” is about half way through our next production. Thank you again for all the insight.
Jay
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[Jay Mahavier] “We were told it should be working on the Alexa very soon, but that “very soon” is about half way through our next production”
Yeah tell me about it.
next time you talk to Mike Bravin ask for my phone number. You’re down south of me and you never know when I might be able to help.
gary
gary adcock
Studio37Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, ILhttps://blogs.creativecow.net/24640
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[gary adcock] “First the ProRes from Alexa currently is Y’Cb’Cr not RGB, the current Alexa build that allows PropRes capture does not allow RGB capture to the SxS cards at this time.”
How would one tell? I have a bunch of Alexa footage in ProRes 4444. What is a quick way to tell whether it is RGB or YCbCr?
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[Michael Aranyshev] “How would one tell? I have a bunch of Alexa footage in ProRes 4444. What is a quick way to tell whether it is RGB or YCbCr?”
I used a spectrum analyzer from Tektronix, it is neither cheap nor quick.
It is my understanding that issue was only with the specific build on the cameras I was testing and that later release versions support both formats. I do not have confirmation from Arri (August is holiday time in Europe) .
I am going to go out on limb and assume that if you are shooting as Rec 709 you will be working with YCbCr materials since you have defined that material by working in the Video Rec, while if you are recording LogC you should be working with RGB content on the SxS cards.
gary adcock
Studio37Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, ILhttps://blogs.creativecow.net/24640
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If I remember correctly the build you tested had ProRes 4444 disabled. In ours it is enabled but the LogC is still grayed out.
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[Michael Aranyshev] “If I remember correctly the build you tested had ProRes 4444 disabled. In ours it is enabled but the LogC is still grayed out.”
Nope- that was not me- I had one of the only fully operational cameras with SxS recording fully enabled that were in the US at the time. ( go back in my blog- there is even a video walkthru of the camera that clearly shows that everything IS working)
If LogC is grayed out- you have the Project menu incorrectly set to record content only as Rec 709.
Setting the Project Menu to LogC allows both the Monitor and Record OUT to be either Rec 709 or LogC on either or both outputs, whereas setting the Project Menu settings to Rec709- effectively locks your recording and monitoring into the Rec 709 video space.
gary adcock
Studio37Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, ILhttps://blogs.creativecow.net/24640
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