I set the deck to generate bars. 444 RGB Dual Link being fed to the Kona3 card. I then digitized a bit using the AJA VTR Xchange application to the AJA LogRGB codec and the AJA RGB codec set to Full Range. I then converted those to DPX files and checked the values. The white came in at 940 and the black came in at 64. Just like I would expect.
Then I did the same test in MCv6 using the 1:1 10b RGB MXF setting. That material I exported to QTs using both the AJA LogRGB codec and the AJA RGB codec set to Full Range. I then converted those to DPX files and checked the values. The white came in at 1023 and the black came in a 0. Not good. Looks like I'll continue to use VTR Xchange and FCP7 for my element capture and conforms.
I think that the problem goes back to an article that Avid had on the knowledge base, but has pulled. It was at
http://avid.custkb.com/avid/app/selfservice/search.jsp?DocId=385691&NewLang=en
But is now gone. It basically stated that if you were getting QTs from the Alexa camera that were recorded in Log then your camera is broken and you need to contact Arri to fix it. Oh I wish they still had that up. It was so ridiculous. But my hope is that if they pulled it then they have realized that this is something they need to address.
Jay
On Dec 16, 2011, at 8:24 PM, johnrobmoore wrote:
> What does capturing Smpte bars look like on the scope. I haven't dealt with 444 but what is the spirit of RGB 709? I think of RGB as full 0 to 255 or 0 to 1023 and 709 as 16 to 235 or 64 to 940. Clearly I'm missing something about these projects. What does the AJA Log RGB codec to the footage. Does that act like a lut to make linear our of log or does the footage look washed out like log footage does sometimes?
>
> --- In Avid-L2@yahoogroups.com, Jay Mahavier <jay_mahavier@...> wrote:
>>
>> For the past few projects we have off-lined in Avid Media Composer and then did our conform in FCP7. Our sources have been HDSR tape, 1080 23.98 444 RGB with a Log source. Panavision Genesis or Arri Alexa. When doing element capture or the conform we would use the FCP7 system with a Kona3 card. Capture using the AJA Log RGB codec, full range (0-1023). Bottom line of that was pixel in = pixel out. What I digitized was a match to what was on tape. I could digitize, insert edit back to the tape, and then digitize again and it was a pixel to pixel match on the resulting digitized footage.
>>
>> So I was interested in how MC6 would compare. I set up a test system running MCv6 on OSX 10.7.2 with a Kona3 card using AJA drivers v10.0.1.
>>
>> I digitized a few shots in the original FCP7 system as a base line. Then on the MC6 Test system I used the AJA VTR Xchange application to capture footage. Different CPU, different Kona card, and different source SR deck then I used for the FCP 7 system, but same source tape and same section of footage. The footage matched between the two systems.
>>
>> Then I launched MCv6. Made a new Avid project. 1080/23.98 RGB. I did capture test with 1:1, DNxHD, and ProRes4444. And none of them match the footage from either the FCP7 system or the test I did on the Avid system using AJA VTR Xchange. I think the problem is that the Color Space setting for the Avid project is RGB 709. The 709 part being the problem. To capture Log footage I need full range RGB capability. Rec 709 just won't do. It looked like what MC6 was doing was actually taking 64 (16) and moving it to 0 and taking 940 (235) and moving it to 1023. I think that's what's going on. At least when I start pixel probing the values and looking at histograms that's what appears to be happening. But maybe I have a setting wrong somewhere in MC6.
>>
>> I'm not sure if there are plans to fix this or not. But I sure hope they do. I would really like to be able to do my element capture and conform on Media Composer.
>>
>> If anyone has any observations about this they would like to share I would like to hear them.
>>
>> Thank you,
>> Jay
>>
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