Yes in all fairness the company never got to the real cause of the fault, but
thought it was a cable and it may not have even been an alexa but another high
end camera, however caused though it did result in 1/2 res red and blue
channels which were unfixable without a more sophisticated version of the
solution I outlined.
Hopefully getting back to source will fix it, if not then it will be the 2nd
time I have come across this.
Howard
>________________________________
> From: Holger Hummel|Celluloid VFX <[email protected]>
>To: Nuke user discussion <[email protected]>
>Sent: Tuesday, 3 July 2012, 21:06
>Subject: Re: [Nuke-users] Artefact Issues with Greenscreen Alexa (ArriRaw)
>
>
>Hi all,
>
>what Alex said is probably a good option.
>i chatted to a friend of mine who's close to all the technical camera-related
>stuff.
>his answers in short form:
>
>1) wrong cabling would most likely result in wrong colors
>2) check which camera firmware and recorder was used
>3) check which ArriRaw Converter version was used, 2.3 being the newest -
>since today, actually (that link you already got from Alex)
>
>last but not least, post it on the official Arri forum. there's a chance of
>having someone from Arri reply to it
>
>http://forum.arridigital.com/forum/
>
>cheers,
>Holger
>
>
>Aélis Héraud wrote:
>> Hi Howard, hi Alex
>>
>> Thanks for the tips guys, we tried the TVIscale, that seems to help a bit
>> more than bluring the red channel, we're still looking for a lossless
>> solution but the TVIscale could be our best option so far.
>> We're waiting for some original Arriraw footages in order to test the
>> Arriraw converter.
>>
>> I'll give you feedback if we find a way to fix the problem.
>>
>> Thanks again,
>>
>> Aélis
>>
>> On 6/29/2012 11:02 AM, Howard Jones wrote:
>>> I had something similar once - where a cable had been plugged in wrong.
>>> Basically both R and B were 1/2 res blown up to full size. ie like proxies.
>>> The quick solution was to rescale to 1/2 res at impulse then resize with a
>>> better filter. It worked to a fashion.
>>> I didn't try TVIscale but that might be worth a go.
>>>
>>> Assuming that is the issue of course. The blue has been rubbish on a number
>>> of shots for me too.
>>>
>>> Howard
>>>
>>> ------------------------------------------------------------------------
>>> *From:* Aélis Héraud <[email protected]>
>>> *To:* [email protected]
>>> *Sent:* Friday, 29 June 2012, 15:26
>>> *Subject:* [Nuke-users] Artefact Issues with Greenscreen Alexa
>>> (ArriRaw)
>>>
>>> -- Okay, I had some trouble sending this mail last night so I
>>> hope you'll receive it now. Sorry for duplicates copies. --
>>>
>>> Hi folks, I'd like to ask you something.
>>>
>>> We have to deal with some greenscreens in Alexa and I know some
>>> people have had some trouble with it. Overall the greenscreens
>>> are pretty good and we're able to get a good result, but we
>>> noticed something on the data and I'd like to have your say on
>>> this matter.
>>>
>>> We noticed some artefacts in the Red and Blue channels,
>>> especially on the thinner blond hairs.
>>> The plates are in 2880x1620, it was recorded in ArriRaw (via
>>> T-Link) and then converted in DPX (Colorspace AlexaV3LogC) so
>>> it's pretty much the best quality we can have, there's no
>>> compression.
>>>
>>> RGBsamplesAlexaArriRaw.png
>>>
>>> As you can see the RGB seems pretty much ok and the green channel
>>> is good, but the red one has some pixels in staircase and I won't
>>> even talk about the blue one. The last picture is a first key.
>>>
>>> After some investigations we're pretty sure it has something to
>>> do with the debayering process. It's maybe due to the algorithm,
>>> the interpolation between pixels isn't very good in the red and
>>> blue channel. I don't know exactly but that's the only
>>> explanation we could come up with so far.
>>>
>>> My question is : Is there a way to fix it in Nuke without
>>> altering the data (the good one) or are we stuck with that ? Any
>>> idea ?
>>>
>>> I tried to split the channels and to put a blur at 1 on the Red
>>> one and it seemed to help a bit at first but eventually we can
>>> feel the softness and we lose the thinner hairs, which I'd like
>>> to avoid. I'd keep that as my last option.
>>>
>>> Our other option would be to ask the company who did the
>>> debayering but I'd like to find another way.
>>>
>>> Thanks for the help
>>>
>>> Aelis
>>>
>>> _______________________________________________
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>>> <mailto:[email protected]>,
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>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
>>>
>>>
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>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
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>
>-- Holger Hummel - [email protected]
>
>Celluloid Visual Effects, Paul-Lincke-Ufer 39/40, 10999 Berlin
>phone +49 (0)30 / 54 735 220 - [email protected]
>
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>
>
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