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Banding artifacts

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Alexander Feichter
Banding artifacts
on Feb 17, 2009 at 11:35:06 am

hi all,

i was recently playing back from final cut (prores hq, hd 1920x1080, 25 fps) and monitoring on a JVC DT-V24L3DU via sdi. in playback mode the system "turned on" an unacceptable banding which in pause completely disappeared. the footage is very low key and has lots of smooth gradients - so the banding was very eyecatching.
stepping frame by frame though the timeline the banding appeared also for a fraction of a second and then went back to a proper quality.
i had the same issues with ram previewing the dpx-sequences in after effects - so it is not a matter of the prores codec.

the monitor itself on a avid ds worked fine - no artifacts.

on http://www.schallundrauch.tv/banding i put three frames which even in 8 bit jpeg quality are free of banding-artifacts. i also added versions of them which give an idea of how the banding looked like.


thanks for any feedback

alex

system: mac pro, final cut studio 2, decklink hd extreme




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Sean Donnelly
Re: Banding artifacts
on Feb 17, 2009 at 6:05:34 pm

Are you playing back in Dynamic quality? That doesn't look like anything I've ever seen a BM card cause. Having it appear on a still frame while stepping and then correct itself also sounds like a dynamic (or adaptive in AE) problem.

-Sean





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Alexander Feichter
Re: Banding artifacts
on Feb 17, 2009 at 6:37:02 pm

thanks for the quick answer!

i can certainly remember that dynamic quality was switched off and within ae i never use the adaptive resolution feature.

what monitoring device are you using and do you have tried to display my footage on your system, maybe?


still looking out for the "bad guy" in the signal-chain...






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Sean Donnelly
Re: Banding artifacts
on Feb 17, 2009 at 7:22:54 pm

I use an eizo CG241 via DVI, or SDI with an HDLink Pro box for most of my work, although sometimes I use a Panasonic TH-50PF9UK plasma. When you say that you simulated the appearance, how exactly did you do that?

-Sean





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Alexander Feichter
Re: Banding artifacts
on Feb 17, 2009 at 7:56:02 pm

the eizo with an hd link will be the next thing to buy, i think. the 30" would be nice...

the "simulation" - i put the frames into shake. brightness to 0.15, a node inbetween to break the concatenation and than brightness to 6.66. the result is more or less the thing i've seen on the 24".
the banding borders were even sharper i would say...






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Sean Donnelly
Re: Banding artifacts
on Feb 17, 2009 at 8:56:25 pm

Sounds to me like a bit depth conversion problem, I'd say try converting the footage to the BM RGB 10 bit codec and see if it goes away. Also, check and make sure your FW is up to date in the card by downloading the latest installer from the BM website. The EIZO works very well, especially with the HDLINK pro for monitoring LOG footage on set, although it does still suffer from off angle black lift like many other LCD's.

-Sean





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Alexander Feichter
Re: Banding artifacts
on Feb 17, 2009 at 9:11:40 pm

thanks - i will check this out!

alex



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