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Shooting a monitor - how to remove strange rainbow flicker / scan line using AE

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Gus Howard
Shooting a monitor - how to remove strange rainbow flicker / scan line using AE
on Sep 2, 2018 at 6:03:56 am

I shot a computer screen at an angle (4K RED using a Canon lens) and there is a rainbow stripe through it. Is there anyway using After Effects to remove this? I actually also pull focus during the shot, so the the rainbow line moves across the screen as the focus changes. Wondering if there is any semi-easy fix for this? I've tried to minimize with coloring, but - - Any thoughts on a solution to make the shot look a little nicer would be sincerely appreciated.



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Andrew Somers
Re: Shooting a monitor - how to remove strange rainbow flicker / scan line using AE
on Sep 2, 2018 at 11:23:50 am

Because you're shooting a computer screen closeup, I think this is similar to a Moiré artifact. What I think is happening is the detail of the LCD pixels is interfering with whatever debayering algorithm you are using, resulting in the rainbow red artifacts.

Normally the way to get rid of Moiré in an RGB image is to use a notch filter, but I don't know how you'd do that with a RAW image that has not be debayered yet — I don't see such a setting in Redcine...

MAYBE: If you export separate Red, Green, and Blue (mono channels, turning down the other two color completely) and then combine them as separate layers...

If you can upload a single frame, I could experiment with it...

Andrew Somers
VFX & Title Supervisor
http://www.GeneralTitles.com


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Tim Drage
Re: Shooting a monitor - how to remove strange rainbow flicker / scan line using AE
on Sep 3, 2018 at 11:57:37 am

yeah but he NEVER said he wanted any of that? where did you get they idea that the aim was 'matching the original'? obviously he wants it to be a shot of something on a screen FOR EFFECT


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Tim Drage
Re: Shooting a monitor - how to remove strange rainbow flicker / scan line using AE
on Sep 3, 2018 at 12:00:49 pm

I'd make a matte of the effected area, use it to apply some subtle median/minimax/blur combo, some kind of re-colour (eg tint/tritone maybe) it to match the orange and then grain to match the footage. I guess you will probably have to manually roto the matte rather than any kind of tracking


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Kalleheikki Kannisto
Re: Shooting a monitor - how to remove strange rainbow flicker / scan line using AE
on Sep 3, 2018 at 5:36:59 pm

Channel mix (25 red 75 green) for luminosity and masked solids for color give you this. The rainbow effect is gone, but the focus area is still darker than the rest. Will moire again at anything other than 100% resolution, so better evaluated at actual size.



The way this is set up currently only works for these two colors. Little hard to predict from a still image how well it will work on footage. AE file linked below.

12691_screenfix.aep.zip

Kalleheikki Kannisto
Senior Graphic Designer


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Gus Howard
Re: Shooting a monitor - how to remove strange rainbow flicker / scan line using AE
on Sep 3, 2018 at 10:21:25 pm

Thank you so much for the help!! Will be playing with this tonight and let you know how it comes together.


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Michael Szalapski
Re: Shooting a monitor - how to remove strange rainbow flicker / scan line using AE
on Sep 4, 2018 at 6:39:32 pm

For what it's worth, I kinda like that look. It makes it seem much more realistic (because it is).

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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